United States: Prescription Medical Product Causation – Expert Required – Part One

Last Updated: August 14 2019
Article by James Beck

We recently blogged about the final chapter (at the district court level, anyway) of the big defense win in the Mirena MDL. The long-overdue result was entry of summary judgment for the defendant against all claims. As the blog also chronicled, the key Mirena decision had been earlier – and was already appealed and affirmed – Daubert required exclusion of the plaintiffs' general causation experts.

We're not revisiting that today. However, in reading the recent opinion, though, we noticed this:

As an appendix to its submissions in support of its motion for summary judgment, [defendant] has supplied citations to hundreds of cases from . . . 53 jurisdictions. . . . [Defendant] cites this authority to support . . . the argument[s] . . . that general causation is an element of complex products liability tort claims, and . . . that general causation in such cases requires proof in the form of expert testimony. . . . The Court is persuaded that every jurisdiction requires a showing of general causation in cases, like this one, in which a plaintiff alleges that the use of a product gave rise, through a complex causal mechanism, to a medical injury or impairment.

In re Mirena IUS Levonorgestrel-Related Products Liability Litigation (No. II), ___ F. Supp.3d ___, 2019 WL 2433552, at *9 n.2 (S.D.N.Y. June 11, 2019) (emphasis added).

Well, well well. . . . A collection of cases requiring expert testimony in "complex" causation product liability cases from 53 jurisdictions? Sounds like something right up the DDLaw Blog's alley. It's a publicly filed document, we have a PACER account, and we know how to use it. So we located and downloaded the aforementioned appendix, and used it as the starting point for this post – and it was a very good starting point, indeed (kudos to defense counsel's research) – for the 50-state survey that follows.

We've endeavored to collect as many no-expert prescription medical product liability litigation dismissals as we could find, as well as similar decisions in other product liability and toxic tort cases. Along with selected caselaw from every state, we've produced fifty states' worth of precedent that, we hope, means that none of our clients will ever have to start from scratch again, should they feel the need to present similar research in support of the expert witness requirement that prevailed in Mirena – that all states require dismissal of prescription medical product liability plaintiffs who lack admissible expert witnesses.

To start, we found a number of cases, some mentioned in the Mirena opinion, holding broadly that "every state in the union" – or some equivalent phrase − require expert-based evidence in complex product liability cases, concern causation and/or defect issues. First, of course, there is Mirena itself: "all relevant jurisdictions require some evidence of general causation in products liability cases involving complex products liability (or medical) issues." 2019 WL 2433552, at *9.

It is well established that expert testimony is required to establish causation where the issue of causation is beyond the knowledge of lay jurors. Other courts, surveying the law of the 50 states and territories, have concluded that each jurisdiction typically adheres to this principle.

* * * *

[G]enerally in products liability cases involving complex causation issues, including cases involving pharmaceuticals or medical devices, to establish causation, plaintiffs must offer admissible expert testimony regarding both general causation and specific causation. There are many holdings in accord.

Id. at *11-12 (citations and quotation marks omitted).

[A]ll jurisdictions have a similar rule requiring expert testimony where a matter is outside the ken of an ordinary lay juror. Because [the product] is a medical device and the theory of secondary perforation is a concept requiring a nuanced understanding of . . . anatomy, the Court has no serious doubt that all jurisdictions would treat this issue as one requiring expert testimony to prove causation.

In re Mirena IUD Products Liability Litigation, 202 F. Supp.3d 304, 313 (S.D.N.Y. 2016), aff'd, 713 F. Appx. 11, 16 (2d Cir. 2017) ("Plaintiffs have not identified any state that does not require expert testimony in the circumstances at issue here"). See also Barnes v. Anderson, 202 F.3d 150, 159 (2d Cir. 1999) ("[t]he requirement that plaintiffs produce expert medical evidence in order to prove proximate causation of medical injury also is often expressed") (applying federal law); In re Lipitor Marketing, Sales Practices & Products Liability Litigation, 227 F. Supp.3d 452, 469 (D.S.C. 2017) ("While the specific language used by courts varies to some degree, all jurisdictions require expert testimony at least where the issues are medically complex and outside common knowledge and lay experience."); In re Lipitor (Atorvastatin Calcium) Marketing, Sales Practices & Products Liability Litigation, 226 F. Supp.3d 557, 569-70 (D.S.C. 2017) (same); In re Zoloft (Sertralinehydrochloride) Products Liability Litigation, 176 F. Supp.3d 483, 490 (E.D. Pa. 2016) ("Plaintiffs have not cited cases from any jurisdiction holding that the complex scientific question of whether a prescription drug is a teratogen can be answered without expert testimony or based on circumstantial evidence, and the legal principles upon which the Court has relied tend to be consistent across jurisdictions."), aff'd, 858 F.3d 787 (3d Cir. 2017); In re Bausch & Lomb, Inc. Contacts Lens Solution Products Liability Litigation, 693 F. Supp.2d 515, 518 (D.S.C. 2010) (Under the law of "all the applicable jurisdictions," "plaintiffs' claims cannot survive" after "plaintiffs' only general causation expert, has been excluded."), aff'd, 429 F. Appx. 249 (4th Cir. 2011); In re Rezulin Products Liability Litigation, 441 F. Supp.2d 567, 575 & n.68 (S.D.N.Y. 2006) (expert causation testimony in prescription medical product liability litigation "is a requirement in every state in which these plaintiffs have brought their claims"); In re Phenylpropanolamine (PPA) Products Liability Litigation, 2003 WL 27382559, at *1 (W.D. Wash. Oct. 24, 2003) ("Given the medically and scientifically complex nature of this litigation, expert testimony is crucial to the establishment of causation."); In re Norplant Contraceptive Products Liability Litigation, 215 F. Supp.2d 795, 830, 833 (E.D. Tex. 2002) ("[e]vidence of general causation must be provided in the form of expert testimony"; summary judgment granted; "Plaintiffs have not produced a shred of evidence or expert testimony that supports an association between Norplant and any of the [more than 950] exotic conditions").


Anyway, as our research often does, this project became much more substantial than we originally expected. The law was more extensive than we thought, and to do it justice required going beyond prescription medical product liability litigation. So in order not to overwhelm our readers with too much at once, we've decided to break this 50-state survey – at least initially – into three roughly equal parts. Part one is Alabama through maritime law.


Under Alabama law, expert testimony is required to establish causation where "the nature and origin" of the injury is "beyond the understanding of the average person." Ex parte Trinity Industries, Inc., 680 So.2d 262, 269 (Ala. 1996). Thus, "[p]laintiffs must prove the toxicity of [a product] and that it had a toxic effect on them causing the injuries that they suffered," and "[t]his type of proof requires expert testimony." McClain v. Metabolife International, Inc., 401 F.3d 1233, 1237 (11th Cir. 2005) (applying Alabama law).

The interaction between a complex and technical medical device and the unique physiological and medical circumstances of the patient in which it is implanted is a subject on which no ordinary juror could rationally be expected to have knowledge. The net result is that, without the benefit of expert testimony, a reasonable jury could not possibly make a determination . . . that [plaintiff's] injuries were caused by a . . . defect in the [product].

Hughes v. Stryker Sales Corp., 2010 WL 1961051, at *5 (S.D. Ala. May 13, 2010), aff'd, 423 F. Appx. 878, 881 (5th Cir. 2011) (on basis of district court's reasoning). "[I]n the typical case involving a complex medical device, the absence of expert testimony would force a jury to engage in speculation and conjecture on issues of defect and causation," thus "courts routinely require expert testimony in such matters." Id.

Thus, "Alabama courts consistently have opined that . . ., when the product at issue is of a complex and technical nature, the plaintiff's proof of a defect should be in the form of expert testimony. Bloodsworth v. Smith & Nephew, Inc., 476 F. Supp.2d 1348, 1353 n.3 (M.D. Ala. 2006). See Drake v. Ortho-McNeil-Janssen Pharmaceuticals, 2018 WL 1431646 (N.D. Ala. March 22, 2018) ("[d]ue to the complex nature of the claims, expert testimony generally is required to establish general and specific causation in product liability cases"); Brantley v. International Paper Co., 2017 WL 2292767, at *16 (M.D. Ala. May 24, 2017) ("The plaintiffs must establish both general and specific causation through expert evidence."); Jones v. Novartis Pharmaceuticals Corp., 2017 WL 553134, at *17 (N.D. Ala. Feb. 10, 2017) ("plaintiffs must provide expert testimony to establish both general and specific causation"), aff'd, 720 F. Appx. 1006 (11th Cir. 2018); Benkwith v. Matrixx Initiatives, Inc., 467 F. Supp.2d 1316, 1332 (M.D. Ala. 2006) (plaintiff "must present expert evidence on general causation. Without proof of causation, she cannot prevail") (citation omitted); Sutherland v. Matrixx Initiatives, Inc., 2006 WL 6617000, at *14 (N.D. Ala. 2006) ("without an expert to connect a toxin to an injury, there is no toxic tort"); Emody v. Medtronic, Inc., 238 F. Supp.2d 1291, 1295 (N.D. Ala. 2003) ("An essential element of all product liability cases is expert testimony . . . that a defect was the medical cause of plaintiff's claimed injuries.").


Expert testimony is required in Alaska to establish a causal connection "where there is no reasonably apparent . . . causal relationship between the event demonstrated and the result sought to be proved." Choi v. Anvil, 32 P.3d 1, 3 (Alaska 2001) (citation and quotation marks omitted). This question is one "of law to which we apply our independent judgment." D.P. v. Wrangell General Hospital, 5 P.3d 225, 228 (Alaska 2000). Thus, a plaintiff is "required by law to support his claim with expert testimony unless the causation of his alleged injury was of a non-technical nature." Parker v. Tomera, 89 P.3d 761, 766 (Alaska 2004). See Voyles v. State, 2008 WL 4951416, at *18 (Alaska App. Nov. 19, 2008) ("The test is whether the basis of the [casual] conclusion (once explained) can be readily understood and assessed by lay jurors."); Coppe v. Bleicher, 2008 WL 8614177 (Alaska Super. Aug. 29, 2008) ("Expert testimony is required to establish medical causation when the nature and character of a person's injuries require the special skill of an expert to render the evidence comprehensible."); Gallant v. United States, 392 F. Supp.2d 1077, 1080-81 (D. Alaska 2005) (expert testimony required in any case that "is not a situation where negligence could be evident to a lay person") (footnote omitted).


In Arizona litigation, "[w]hen [a] causal connection is not readily apparent, it must be established by expert medical testimony" Aguayo v. Industrial Commission, 333 P.3d 31, 33-346 (Ariz. App. 2014). Thus, "[w]here causation is peculiarly within the knowledge of medical experts . . . we must rely upon the opinion of medical experts." McNeely v. Industrial Commission, 501 P.2d 555, 557 (Ariz. 1972). "Expert medical testimony is . . . generally required to establish proximate cause unless a causal relationship is readily apparent to the trier of fact." Rasor v. Northwest Hospital, LLC, 373 P.3d 563, 566 (Ariz. App. 2016), rev'd on other grounds, 403 P.3d 572 (Ariz. 2017) (holding plaintiff's expert unqualified). See also Clemens v. DMB Sports Clubs Ltd. Partnership, 2015 WL 8166584, at *3 (Ariz. App. Dec. 8, 2015) ("the plaintiff must prove the cause of . . . physical injury damages through expert medical testimony, unless a causal relationship is readily apparent to the trier of fact") (citation and quotation marks omitted); Gentry v. Daugherity, 2015 WL 1346097, at *3 (D. Ariz. March 24, 2015) ("Unless an injury is obvious to the jury, expert medical testimony is required to establish the nature and extent of the injury as well as its relationship to the accident."); Cloud v. Pfizer, Inc., 198 F. Supp.2d 1118, 1138-39 (D. Ariz. 2001) (a plaintiff "cannot prove causation" "in the absence" of expert testimony).


Arkansas requires expert testimony regarding causation in the "vast majority of our cases" where it involves medical issues that are "not within the comprehension of a jury of laymen." Mitchell v. Lincoln, 237 S.W.3d 455, 599 (Ark. 2006). "Except in the most obvious cases, such causation must be established by expert medical testimony." Baldwin v. Club Products Co., 604 S.W.2d 568, 570 (Ark. App. 1980). Where a plaintiff's "alleged resulting injuries involved complex medical issues outside the jury's common knowledge, . . . expert testimony was necessary." Engleman v. McCullough, 535 S.W.3d 643, 649 (Ark. App. 2017).

In product liability "to prove a defect by showing a safer alternative design . . . [plaintiff] could not meet his burden without an expert." Anderson v. Raymond Corp., 340 F.3d 520, 524 (8th Cir. 2003) (applying Arkansas law). Thus, "Whether proceeding on a negligence or strict liability theory, a plaintiff in a toxic tort case must, under Arkansas law, establish medical causation through expert testimony." National Bank of Commerce v. Associated Milk Producers, Inc., 22 F. Supp.2d 942, 949 (E.D. Ark. 1998), aff'd, 191 F.3d 858 (8th Cir. 1999). "Under Arkansas law, expert witness testimony is required to prove that any negligence of Defendants was a proximate cause of Plaintiff's injuries, as Plaintiff in this case alleged medical injuries based on a theory that involved complex determinations of medical issues." Isham v. Booneville Community Hospital, 2015 WL 4133098, at *2 (W.D. Ark. July 8, 2015).


California law establishes that "the decisive consideration in determining the necessity of expert opinion evidence is whether the subject of inquiry is one of such common knowledge that persons of ordinary education could reach a conclusion as intelligently as the witness or whether, on the other hand, the matter is sufficiently beyond common experience that the opinion of an expert is required." Campbell v. General Motors Corp., 649 P.2d 224, 231 (Cal. 1982). "In cases like the one before us, presenting complicated and possibly esoteric medical causation issues, the standard of proof ordinarily required is 'a reasonable medical probability based upon competent expert testimony that the defendant's conduct contributed to [the] plaintiff's injury.'" Bockrath v. Aldrich Chemical Co., 980 P.2d 398, 403 (Cal. 1999) (quoting Rutherford v. Owens-Illinois, Inc., 941 P.2d 1203, 1219 n.11 (Cal .1997)). Where "the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation." Stephen v. Ford Motor Co., 37 Cal. Rptr.3d 9, 17 (Cal. App. 2005). See Miranda v. Bomel Construction Co.,. 115 Cal. Rptr.3d 538, 545-46 (Cal. App 2010) ("The law is well settled that in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony."); People v. Racy, 56 Cal. Rptr.3d 455, 460 (2007) ("expert testimony would have been necessary because the effects of [the product] . . . are matters beyond the experience of average jurors"); Jones v. Ortho Pharmaceutical Corp., 209 Cal. Rptr. 456, 461 (Cal. App. 1985) ("the unknown and mysterious etiology of cancer" is "beyond the experience of laymen and can only be explained through expert testimony").

Thus, "In California, 'in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.'" Avila v. Willits Environmental Remediation Trust, 633 F.3d 828, 836 (9th Cir. 2011) (quoting Jones, 209 Cal. Rptr. at 460).

The law is well-settled that in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony. And where, as here, the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation.

Brown v. Johnson & Johnson, 2019 WL 2577296, at *5 (E.D. Cal. June 24, 2019) (citations and quotation marks omitted). See Nelson v. Matrixx Initiatives, Inc., 592 F. Appx. 591, 592 (9th Cir. 2015) ("General and specific causation" "must be proven within a reasonable medical probability based upon competent expert testimony.") (also quoting Jones) (applying California law); Pierson v. Ford Motor Co., 445 F. Appx. 966, 968 (9th Cir. 2011) (quoting Stephen) (applying California law); In re Baycol Products Litigation, 596 F.3d 884, 889 (8th Cir. 2010) ("To succeed in his strict liability and negligence claims, [plaintiff] has the burden of proving medical causation through the use of a medical expert.") (citing Bockrath) (applying California law); Shalaby v. Newell Rubbermain, Inc., 379 F. Appx. 620, 623 (9th Cir. 2010 (where "the plaintiffs had not presented the expert testimony required to establish causation . . ., the plaintiffs had not established a prima facie case") (quoting Stephen) (applying California law); Viramontes v. Pfizer, Inc., 2018 WL 3363699, at *9 (E.D. Cal. July 10, 2018) ("The applicable law requires that 'in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.'") (also quoting Jones); Sclafani v. Air & Liquid Systems Corp., 14 F. Supp.3d 1351, 1355 (C.D. Cal. 2014) (issues of causation "beyond the experience of laymen . . . can only be explained through expert testimony"); Thomas v. Abbott Laboratories, 2014 WL 4197494, at *11 (C.D. Cal. July 29, 2014) ("Where causation is beyond a jury's experience, it is the expert who must rule out the other possible causes."); Sanchez v. Stryker Corp., 2012 WL 1570569 at *6 (C.D. Cal. May 2, 2012) ("Probable causes in a medical tort case are beyond the experience of laymen and can only be explained through expert testimony."); Cox v. Depuy Motech, Inc., 2000 WL 1160486, at *7 (S.D.Cal. March 29, 2000) ("Because plaintiff does not have an expert who can establish medical causation, an essential element of a products liability claim, plaintiff cannot withstand defendant’s motion for summary judgment on the issue of causation."); Huntman v. Danek Medical, Inc., 1998 WL 663362, at *3–4 (S.D.Cal. July 24, 1998) ("[i]n the absence of expert testimony . . . plaintiff's strict liability and negligence claims must fail"); Sanderson v. International Flavors & Fragrances, Inc., 950 F. Supp. 981, 985 (C.D. Cal. 1996) ("It should be emphasized that expert testimony is required to establish causation, since this case involves scientific issues that are beyond the experience of laymen.").


Under Colorado law, when "the applicable standard is not within the common knowledge and experience of ordinary persons, the applicable standard must be established by expert testimony." United Blood Services, a Div. of Blood Systems, Inc. v. Quintana, 827 P.2d 509, 520 (Colo. 1992). Expert testimony is required for any "complex medical question outside lay competence." Mathison v. United States, 619 F. Appx. 691, 694 (10th Cir. 2015) (applying Colorado law).

Thus, "[u]nder Colorado law, products liability claims involving matters outside the experience of the average layperson, like negligence claims involving such complex or technical issues, require expert testimony to prove issues such as causation." Xtreme Coil Drilling Corp. v. Encana Oil & Gas (USA), Inc., 2010 WL 3777303, at *7 (D. Colo. Sept. 19, 2010). Thus, Colorado law "require[s] expert witness testimony to establish the causal link between complex injuries and [an] incident." Sanchez-Ironshell v. Brinker Restaurant Corp., 2017 WL 5990090, at *3 (D. Colo. June 15, 2017). See Truck Insurance Exchange v. MagneTek, Inc., 360 F.3d 1206, 1215 (10th Cir. 2004) ("without the excluded expert testimony . . ., a jury could not reasonably make the necessary inference that the [product] caused the [accident]") (applying Colorado law); Brown v. Johnson & Johnson, 2016 WL 897021, at *1 (D. Colo. March 9, 2016) ("these injuries were allegedly caused by chemicals working within [plaintiff's] body. A lay jury does not have the competence to conclude, based on everyday experience, that [a drug] in fact caused [plaintiff's] injuries."); Howell v. Centric Group, LLC, 2011 WL 4499372, at *5 (D. Colo. Sept. 27, 2011) ("where questions of causation are beyond the knowledge and experience of ordinary persons, expert testimony may be required"), aff'd, 508 F. Appx. 834, 836 (10th Cir. 2013) ("[w]here an injury has multiple potential etiologies, expert testimony is necessary to establish causation") (citation and quotation marks omitted) (applying Colorado law).


In Connecticut, "[i]f lay witnesses and common experience are not sufficient to remove the case from the realm of speculation, the plaintiff will need to present expert testimony to establish a prima facie case." Metropolitan Property & Casualty Insurance Co. v. Deere & Co., 25 A.3d 571, 584 (Conn. 2011). Thus, "[d]epending on the type of product at issue − namely, its complexity − expert testimony regarding product defect or causation may be required in order to make out a prima facie product liability case." D'Ascanio v. Toyota Industrial Corp., 72 A.3d 1019, 1026 (Conn. 2013). Accord Bagley v. Adel Wiggins Group, 171 A.3d 432, 447 (Conn. 2017) ("proof [of asbestos exposure] required the assistance of an expert because the subject matter was technical in nature and beyond the field of ordinary knowledge of a lay juror. Because the plaintiff did not produce an expert, she failed to prove her case."); Santopietro v. City of New Haven, 682 A.2d 106 (Conn. 1996) ("If the determination of the standard of care requires knowledge that is beyond the experience of an ordinary fact finder, expert testimony will be required.").

"When the causation issue involved goes beyond the field of ordinary knowledge and experience of judges and jurors, expert testimony is required." Theodore v. Lifeline Systems Co., 163 A.3d 654, 666 (Conn. App. 2017) (citation and quotation marks omitted). "[W]e . . . consistently have held that expert testimony is required when the question involved goes beyond the field of the ordinary knowledge and experience of judges or jurors." White v. Mazda Motor, Inc., 54 A.3d 643, 650 (Conn. App. 2012) (citation and quotation marks omitted), aff'd, 99 A.3d 1079 (Conn. 2014).

Proof that a defect in the product caused the injury in controversy is a prerequisite to recovery for product-caused injury in every products liability case. . . . When the causation issue involved goes beyond the field of ordinary knowledge and experience of judges and jurors, expert testimony is required. The product at issue in the present case is a complex product: a spinal system . . . implanted into the patient's spine. . . . Accordingly, we agree with the trial court's determination that expert testimony was required to establish causation.

Ferrari v. Johnson & Johnson, Inc., ___ A.3d ___, 2019 WL 2167849, at *6 (Conn. App. May 21, 2019). Accord Milton v. Robinson, 27 A.3d 480, 493 (Conn. App. 2011) (expert testimony mandatory in case that "concerns complex details regarding the adequacy of a phase III clinical study and standards of care in designing experimental drugs").

Thus, "Connecticut courts consistently hold 'that expert testimony is required when the question involved goes beyond the field of the ordinary knowledge and experience of judges or jurors.'" Brown v. Johnson & Johnson Pharmaceuticals, 2015 WL 235135, at *3 (D. Conn. Jan. 16, 2015) (quoting White). "[W]ithout expert medical testimony causally linking [the drug] to [plaintiff's] injuries, a reasonable jury could not find that it is more probable than not that [the drug] caused [those] injuries." Id. at *4. See Grenger v. General Electric Co., 2019 WL 2743577, at *2 (D. Conn. July 1, 2019) (entering summary judgment because "[w]ithout competent expert testimony, plaintiff will be unable to demonstrate" exposure); Beyer v. Anchor Insulation Co., 238 F. Supp.3d 270, 294 (D. Conn. 2017) ("The complexity of the causal link between [the product] and Plaintiffs' health problems necessitates expert testimony as to general causation."); K.E. v. GlaxoSmithKline LLC, 2017 WL 440242, at *26 (D. Conn. Feb. 1, 2017) (summary judgment granted in prescription medical product liability case after plaintiffs' experts excluded); Sullivan v. Pfizer, Inc., 2016 WL 868155, at *4 n.4 (D. Conn. March 4, 2016) ("Because prescription drugs and their effects on the human body are complex issues, Sullivan cannot avoid the need for expert testimony by relying on the doctrine of res ipsa loquitur."); Walters v. Howmedica Osteonics Corp., 676 F. Supp.2d 44, 52 (D. Conn. 2009) ("the standard of care that the designer and manufacturer of [a medical device] must follow lay beyond the experience and ken of the ordinary fact finder"; summary judgment entered for lack of expert testimony) (citation and quotation marks omitted); Koger v. Synthes North America, Inc., 2009 WL 5110780, at *3 (D. Conn. Dec. 17, 2009) ("plaintiff's proof of defect and causation involves complex issues, requiring expert testimony"); Gold v. Dalkon Shield Claimants Trust, 1998 WL 351456, at *3 (D. Conn. June 15, 1998) ("without a proffer of expert medical testimony as to causation to link the defect to the injury, a reasonable jury could not find that the plaintiff has proved that the defect caused her specific injuries"), aff'd, 189 F.3d 460 (2d Cir. 1999).


"It is settled Delaware law that, if a claim requires proof of facts that are "not within the common knowledge of laymen," those facts "must be presented through competent expert testimony." Campbell v. DiSabatino, 947 A.2d 1116, 1118 (Del. 2008). "When the plaintiff's claim involves bodily injuries, the causal connection between the defendant's alleged negligent conduct and the plaintiff's alleged injury must be proven by the direct testimony of a competent medical expert." Roache v. Charney, 38 A.3d 281, 286 (Del. 2012). "[I]f the matter in issue is one within the knowledge of experts only and not within the common knowledge of laymen, it is necessary for the plaintiff to introduce expert testimony in order to establish a prima facie case." Money v. Manville Corp. Asbestos Disease Compensatory Trust Fund, 596 A.2d 1372, 1375 (Del. 1991) (citations and quotation marks omitted).

If a party intends to make an argument involving an issue that is within the knowledge of experts only and not within the common knowledge of laymen, the party must present competent expert testimony to support that argument. Expert testimony is required where a reasoned decision on the question of proximate cause may require understanding and analysis of issues beyond the ken of the typical jury.

Davis v. Maute, 770 A.2d 36, 40 n.3 (Del. 2001) (citations and quotation marks omitted).

Thus, "[i]n pharmaceutical cases such as this, involving complex scientific evidence, a plaintiff must present expert witnesses to provide evidence of both general and specific causation." Scaife v. Astrazeneca LP, 2009 WL 1610575, at *20 (Del. Super. June 9, 2009) (footnote omitted). See Hopkins v. Janssen Pharmaceuticals, Inc., 2019 WL 1567840, at *2 (D. Del. April 11, 2019) (granting summary judgment because "Plaintiff cannot establish proximate cause, as a matter of law, because he has not produced an expert report"); Guinan v. A.I. duPont Hospital for Children, 597 F. Supp.2d 517, 533 (E.D. Pa. 2009) (summary judgment granted where plaintiff's expert's "report is devoid of an opinion regarding causation") (applying Delaware law), aff'd, 393 F. Appx. 884 (3d Cir. 2010); Collis v. Topper's Salon & Health Spa, Inc., 2013 WL 4716237, at *2 (Del. Super. Aug. 29, 2013) ("Medical expert testimony regarding causation is required when there is a claim for bodily injuries, regardless of the nature of the negligence involved."); Gunzl v. Warner's Moving & Storage, Inc., 1993 WL 331084, at *3 (Del. Super. Aug. 4, 1993) ("Medical testimony is necessary to establish causation between the accident and the alleged disability if the medical question becomes sufficiently complicated so that it is within the field of medical experts.").

District of Columbia

District of Columbia litigants must produce expert testimony "in cases presenting medically complicated questions due to multiple and/or preexisting causes." Baltimore v. B.F. Goodrich Co., 545 A.2d 1228, 1231 (D.C. 1988). "Our rule for medically complicated cases is that proof of causation normally requires medical opinion testimony." Lasley v. Georgetown University, 688 A.2d 1381, 1384 (D.C. 1997). "In cases presenting medically complicated questions . . ., we have held that expert testimony is required on the issue of causation." Brin v. S.E.W. Investors, 902 A.2d 784, 793 (D.C. 2006) (quoting Williams v. Patterson, 681 A.2d 1147, 1150 (D.C. 1996)).

Federal courts apply the expert requirement to all defect and causation questions. "D.C. law often requires expert testimony in tort cases even when the facts underlying the plaintiff's injury might seem fairly straightforward." Davis v. Bud and Papa, Inc., 885 F. Supp.2d 85, 89 (D.D.C. 2012). See Westinghouse Electric Corp. v. Nutt, 407 A.2d 606, 612 (D.C. 1979) ("[t]he jury needed supporting expert testimony to assess the burden of precaution to avoid harm"); Kubicki v. Medtronic, Inc., 293 F. Supp.3d 129, 156 (D.D.C. 2018) ("in complex medical product liability cases such as this one, expert testimony regarding causation is ordinarily indispensable under District of Columbia law"); Arias v. DynCorp, 928 F. Supp.2d 1, 9 (D.D.C. 2013) ("Because the nexus between the plaintiffs' exposure and their increased risk of cancer would not be obvious to the jury, expert evidence is required to explain the underlying medical science and avoid jury guesswork or speculation as to the issue of causation."); Halcomb v. Woods, 610 F. Supp.2d 77, 85 (D.D.C. 2009) ("expert testimony is necessary to demonstrate a causal link between a defendant's act and a plaintiff's harm "in cases presenting medically complicated questions"); Willis v. Besam Automated Entrance Systems, Inc., 2005 WL 2902494, at *14 (E.D. Pa. Nov. 3, 2005) ("In order to prevail on a theory of strict liability, the plaintiff must rely on expert testimony when the subject presented is so distinctly related to some science, profession, business or occupation as to be beyond the ken of the average layman.") (citation and quotation marks omitted) (applying District of Columbia law), aff'd in pertinent part, 228 F. Appx. 246 (3d Cir. 2007); Webster v. Pacesetter, Inc., 259 F. Supp.2d 27, 34 (D.D.C. 2003) ("even if they could identify a defect, [plaintiffs] have failed to proffer evidence from an expert who can testify to a reasonable degree of certainty that the defect more likely than not caused the injuries").

First Nations

"The Navajo Nation Supreme Court has recognized the need for expert testimony where a layperson is not qualified to provide a reliable analysis." Harvey v. United States, 685 F.3d 939, 955 (10th Cir. 2012) (applying Navajo law). "Diagnosis of an individual requires professional expertise; when such a diagnosis is used outside the context of its professional use it introduces the risks of mischaracterizations, inaccuracy and potential prejudice and bias." Baldwin v. Chinle Family Court, 2008 WL 5444666 (Navajo Oct. 30, 2008).


Florida "[t]oxic tort cases . . . are won or lost on the strength of the scientific evidence presented to prove causation." Rink v. Cheminova, Inc., 400 F.3d 1286, 1297 (11th Cir. 2005) (applying Florida law). Expert testimony is necessary "to establish legal causation where the issue is beyond the common knowledge of laymen." Benitez v. Joseph Trucking, Inc., 68 So.3d 428, 431 (Fla. App. 2011); accord Gouveia v. Phillips, 823 So.2d 215, 227 (Fla. App. 2002) (expert testimony required "when the discrete issue to be decided is not within the abilities of lay jurors"). Likewise, "the adequacy or inadequacy of the warning to inform a physician must, except in the more obvious situations, be proved by expert testimony." Upjohn Co. v. MacMurdo, 562 So.2d 680, 683 (Fla. 1990).

[I]n complex cases where a jury is asked to assess complex medical or scientific issues outside the scope of a layperson's knowledge, an expert's testimony is required. Without expert testimony, the plaintiff's claim fails as a matter of law.

Small v. Amgen, Inc., 723 F. Appx. 722, 726 (11th Cir. 2018) (citations and quotation marks omitted) (applying Florida law). See Chapman v. Procter & Gamble Distributing, LLC, 766 F.3d 1296, 1316 (11th Cir. 2014) (plaintiffs "were required to have Daubert-qualified, general and specific-causation-expert testimony") (emphasis original) (applying Florida law); Kilpatrick v. Breg, Inc., 613 F.3d 1329, 1334 n.4 (11th Cir. 2010) (following McClain, see Alabama) (applying Florida law); Hendrix v. Evenflo Co., 609 F.3d 1183, 1203 (11th Cir. 2010) ("without this [expert] testimony there is no genuine dispute of material fact regarding causation . . . [and] the district court's grant of summary judgment on [plaintiff's] sole remaining claim was appropriate.") (applying Florida law); Guinn v. AstraZeneca Pharmaceuticals LP, 602 F.3d 1245, 1256 (11th Cir. 2010) ("the exclusion of [plaintiffs' expert's] testimony is a basis for granting summary judgment") (applying Florida law); In re Diet Drugs (Phentermine/Fenfluramine/Dexfenfluramine) Products Litigation, 85 F. Appx. 845, 847 (3d Cir. 2004) ("under Florida law [plaintiff] must present expert testimony regarding causation in order to sustain his suit") (applying Florida law); Tonelli v. NCL (Bahamas) Ltd., 2019 WL 935384 (S.D. Fla. Feb. 26, 2019) ("In Florida, cases involving complicated medical questions require expert opinions to establish causation."); In re Abilify (Aripiprazole) Products Liability Litigation, 299 F. Supp.3d 1291, 1306 (N.D. Fla. 2018) ("To prevail in a pharmaceutical products liability case, a plaintiff must establish both general and specific causation through reliable expert testimony."); Bryant v. C. R. Bard, Inc., 2017 WL 2350228, at *3 (S.D.W. Va. May 30, 2017) (with expert testimony stricken, plaintiff "has not produced any evidence to show medical causation") (applying Florida law); Olmo v. Davol, Inc., 2017 WL 1367231, at *6-7 (S.D. Fla. April 10, 2017) (summary judgment on causation granted in medical device case after plaintiff's experts excluded), aff'd, 710 F. Appx. 861 (11th Cir. 2018); Marshick v. Johnson & Johnson, 2015 WL 9266955, at *3 (M.D. Fla. Dec. 11, 2015) ("A plaintiff must prove general and specific causation by expert testimony."); McCasland v. Pro Guard Coatings, Inc., 2018 WL 5786164, at *3 (M.D. Fla. Nov. 5, 2018) (plaintiff "must present expert testimony linking [the product] to his medical condition to meet this burden"); Payne v. C.R. Bard, Inc., 7, 2014 WL 1887297, at *2 (M.D. Fla. May 12, 2014) ("Expert testimony is generally necessary to prove that a complex product like a medical device is defective."), aff'd, 606 F. Appx. 940 (11th Cir. 2015); Jacob v. Korean Air Lines Co., 2014 WL 1584444, at *6 (S.D. Fla. March 20, 2014) ("Although causation is an issue generally left to a jury, medical causation falls beyond the scope of a layperson’s knowledge and requires competent medical testimony."); Faile v. Dillard's Inc., 2011 WL 13192673, at *2 (N.D. Fla. Nov. 7, 2011) ("plaintiffs must introduce expert testimony to establish medical causation in Florida"), aff'd, 480 F. Appx. 951 (11th Cir. 2012); In re Trasylol Products Liability Litigation, 2011 WL 7109297, at *10 (S.D. Fla. April 27, 2011) ("Plaintiff must, but cannot, establish causation with competent expert testimony in this complex medical case.); Savage v. Danek Medical, Inc., 31 F. Supp.2d 980, 983 (M.D.Fla.1999) ("A defect must be proven by expert testimony"); Baker v. Danek Medical, 35 F. Supp.2d 875, 880 (N.D. Fla. 1998) ("An invitation to the jury to join in speculation is not sufficient medical causation testimony to defeat a summary judgment challenge.").


Georgia law mandates expert testimony "where the existence of a causal link between the defendant's conduct and the plaintiff's injury cannot be determined from common knowledge and experience and instead requires the assistance of experts with specialized medical knowledge." Cowart v. Widener, 697 S.E.2d 779, 784 (Ga. 2010). "[E]ven in simple negligence cases, plaintiffs must come forward with expert evidence . . . where 'medical questions' relating to causation are involved." Id. "[T]oxic tort" cases are a another "example." Id. at 785. "Causation is an essential element of a toxic tort case," and proof of causation in such cases "generally requires reliable expert testimony." Butler v. Union Carbide Corp., 712 S.E.2d 537, 544 (Ga. App. 2011) (footnote omitted). Thus, Georgia "[t]oxic tort cases . . . are won or lost on the strength of the scientific evidence presented to prove causation." Rider v. Sandoz Pharmaceuticals Corp., 295 F.3d 1194, 1197 (11th Cir. 2002). See Barko Response Team, Inc. v. Sudduth, 795 S.E.2d 198, 201-02 (Ga. App. 2016) (reversible error to deny summary judgment where plaintiff submitted no expert evidence in toxic mold case); Seymour Electrical & Air Conditioning Service v. Statom, 710 S.E.2d 874, 877-78 (Ga. App. 2011) (reversible error to deny summary judgment where plaintiff submitted no expert evidence in carbon monoxide poisoning case); Allstate Insurance Co. v. Sutton, 658 S.E.2d 909, 915 (Ga. App. 2008) (summary judgment affirmed in toxic mold case where plaintiff had no expert medical testimony) (punctuation and footnotes omitted).

Product liability claims fall into the same category.

That [the product] can and did cause systemic disease in [plaintiff] is not a natural inference that a juror could make through human experience. Thus, medical expert testimony was essential to prove causation in this case.

Allison v. McGhan Medical Corp., 184 F.3d 1300, 1320 (11th Cir. 1999) (applying Georgia law). See Thurmond v. Bayer Healthcare Pharmaceuticals, Inc., 649 F. Appx. 1003, 1006, n.1 (11th Cir. 2016) ("medical expert testimony is essential in products liability actions when the theory of causation is not a natural inference that a juror could make through human experience") (applying Georgia law); Wilson v. Taser International, Inc., 303 F. Appx. 708, 715 (11th Cir. 2008) (applying Georgia law) ("[i]n product liability cases, proof of causation generally requires reliable expert testimony"); O'Shea v. Zimmer Biomet Holdings, 342 F. Supp.3d 1354, 1364 (N.D. Ga. 2018) (design defect plaintiff "must produce evidence from an expert who . . . opine[s] that the risk inherent in the [product] design outweigh the utility or benefit derived from the product"); Roper v. Kawasaki Heavy Industries, Ltd., 2015 WL 11236553, at *20 (N.D. Ga. June 29, 2015) ("expert testimony is necessary to prove causation if the causal connection between the defective product and the plaintiff's injuries is not a natural inference that a juror could make through human experience"); Wheeler v. Novartis Pharmaceuticals Corp., 944 F. Supp.2d 1344, 1352 (S.D. Ga. 2013) ("In products liability cases, proof of causation generally requires reliable expert testimony."); Brown v. Roche Laboratories, Inc., 2013 WL 2457950, at *8 (N.D. Ga. June 6, 2013) ("[e]xpert testimony is . . . essential to establish causation in this case"), aff'd, 567 F. Appx. 860 (11th Cir. 2014); Parker v. Brush Wellman, Inc., 2010 WL 3730924, at *8 (N.D. Ga. Sept. 17, 2010) ("Plaintiffs' lack of expert testimony is fatal to the causation element of their failure to warn claim"), aff'd, 445 F. Appx. 231 (11th Cir. 2011); Jack v. Glaxo Wellcome, Inc., 239 F. Supp.2d 1308, 1321 (N.D. Ga. 2002) (entering summary judgment after plaintiffs' experts excluded in prescription medical product case); Wheat v. Sofamor, S.N.C., 46 F. Supp.2d 1351, 1361-62 (N.D. Ga. 1999) (same); Smith v. Ortho Pharmaceutical Corp., 770 F. Supp. 1561, 1565 (N.D. Ga. 1991) ("Scientific testimony by expert witnesses on the issue of causation plays an increasingly vital role in [Georgia] products liability litigation.").


Expert testimony in Hawai'i is required where "lay jurors are ill prepared to evaluate complicated technical data for the purpose of determining . . . whether there is a causal relationship between the violation of a duty and an injury to the patient." Exotics Hawaii-Kona, Inc. v. E.I. Du Pont De Nemours & Co., 172 P.3d 1021, 1044 (Haw. 2007) (quoting Bernard v. Char, 903 P.2d 676, 682 (Haw. App.), aff'd, 903 P.2d 667 (Haw. 1995)). In medical causation cases, "[e]xpert medical testimony . . . was required to establish this essential element [causation] of the plaintiff's case." Devine v. Queen's Medical Center, 574 P.2d 1352, 1353 (Haw. 1978). Where a plaintiff "sustained a 'sophisticated injury,' . . . a reasonable jury would need expert medical testimony to determine whether and to what extent any alleged negligence by Defendants contributed to his" injuries. Barbee v. Queen's Medical Center, 194 P.3d 1098, 1123 (Haw. App. 2008).

Thus, "the plaintiff is generally required to provide expert testimony to establish an element of their negligence case." Baker v. Gaspar, 2019 WL 984271, at *6 (D. Haw. Feb. 28, 2019). "[B]ecause Plaintiffs-Appellants' symptoms were medically complex, and . . . beyond the familiarity of the ordinary juror, the jury would have been incompetent to determine the issue of causation. Consequently, expert testimony was essential to enabling the jury to determine causation." Kim-Alaniz v. Executive Center AOAO, 2013 WL 1943181, at *4 (Haw. App. May 10, 2013).

The same is true of product liability. See Haake v. Safeway, 819 F. Supp.2d 1132, 1137 (D. Haw. 2011) ("These are not facts that are subject to common knowledge − Plaintiff needs medical evidence to substantiate these allegations."); Windward Aviation, Inc. v. Rolls-Royce Corp., 2011 WL 2670180, at *21 (D. Haw. July 6, 2011) ("res ipsa loquitur is inapplicable to the complex technical causation issues in this case, for which Plaintiffs have offered no expert testimony in opposition").


Expert opinion is mandatory in Idaho litigation where "the causative factors are not ordinarily within the knowledge or experience of laymen composing the jury." Easterling v. Kendall, 367 P.3d 1214, 1226 (Idaho 2016). "[M]atters [that] are scientific or far removed from the usual and ordinary experience of the average person . . . require expert knowledge." Kolln v. Saint Luke's Regional Medical Center, 940 P.2d 1142, 1149 (Idaho 1997). "[A] lay person cannot arrive at a decision as to causation without the benefit of an expert." Id. at 1228.

[W]here the subject matter regarding the cause of disease, injury, or death of a person is wholly scientific or so far removed from the usual and ordinary experience of the average person that expert knowledge is essential to the formation of an intelligent opinion, only an expert can competently give opinion evidence as to the cause of death, disease or physical condition.

Holdaway v. Broulim's Supermarket, 349 P.3d 1197, 1203 (2015) (citation and quotation marks omitted). A "permanent . . . condition as it exists months or years after the [incident] requires expert testimony to establish causation." Dodge-Farrar v. American Cleaning Services Co., 54 P.3d 954, 959 (Idaho App. 2002).

Thus, "[w]hether or not the [drug] taken by [plaintiff] was a cause of his [condition] is a matter of science that is far removed from the usual and ordinary experience of the average person." Swallow v. Emergency Medicine of Idaho, P.A., 67 P.3d 68, 77 (Idaho 2003). Similarly,"in a toxic tort case . . . the issue of causation is framed by the expert opinions of scientists and treating physicians." Earl v. Cryovac, 772 P.2d 725, 728 (Idaho App. 1989). See McGiboney v. CCA Western Properties, Inc., 2016 WL 843253, at *8 (D. Idaho March 1, 2016) ("complex questions of medical causation require expert testimony"); Sabo v. Fiskars Brands, Inc., 2014 WL 4365319, at *16 (D. Idaho Sept. 2, 2014) ("If the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation.") (citation and quotation marks omitted).


Illinois law holds:

Without question, the human body is complex. In most cases, the connection between the parts of the body and past and current injuries is a subject that is beyond the ken of the average layperson. Because of this complexity, we do not believe that, in normal circumstances, a lay juror can effectively or accurately assess the relationship between a prior injury and a current injury without expert assistance.

Peach v. McGovern, ___ N.E.3d ___, 2019 WL 324608, at *5 (Ill. Jan. 25, 2019) (quoting Voykin v. Estate of DeBoer, 733 N.E.2d 1275, 1280 (Ill. 2000)). Thus, "a plaintiff in a personal injury case must present the testimony of a medical expert to establish causation if the relationship between the claimed injury and the event in question requires special knowledge and training to establish." Brown v. Baker, 672 N.E.2d 69, 71 (Ill. App. 1996). "[L]ay views about the origins of these medically complex problems do not suffice." Joyce v. J.C. Penney Corp., 389 F. Appx. 529, 531 (7th Cir. 2010) (applying Illinois law).

Numerous Illinois decisions have followed this rule in product liability and toxic tort cases.

[P]roduct liability cases are analogous to those involving medical malpractice: Both types of cases involve specialized knowledge that bear directly on the standard of care in the community. . . . [E]xpert opinion usually is required to aid the jury in determining that the pertinent standard of care has been breached.

Baltus v. Weaver Division, 557 N.E.2d 580, 589 (Ill. App. 1990). See Clark v. River Metals Recycling, LLC, 929 F.3d 434, 441 (7th Cir. 2019) ("under Illinois law, [plaintiff] needed expert testimony to pin down exactly why the machine was designed in a defective way") (applying Illinois law); Show v. Ford Motor Co., 659 F.3d 584, 585 (7th Cir. 2011) ("expert testimony is vital in design-defect suits when aspects of a product's design or operation are outside the scope of lay knowledge") (applying Illinois law); Korte v. Exxonmobil Coal USA, Inc., 164 F. Appx. 553, 556 (7th Cir. 2006) ("Expert testimony is needed to establish causation in cases alleging an adverse health effect when the medical effects of exposure to the toxin are not within the ken of the ordinary person.") (applying Illinois law); Fuesting v. Zimmer, Inc., 421 F.3d 528, 537 (7th Cir. 2005) ("In the absence of such [expert] evidence, [plaintiff] cannot establish the requisite elements of his claim."), vacated in part on other grounds, 448 F.3d 936 (7th Cir. 2006) (remedy) (applying Illinois law); Wintz v. Northrop Corp., 110 F.3d 508, 515 (7th Cir. 1997) ("Under Illinois law, to serve as [evidence of] the proximate cause of the plaintiff's injury, an expert must be able to testify with a reasonable degree of medical certainty that proximate cause existed.") (applying Illinois law); Henry v. Panasonic Factory Automation Co., 917 N.E.2d 1086, 1091 (Ill. App. 2009) ("plaintiffs cannot establish a breach of the standard of care in this case without expert testimony"); Kane v. Motorola, Inc., 779 N.E.2d 302, 310 (Ill. App. 2002) ("plaintiffs . . . must come forward with scientific evidence regarding causation to preclude the entry of summary judgment"); Northern Trust Co. v. Upjohn Co., 572 N.E.2d 1030, 1036 (Ill. App. 1991) ("expert testimony shall be necessary . . . in a case, such as the one at bar, where a drug manufacturer's liability for a prescription drug is based upon its failure to provide adequate warnings"); In re Depakote, 2017 WL 5483607, at *2 (S.D. Ill. Nov. 15, 2017) ("Expert testimony is necessary to establish proximate causation in cases where a drug manufacturer has failed to provide adequate warnings."); In re Trasylol Products Liability Litigation, 2010 WL 8354662, at *18 (S.D. Fla. Nov. 23, 2010) ("Under Illinois law, where special medical knowledge is required, Plaintiff must present expert medical testimony to establish causation.") (applying Illinois law); Lewis v. PDV America, Inc., 532 F. Supp.2d 1006, 1010-11 (N. D. Ill 2008) (lack of expert causation testimony fatal to plaintiff's case and warrants summary judgment); Wroble v. Lockformer Co., 2006 WL 695254, at *1 (N.D. Ill. March 17, 2006) ("a plaintiff must establish proximate cause in a personal injury action through the admissible testimony of an expert witness"); Muller v. Synthes Corp., 2002 WL 460827, at *6 (N.D. Ill. March 26, 2002) (issue of "the design parameters of a medical implant . . . is one that goes beyond the knowledge that the average lay person reasonably could be expected to possess. Accordingly, competent proof on this issue requires expert testimony.").


Under Indiana law, "expert testimony is required where the question involves medical factors beyond the common knowledge of the layman." Willis v. Westerfield, 839 N.E.2d 1179, 1188 (Ind. 2006). "Indiana law makes clear that "questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters." Higgins v. Koch Development Corp., 794 F.3d 697, 703 (7th Cir. 2015) (quoting Armstrong v. Cerestar USA, Inc., 775 N.E.2d 360, 366 (Ind. App. 2002)) (applying Indiana law).

[W]hen there is no obvious origin to an injury and it has multiple potential etiologies, expert testimony is necessary to establish causation. . . . Without an expert, a plaintiff in such a complex case would be free . . . to prove his allegations relying on the logical fallacy "post hoc ergo propter hoc". . . . [W]e conclude that a causation expert is required in this case.

Id., 794 F.3d at 703 (citations and quotation marks omitted).

Thus, where "the question of the causal connection . . . is a complicated medical question . . ., testimony of an expert witness on the issue is necessary." Daub v. Daub, 629 N.E.2d 873, 877 (Ind. App. 1994). See Timm v. Goodyear Dunlop Tires North America, Ltd., ___ F.3d ___, 2019 WL 3559049, at *3 (7th Cir. Aug. 6, 2019) ("Indiana law required expert testimony here because distinguishing expected from enhanced injuries was an inquiry beyond the understanding of lay jurors") (applying Indiana law); C.W. v. Textron, Inc., 807 F.3d 827, 838 (7th Cir. 2015) ("With no experts to prove causation − be it general or specific − the appellants cannot prove their toxic-tort case under Indiana law.") (applying Indiana law); Piltch v. Ford Motor Co., 778 F.3d 628, 634 (7th Cir. 2015) (plaintiffs "cannot establish the existence of a defect without expert testimony") (applying Indiana law); Ervin v. Johnson & Johnson, Inc., 492 F.3d 901, 905 (7th Cir. 2007) ("In the absence of any other expert evidence supporting [plaintiff's] causation theory, the district court properly granted summary judgment."). See Armstrong v. Cerestar USA, Inc., 775 N.E.2d 360, 366 (Ind. App. 2002) ("questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters") (quoting Hannan v. Pest Control Services, 734 N.E.2d 674, 679 (Ind. App. 2000)).

The same is true in prescription medical product cases. "[W]hen the issue involves the complex internal medicine question of what caused a person's symptoms when a drug is involved, that is a matter requiring expert opinion to connect the dots." Allen v. Hook-SupeRx, LLC, 2015 WL 1757086, at *3 (N.D. Ind. April 17, 2015).

Under Indiana law questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters. When there is no obvious origin to an injury and it has multiple potential etiologies, expert testimony is necessary to establish causation.

Robinson v. Davol, Inc., 913 F.3d 690, 695 (7th Cir. 2019) (citations and quotation marks omitted) (applying Indiana law).

A mere temporal relationship between [Plaintiff's] ingestion of [a drug] and his subsequent injury cannot form the basis for a reasonable finding of causation. . . . Any finding of the fact of causation based solely on facts within the understanding of lay jurors would be bald speculation. Therefore, this matter presents a situation where expert testimony is not only helpful but absolutely necessary. When the issue of proximate cause is not within the understanding of lay persons, testimony of an expert witness on the issue is necessary. Questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters.

Porter v. Whitehall Laboratory, Inc., 791 F. Supp. 1335, 1341-42 (S.D. Ind. 1992) (citations and quotation marks omitted), aff'd, 9 F.3d 607, 612 (7th Cir. 1993) ("[w]e agree with the district court that expert testimony is necessary"). See Dalton v. Teva North America, 891 F.3d 687, 692 (7th Cir. 2018) ("the issue of causation in [plaintiff's] case is not obvious . . . therefore . . . [plaintiff] could not prove her tort claims without expert testimony") (applying Indiana law); Bowersock v. Davol, Inc., 236 F. Supp.3d 1074, 1089 (S.D. Ind. 2017) (summary judgment granted on causation in medical device case after all plaintiff's experts excluded), aff'd, 913 F.3d 690 (7th Cir. 2019); Tucker v. SmithKline Beecham Corp., 701 F. Supp.2d 1040, 1047 (S.D. Ind. 2010) ("Causation is a required element of each of the plaintiff's claims, and, in pharmaceutical cases, expert testimony is required to prove a causal connection between the drug and its alleged effects."); Minisan v. Danek Medical, Inc., 79 F. Supp.2d 970, 975 (N.D. Ind. 1999) ("[p]roof of legal causation in a medical device case must be by expert testimony").


Iowa law establishes that "medical causation . . . is essentially within the domain of expert testimony." Dunlavey v. Economy Fire & Casualty Co., 526 N.W.2d 845, 853 (Iowa 1995). "[H]ighly technical questions of diagnoses and causation which lie beyond the understanding of a layperson require introduction of expert testimony." Donovan v. State, 445 N.W.2d 763, 766 (Iowa 1989). "[M]edical testimony regarding whether an accident caused an injury is not within the knowledge and experience of ordinary layperson." Yates v. Iowa West Racing Ass'n, 721 N.W.2d 762, 774 (Iowa 2006). "[U]nder Iowa law, due to its complex and scientific nature, medical causation almost always requires expert testimony." Vanderberg v. Petco Animal Supplies Stores, Inc., 906 F.3d 698, 707 (8th Cir. 2018) (citation and quotation marks omitted) (applying Iowa law). "[I]n toxic tort cases, 'expert medical and toxicological testimony is unquestionably required to assist the jury' in determining general and specific causation." Kinseth v. Weil-McLain, 913 N.W.2d 55, 69 (Iowa 2018) (quoting Ranes v. Adams Laboratories, Inc., 778 N.W.2d 677, 688 (Iowa 2010)).

The same rule applies in product liability litigation. "In proving both types [general and specific] of causation, expert medical and toxicological testimony is unquestionably required to assist the jury." Junk v. Terminix International Co., 628 F.3d 439, 450 (8th Cir. 2010) (following Ranes) (applying Iowa law). "In cases involving complicated technical and scientific issues expert testimony is required to submit the issue of a product defect under Iowa law." Iowa Great Lakes Sanitary District v. Travelers Casualty & Surety Co., 913 F.3d 760, 763 (8th Cir. 2019) (citation and quotation marks omitted) (applying Iowa law). An "expert witness testimony opining that [the product] was a likely cause of [the injury is] a crucial element in products liability claims." Doe v. Baxter Healthcare Corp., 178 F. Supp.2d 1003, 1017 (S.D. Iowa 2001), aff'd, 380 F.3d 399 (8th Cir. 2004). "Any decision which pertains to the design of the [medical] device involves engineering, metallurgical and medical principles beyond common knowledge and experience." Benedict v. Zimmer, Inc., 405 F. Supp.2d 1026, 1033 (N.D. Iowa 2005). Questions concerning alternative designs "cannot be fully understood by the average juror without some expert assistance." Id. (citation omitted). Similarly, "to show the device was defective because of inadequate instructions or warnings requires expert testimony." Id. Likewise:

the element of causation . . . requires the presentation of expert evidence. The court concludes the [plaintiffs] must present some expert testimony to prove the complex medical device caused [the] injuries. Causation in this case is a complex medical issue that is beyond common knowledge and experience.

Id. at 1033-34 (citations omitted). See James v. Swiss Valley AG Service, 449 N.W.2d 886, 890 (Iowa App. 1989) ("when technical issues are involved (issues beyond common knowledge and experience) in a products liability or a products-related case, expert testimony is required to generate a jury issue") (citation omitted); Rock v. Smith, 985 F. Supp.2d 1066, 1072 (S.D. Iowa 2013) ("Establishing liability for failure to instruct or warn also requires a plaintiff to establish that the lack of instructions or warnings caused the plaintiff harm.") (citation omitted); Neilson v. Whirlpool Corp., 2012 WL 13018693, at *9 (S.D. Iowa Jan. 3, 2012) ("this products liability action contains issues that are beyond the understanding of the average juror and, therefore, expert testimony is required"); Korte v. Mead Johnson & Co., 824 F. Supp.2d 877, 887 (S.D. Iowa 2010) ("Plaintiffs must use the testimony of medical experts to prove medical causation"); Cummings v. Deere & Co., 589 F. Supp.2d 1108, 1118 (S.D. Iowa 2008) ("the present action involves complicated technical and scientific issues such that expert testimony is required to submit the issue of a product defect to a jury under Iowa law") (footnote omitted); Housley v. Orteck International, Inc., 488 F. Supp.2d 819, 829 (S.D. Iowa 2007) ("The design, manufacture, use, and installation of [the product] is a matter largely outside the experiences of the average juror," therefore "expert testimony is required").


"[T]he well-established test" in Kansas "for determining whether expert testimony is required is whether the subject matter is too complex to fall within the common knowledge of the jury and is beyond the capability of a lay person to decide." Williamson v. Amrani, 152 P.3d 60, 72 (Kan. 2007) (superseded by statute on other grounds). "Expert testimony is necessary where normal experience and qualifications of lay persons serving as jurors does not permit them to draw proper conclusions from the facts and circumstances of the case." Pope v. Ransdell, 833 P.2d 965, 973 (Kan. 1992). Accord Hare v. Wendler, 949 P.2d 1141, 1148 (Kan. 1997) (quoted in Williamson).

The expert requirement has been repeatedly applied in Kansas product liability cases. See Ralston v. Smith & Nephew Richards, Inc., 275 F.3d 965, 974 (10th Cir. 2001) ("[w]ithout the expert testimony . . ., we can discern no material issue of fact with regard to the adequacy of the warnings provided by [the medical device manufacturer]") (applying Kansas law); Robison Farms, Inc. v. ADM Alliance Nutrition, Inc., 2007 WL 2875132, at *19 (D. Kan. Sept. 29, 2007) (where "the facts involve such technical complexities that they exceed the experience and understanding of the average layman . . . without the aid of expert testimony, a reasonable trier of fact could not determine the cause of the harm") (citation, footnote, and quotation marks omitted); Vanderwerf v. SmithKlineBeecham Corp., 529 F. Supp.2d 1294, 1306 (D. Kan. 2008) ("plaintiffs cannot meet their burden of proving medical causation without expert testimony that [the drug] can cause [plaintiff's injury]"); Miller v. Pfizer, Inc., 196 F. Supp.2d 1095, 1125 (D. Kan. 2002) ("Because plaintiffs have no scientific evidence of general causation, their claim of failure to warn must fail as a matter of law."), aff'd, 356 F.3d 1326 (10th Cir. 2004); Smith v. Pfizer Inc., 2001 WL 968369, at *12 (D. Kan. Aug. 14, 2001) ("plaintiff cannot establish general causation, inadequate testing, or inadequate warning because she has no expert through whom to present evidence that a causal relationship or an association exists").


In Kentucky courtrooms, "[i]t is an accepted principle that in most medical negligence cases, proof of causation requires the testimony of an expert witness because the nature of the inquiry is such that jurors are not competent to draw their own conclusions from the evidence without the aid of such expert testimony." Baylis v. Lourdes Hospital, Inc., 805 S.W.2d 122, 124 (Ky. 1991) (citations and footnote omitted). "[T]he human body is perhaps the most complex system known to humankind, so . . . this is exactly why our legal system requires reliable expert proof on issues such as medical causation." Kingery v. Sumitomo Electric Wiring, 481 S.W.3d 492, 499 (Ky. 2015). Thus, "[e]xperts are often required in complex cases in which a jury will not understand, through common knowledge or experience, the intricacies involved in the negligence claim." Caniff v. CSX Transportation, Inc., 438 S.W.3d 368, 374 (Ky. 2014).

Likewise, "expert testimony is required in a products liability case . . . when the subject presented is so distinctly related to an area that is so far removed from the grasp of the average lay person." Stevens v. Keller Ladders, 1 F. Appx. 452, 458 (6th Cir. 2001) (applying Kentucky law).

As a general rule, expert witnesses are generally necessary, indeed essential, in products liability cases, as they are in medical malpractice actions, to prove such matters as a product defect and proximate causation, unless of course the nature of the defect and resultant injuries are so obvious as to fall within the general knowledge of the ordinary person.

Thomas v. Manchester Tank & Equipment Corp., 2005 WL 3673118, at *1 (W.D. Ky. May 13, 2005) (citation and quotation marks omitted).

[E]xpert testimony is necessary to support the element of causation in a negligence action when the common knowledge or experience of lay persons cannot recognize or infer a causal connection between the alleged negligence and the injury. Courts have held that personal injury cases arising out of exposure to drugs involve complex questions of medical causation beyond the understanding of a lay person, and these require expert testimony on causation issues.

Hans v. Matrixx Initiatives, Inc., 2007 WL 2668594, at *3 (W.D. Ky. Sept. 6, 2007) (citations omitted). See Hill v. Express Tan, Inc., 2019 WL 1757534, at *3 (W.D. Ky. April 19, 2019) ("Without expert testimony on any defect related to the tanning bed, the jury would be left to speculate.") (citation and quotation marks omitted); Sturgeon v. Johnson & Johnson, 2017 WL 4080686, at *2 (E.D. Ky. Sept. 14, 2017) (summary judgment appropriate against expert-less plaintiff because "[t]he nature of any defect in the [medical device] is not something that falls within the general knowledge of ordinary people"); Wells v. Wal-Mart Stores Inc., 2016 WL 1453912, at *1 (E.D. Ky. April 13, 2016) ("Expert witnesses are 'generally necessary' in a Kentucky products liability case to prove the presence of a defect."); Earle v. United States, 2016 WL 8814363, at *6 (Mag. E.D. Ky. Feb. 8, 2016) ("Laypeople certainly are not competent, based on common, everyday experience, to judge relative injury causation or delay effect as to a highly complex area of the body."), adopted, 2016 WL 1417811, at *5 (E.D. Ky. April 11, 2016); Hinken v. Sears Roebuck & Co., 2015 WL 165027, at *4 (E.D. Ky. Jan. 13, 2015) (following Thomas and Watson; granting summary judgment); Trent v. Ford Motor Co., 2 F. Supp.3d 1022, 1027 (W.D. Ky. 2014) (plaintiff's "design defect claim turns on specialized knowledge that cannot be determined intelligently from testimony on the basis of ordinary knowledge gained in the ordinary affairs of life.") (citation and quotation marks omitted); Fimbres v. Garlock Equipment Co., 2014 WL 2612513, at *8 (W.D. Ky. June 11, 2014) ("Without the benefit of expert testimony on this issue, Plaintiff cannot meet her burden of producing evidence of the inadequacy of [defendant's] warnings."); Burgett v. Troy-Bilt LLC, 970 F. Supp.2d 676, 683 (E.D. Ky. 2013) (plaintiffs' "attempt to establish causation would crumble for another reason: they need an expert witness"), aff'd, 579 F. Appx. 372 (6th Cir. 2014); Adams v. Cooper Industries, Inc., 2012 WL 2339741, at *1 (E.D. Ky. June 19, 2012) ("Both elements of causation require scientific assessments that must be established through expert testimony."); Jeffrey v. Taylor, 2012 WL 694030, at *5 (W.D. Ky. March 1, 2012) ("the complicated nature of the issues of medical causation and damages require expert testimony and not merely Plaintiff's lay opinion"); Dailey v. Hoffman/New Yorker, Inc., 2011 WL 5598908, at *3 (E.D. Ky. Nov. 17, 2011) (the product "is a technical piece of equipment and expert testimony is required not only to explain the various possible explanations for the accident, including any design and manufacturing defects, but also to opine about the probable cause of the accident"); Freytes v. Wal-Mart Stores East, LP, 2011 WL 2119383, at *4 (E.D. Ky. May 26, 2011) ("expert testimony establishing a connection between the [product] and [plaintiff's] injuries is likely necessary"; plaintiff "simply asks the jury to speculate and surmise too much"); May v. Ford Motor Co., 2010 WL 5391605, at *2 (E.D. Ky. Dec. 22, 2010) (following Thomas; granting summary judgment); Watson v. Ford Motor Co., 2009 WL 5064316, *3 (E.D .Ky. Dec. 15, 2009) ("Expert witnesses are generally necessary, indeed essential, in products liability cases, as they are in medical malpractice actions, to prove such matters as a product defect and proximate causation."); Snyder v. American Honda Motor Co., 2009 WL 2342733, at *7 (E.D. Ky. July 28, 2009) ("Kentucky law requires Plaintiffs to present expert testimony demonstrating that Defendants' product was defective because the subject matter falls outside the general knowledge of the ordinary person"); Honaker v. Innova, Inc., 2007 WL 1217744, at *2 (W.D. Ky. April 23, 2007) ("Expert testimony is almost always needed to meet the plaintiff’s burden in a products liability case.").


For once, Louisiana law is not peculiar, holding that "only a physician or other qualified expert is capable of judging what [medical] risk exists and the likelihood of occurrence." Snider v. Louisiana Medical Mutual Insurance Co., 130 So.3d 922, 930 (La. 2013).

[W]e find the plaintiff was required to produce evidence from a medical expert to establish a breach of the standard of care, as well as causation. . . . Here, the plaintiff was required to present medical evidence to establish the defendant's actions fell below the standard of care and caused her injuries. Without this evidence, the plaintiff has, in our view, failed to show that she will be able to carry her burden of proof at trial. . . . We conclude the plaintiff . . . was required to produce expert medical evidence sufficient to establish that she will be able to satisfy her evidentiary burden of proof at trial.

Schultz v. Guoth, 57 So.3d 1002, 1009-10 (La. 2011) (citations omitted). "[O]ur long standing jurisprudence has held, because of the complex medical and factual issues involved, a plaintiff will likely fail to sustain his burden of proving his claim . . . without medical experts." Khammash v. Clark, 145 So.3d 246, 259 (La. 2014) (citations and quotation marks omitted). See Madere v. Collins, 241 So.3d 1143, 1149 (La. App. 2018) ("complex surgical and medical actions . . . require expert evidence of the applicable standard of care and expert testimony regarding negligence and causation").

The same is true in product liability and toxic tort actions. ("When a conclusion regarding medical causation is not one within common knowledge, expert medical testimony is required in a tort action." Johnson v. E.I. DuPont de Nemours & Co., 7 So.3d 734, 740 (La. App. 2009). "[T]o conclude that a different [design] or a different warning would have" changed the outcome in a product liability action,

therefore raises questions that are of sufficient complexity to be beyond the expertise of the average judge and juror and that common sense does not make obvious. Accordingly, [plaintiffs] were required to provide the jury with expert testimony related to causation.

Stewart v. Capital Safety USA, 867 F.3d 517, 521-22 (5th Cir. 2017) (applying Louisiana law). See Boudreaux v. Bollinger Shipyard, 197 So.3d 761, 775 (La. App. 2016) ("expert medical testimony is required when the conclusion regarding medical causation is one that is not within common knowledge"); Bourgeois v. Garrard Chevrolet, Inc., 811 So.2d 962, 967 (La. App. 2002) ("Without expert testimony, the plaintiff cannot carry his burden of proof that the [product] was defective in design or that an alternative design would have prevented the plaintiff's injuries"); Hutchinson v. Shah, 648 So.2d 451, 452 (La. App. 1994) ("When the conclusion regarding medical causation is not one within common knowledge, expert medical testimony is required."); Winstead v. Georgia Gulf Corp., 77 F. Appx. 267, 271 (5th Cir. 2003) (plaintiff "was required to present expert testimony because the cause of [a] chemical release is beyond the understanding of an untrained lay person") (applying Louisiana law); Barber v. Spinal Elements, 2019 WL 3554200, at *4 (E.D. La. Aug. 5, 2019) ("courts consistently require expert testimony in products liability cases, when the product or feature in question is complex, and a layman may not readily grasp the implications"); Talbot v. Electric Insurance Co., 2018 WL 6274314, at *3 (M.D. La. Nov. 30, 2018) ("as a matter of law, non-expert testimony by a fact witness is insufficient to establish medical causation"); Patton v. Boston Scientific Corp., 2018 WL 4760846, at *2 (W.D. La. Oct. 2, 2018) ("in tort actions involving complex medical devices and concepts, medical causation cannot be established without the aid of expert medical testimony"); Williams v. Janssen Pharmaceuticals, 2016 WL 6127526, at *2 (W.D. La. Oct. 20, 2016) ("A plaintiff must have expert medical testimony to prove causation in a product liability claim involving prescription medications."); Hooks v. Nationwide Housing Systems, LLC, 2016 WL 3667134, at *13 (E.D. La. July 11, 2016) ("In a toxic tort case, the plaintiff must present admissible expert testimony to establish general causation as well as specific causation. Konrick v. Exxon Mobil Corp., 2016 WL 430404, at *2 (E.D. La. Feb. 4, 2016) ("In a toxic tort suit, the plaintiff must present admissible expert testimony to establish general causation and specific causation"); Underwood v. General Motors LLC, 2015 WL 5475610, at *3 (M.D. La. Sept. 17, 2015) ("it is not possible for a jury to determine a product to be defective . . . without expert testimony"), aff'd, 642 F. Appx. 468 (5th Cir. 2016); Burst v. Shell Oil Co., 2014 WL 3893304, at *2 (E.D. La. Aug. 8, 2014) ("expert medical testimony is required to resolve the issue of general causation"); Demouchet v. General Nutrition Corp., 2014 WL 1652518, at *4 (W.D. La. April 24, 2014) ("In cases such as this, involving complex issues of medical causation that are beyond the realm of knowledge and experience of the ordinary juror, expert testimony must be presented by the plaintiff to prove specific causation."); Sadler v. International Paper Co., 2014 WL 1217954, at *3 (W.D. La. March 24, 2014) ("A plaintiff in a toxic tort case must establish medical causation through expert testimony."); Pratt v. Landings at Barksdale, 2013 WL 5376021, at *3 (W.D. La. Sept. 24, 2013) ("In a toxic tort suit, the plaintiff must present admissible expert testimony to establish general causation as well as specific causation.") (citation and quotation marks omitted); Rhodes v. Bayer Healthcare Pharmaceuticals, Inc., 2013 WL 1282450, at *2 (W.D. La. March 28, 2013) ("lack of an expert to establish causation is fatal to Plaintiffs' claims"); Autery v. SmithKline Beecham Corp., 2011 WL 1812793, at *6 (Mag. W.D. La. April 12, 2011) ("courts routinely dismiss product liability cases in which expert testimony on causation is lacking"), adopted, 2011 WL 1828343 (W.D. La. May 12, 2011), aff'd, 496 F. Appx. 388 (5th Cir. 2012); Horton v. Wyeth Pharmaceuticals, 2010 WL 11607305, at *3 (W.D. La. May 27, 2010) ("summary judgment is appropriate on the independent ground that [plaintiffs] have failed to identify an expert witness or submit an expert report. Such failure is fatal to their prescription drug product liability action, as expert medical testimony is required"); Smith v. Glaxosmithkline Corp., 2008 WL 4938426, at *2 (E.D. La. Nov. 17, 2008) ("Plaintiffs can only establish the required elements of causation between [the drug] and [decedent's] death through expert testimony"); Waters v. Bayer Corp., 2006 WL 725820, at *2 (W.D. La. March 22, 2006) ("In a case such as this, involving complex medical issues not commonly known to the average person, the courts have held that expert medical testimony must be offered to prove causation."); Kemp v. Metabolife International, Inc., 2004 WL 2095618, at *3 (E.D. La. Sept. 13, 2004) ("proof of actual causation requires medical testimony").


Under Maine law, "[a]llowing a jury to infer causation on complex medical facts without the aid of expert testimony on the subject . . . stretches the jury's role beyond its capacity." Merriam v. Wanger, 757 A.2d 778, 782 (Me. 2000). Where a case "concerns such technical and involved medical procedure that it rules out any possibility of understanding on the part of a layman as to its medical nature" it falls within "the general rule [requiring] expert medical testimony." Cyr v. Giesen, 108 A.2d 316, 318 (Me. 1954).

[T]he identification of a cause for serious medical conditions . . . − let alone prospective injuries that have not yet developed − is neither a lay exercise" nor "a matter within common, non-expert understanding. Rather, the causal relationship . . . draws on sophisticated science beyond the ken of the average juror. Accordingly, a jury may not infer causation on complex medical facts without the aid of expert testimony.

Darney v. Dragon Products Co., LLC, 640 F. Supp.2d 117, 123 (D. Me. 2009) (citations, quotation marks, and footnote omitted). See Samaan v. St. Joseph Hospital, 670 F.3d 21, 38 (1st. Cir. 2012) ("Given the complex medical question that underlies the issue of causation in this instance, expert testimony was essential.") (applying Maine law); Rollins v. Wentworth, 2013 WL 3781504, at *7 (D. Me. 2013) ("with a plaintiff having as complex a medical history as [plaintiff], it would be necessary to produce expert testimony from a qualified medical expert"); Kalis v. Strang, 2005 WL 2715239, at *4 (Me. Super. May 9, 2005) ("because plaintiff never named an expert, he will be unable to link his symptoms to the [accident]").


The rule in maritime cases is that "[e]xpert testimony is required whenever proof of an element of a claim, such as the duty of care or causation, calls for information that is outside an ordinary person's common knowledge." Rhodes v. Energy Marine LLC, 2016 WL 6700973, at *3 (D. Ariz. Nov. 15, 2016) (appling maritime law).

Where, however, the nexus between the injury and the alleged cause would not be obvious to the lay juror, expert evidence is often required to establish the causal connection between the accident and some item of physical or mental injury. In a case such as this, where an injury has multiple potential etiologies, expert testimony is necessary to establish causation, even in view of plaintiff’s reduced burden to prove causation.

Wills v. Amerada Hess Corp., 379 F.3d 32, 46 (2d Cir. 2004) (citations and quotation marks omitted) (Sotomayor, J.) (appling maritime law). See Seaman v. Seacor Marine L.L.C., 326 F. Appx. 721, 729 (5th Cir. 2009) (in toxic exposure case, with expert testimony excluded, plaintiff "lacks competent summary judgment evidence that would create a genuine fact issue regarding . . . causation") (applying maritime law); Gauthreaux v. United States, 694 F. Supp.2d 460, 465 (E.D. Va. 2009) ("in a products liability action, proof of causation must ordinarily be supported by expert testimony because of the complexity of the causation facts") (applying maritime law); Holman v. Applied Drilling Technology, Inc., 2007 WL 1577660, at *3 (S.D. Tex. May 31, 2007) ("Expert testimony is particularly necessary in chemical-exposure cases, in which medically complex diseases and causal ambiguities compound the need for expert testimony.") (citation and quotation marks omitted) (applying maritime law).

This article is presented for informational purposes only and is not intended to constitute legal advice.

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