Opinion ID: 149189
Heading Depth: 3
Heading Rank: 1

Heading: Legal Standards for Admitting Scientific Evidence of Causation

Text: Hendrix seeks to admit expert testimony that the traumatic brain injury G.P. sustained in the accident caused his ASD. Because this is a diversity case, we apply Florida's substantive law regarding a plaintiff's burden of proof on causation. McLeod v. Am. Motors Corp., 723 F.2d 830, 832 (11th Cir.1984). Under Florida law, Hendrix may recover damages upon showing that the trauma was a substantial factor causing G.P.'s ASD. Gross v. Lyons, 763 So.2d 276, 279 (Fla.2000); Hart v. Stern, 824 So.2d 927, 929-30 (Fla. 5th DCA 2002). A purported cause is a substantial factor if it operates in combination with another cause, such as the negligent act of another or the plaintiff's pre-existing physical condition, to cause an injury. Gross, 763 So.2d at 279; Hart, 824 So.2d at 929-30. Although the standards for finding causation are governed by Florida law, we apply federal law to determine whether the expert testimony proffered to prove causation is sufficiently reliable to submit it to the jury. Flury v. Daimler Chrysler Corp., 427 F.3d 939, 944 (11th Cir.2005) (noting that in diversity cases, the Federal Rules of Evidence govern the admissibility of evidence in federal court). The Federal Rules of Evidence provide: If scientific ... knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case. Fed.R.Evid. 702. Unlike an ordinary witness... an expert is permitted wide latitude to offer opinions, including those that are not based on firsthand knowledge or observation. Daubert, 509 U.S. at 592, 113 S.Ct. at 2796. [T]his relaxation of the usual requirement of firsthand knowledge... is premised on an assumption that the expert's opinion will have a reliable basis in the knowledge and experience of his discipline. Id. A trial court assessing the reliability of an expert's evidence must therefore perform a gatekeeping function by conducting a preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue. Id. at 592-93, 113 S.Ct. at 2796. We have offered district courts the following general guidance in determining whether to admit scientific evidence under Daubert: Given time, information, and resources, courts may only admit the state of science as it is. Courts are cautioned not to admit speculation, conjecture, or inference that cannot be supported by sound scientific principles. The courtroom is not the place for scientific guesswork, even of the inspired sort. Law lags science; it does not lead it. Rider v. Sandoz Pharms. Corp., 295 F.3d 1194, 1202 (11th Cir.2002) (quoting Rosen v. Ciba-Geigy Corp., 78 F.3d 316, 319 (7th Cir.1996)). This circuit requires trial courts acting as gatekeepers to engage in a rigorous three-part inquiry assessing whether: (1) the expert is qualified to testify competently regarding the matters he intends to address; (2) the methodology by which the expert reaches his conclusions is sufficiently reliable as determined by the sort of inquiry mandated in Daubert ; and (3) the testimony assists the trier of fact, through the application of scientific, technical, or specialized expertise, to understand the evidence or to determine a fact in issue. United States v. Frazier, 387 F.3d 1244, 1260. The proponent of the expert testimony bears the burden of showing, by a preponderance of the evidence, that the testimony satisfies each prong. See Boca Raton Cmty. Hosp., Inc. v. Tenet Health Care, 582 F.3d 1227, 1232 (11th Cir.2009). Here, the parties raise no issues regarding the first and third prongs. Therefore, our analysis will focus on whether the district court abused its discretion in excluding the expert testimony of Dr. Hoffman and Dr. Suhrbier upon finding that the testimony was not sufficiently reliable under Daubert. The Daubert Court described several factors trial judges may use to assess the reliability of proffered scientific testimony, including: (1) whether the theory or technique can be (and has been) tested, (2) whether the theory or technique has been subjected to peer review and publication, (3) in the case of a particular scientific technique, ... the known or potential rate of error, and (4) whether the theory or technique is generally accepted by the relevant scientific community. Daubert, 509 U.S. at 592-94, 113 S.Ct. at 2796-97; see also Rink, 400 F.3d at 1292 (discussing these factors in the context of assessing an expert's particular scientific technique). This list, however, is not exhaustive, and district courts have substantial discretion in deciding how to test an expert's reliability. Rink, 400 F.3d at 1292. In addition, the Supreme Court has noted that, in the context of this analysis, conclusions and methodology are not entirely distinct from one another. General Elec. Co. v. Joiner, 522 U.S. 136, 146, 118 S.Ct. 512, 519, 139 L.Ed.2d 508 (1997). Although experts commonly extrapolate from existing data ... nothing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert. Id. Rather, the trial court is free to conclude that there is simply too great an analytical gap between the data and the opinion proffered. Id. Hendrix's experts rely primarily on the differential etiology method [5] to link G.P.'s traumatic brain injury to his ASD diagnosis. Differential etiology is a medical process of elimination whereby the possible causes of a condition are considered and ruled out one-by-one, leaving only one cause remaining. See supra n. 5. Hendrix argues that the experts' opinions were reliable because differential etiology is a well-recognized scientific method that has been accepted by many courts as a valid basis for expert testimony. See, e.g., Best v. Lowe's Home Centers, Inc., 563 F.3d 171, 178-84 (6th Cir.2009); McClain, 401 F.3d at 1252-53; Clausen v. M/V New Carissa, 339 F.3d 1049, 1057 (9th Cir. 2003). We have previously noted that, when applied under circumstances that ensure reliability, the differential etiology method can provide a valid basis for medical causation opinions. See McClain, 401 F.3d at 1252. Here, the reliability of the method must be judged by considering the reasonableness of applying the differential etiology approach to the facts of this case and the validity of the experts' particular method of analyzing the data and drawing conclusions therefrom. See Kumho Tire, 526 U.S. at 153-54, 119 S.Ct. at 1177 ([T]he specific issue before the court was not the reasonableness in general of a tire expert's use of a visual and tactile inspection to determine whether overdeflection had caused the tire's tread to separate from its steel-belted carcass. Rather, it was the reasonableness of using such an approach, along with Carlson's particular method of analyzing the data thereby obtained, to draw a conclusion regarding the particular matter to which the expert testimony was directly relevant. ) (emphasis in original); see also Quiet Tech. DC-8 v. Hurel-Dubois UK Ltd., 326 F.3d 1333, 1343 (11th Cir.2003). A reliable differential etiology analysis is performed in two steps. First, the expert must compile a comprehensive list of hypotheses that might explain the set of salient clinical findings under consideration.... The issue at this point in the process is which of the competing causes are generally capable of causing the patient's symptoms. McClain, 401 F.3d at 1253 (quoting Clausen v. M/V NEW CARISSA, 339 F.3d 1049, 1057-58 (9th Cir. 2003)). Second, the expert must eliminate all causes but one. See McCullock v. H.B. Fuller Co., 61 F.3d 1038, 1044 (2d Cir. 1995). With regard to the first step, the district court must ensure that, for each possible cause the expert rules in at the first stage of the analysis, the expert's opinion on general causation is derived from scientifically valid methodology. Hollander v. Sandoz Pharm. Corp., 289 F.3d 1193, 1211 (10th Cir.2002) (quoting Siharath v. Sandoz Pharms. Corp., 131 F.Supp.2d 1347, 1362-63 (N.D.Ga.2001)). This is because a fundamental assumption underlying [differential etiology] is that the final, suspected `cause' ... must actually be capable of causing the injury. McClain, 401 F.3d at 1253. Thus, the experts' purported use of the differential etiology method will not overcome a fundamental failure to lay the scientific groundwork for the theory that traumatic brain injury can, in general, cause autism. See McClain, 401 F.3d at 1252 (This approach, however, will not usually overcome the fundamental failure of laying a scientific groundwork for the general toxicity of the drug and that it can cause the harm a plaintiff suffered.). Some specific principles arise in the context of establishing general causation in cases dealing with medical injuries. In McClain, we distinguished cases in which the medical community generally recognizes that a certain chemical can cause the injury the plaintiff alleges from those in which the medical community has not reached such a consensus. 401 F.3d at 1239. [6] We stated that in the second category of cases, the district court must apply the Daubert analysis not only to the expert's methodology for figuring out whether the chemical caused the plaintiff's specific injury, but also to the question of whether the drug or chemical can, in general, cause the harm plaintiff alleges. Id. Thus, the district court must assess the reliability of the expert's opinion on general, as well as specific, causation. Id. Hendrix does not contend that the medical community generally recognizes traumatic brain injury as a cause of autism. Therefore, the district court was correct to apply the Daubert analysis to the question of whether traumatic brain injury can, in general, cause autism. [7] We afford the district court substantial discretion to decide how to test the reliability of the general causation evidence presented by Dr. Hoffman and Dr. Suhrbier. Rink, 400 F.3d at 1292. In reviewing the district court's reliability determination, we note that we have previously identified some of the scientifically valid methods for establishing general causation. For instance, we will admit expert opinions pursuant to Daubert that are supported by epidemiological studies, [8] provided the expert explains how the findings of those studies may be reliably connected to the facts of the particular case. Rider, 295 F.3d at 1198 (noting that, although they are not mandatory, epidemiological studies may be powerful evidence of causation); see also, Norris v. Baxter Healthcare Corp., 397 F.3d 878, 882 (10th Cir.2005) ([E]pidemiology is the best evidence of general causation in a toxic tort case.). An expert's opinion will likely also survive Daubert if the expert describes the physiological process, derived by the scientific method, by which a particular cause leads to the development of a given disease or syndrome. McClain, 401 F.3d at 1253 (The underlying predicates of any cause-and-effect medical testimony are that medical science understands the physiological process by which a particular disease or syndrome develops and knows what factors cause the process to occur.) (quoting Black v. Food Lion, Inc., 171 F.3d 308, 314 (5th Cir.1999)); see also Daubert, 509 U.S. at 590, 113 S.Ct. at 2795 (noting that in order to qualify as scientific knowledge for the purposes of Fed. R.Evid. 702, an inference or assertion must be derived by the scientific method). Courts have also identified other methods that, when used alone, are unable to provide scientifically valid proof of general causation. For instance, in McClain, we explained that the  post hoc ergo propter hoc fallacy assumes causality from temporal sequence.... It is called a fallacy because it makes an assumption based on the false inference that a temporal relationship proves a causal relationship. McClain, 401 F.3d at 1243. Thus, a mere temporal relationship between an event and a patient's disease or symptoms does not allow an expert to place that event on a list of possible causes of the disease or symptoms. Case studies and clinical experience, used alone and not merely to bolster other evidence, are also insufficient to show general causation. See Rider, 295 F.3d at 1199 (Although a court may rely on anecdotal evidence such as case reports... courts must consider that case reports are merely accounts of medical events. They reflect only reported data, not scientific methodology.) (internal citation omitted); see also Norris, 397 F.3d at 887 (We cannot allow the jury to speculate based on an expert's opinion which relies only on clinical experience in the absence of showing a consistent, statistically significant association between breast implants and systemic disease.). In the second step of the differential etiology analysis, the expert must eliminate all causes but one. See McCullock, 61 F.3d at 1044. While the first step focuses on general causation, in the second step the expert applies the facts of the patient's case to the list created in the first step in order to form an opinion about the actual cause of the patient's symptoms, i.e., to determine specific causation. In Clausen, the Ninth Circuit stated that an expert must provide reasons for rejecting alternative hypotheses using scientific methods and procedures and the elimination of those hypotheses must be founded on more than subjective beliefs or unsupported speculation. 339 F.3d at 1058 (internal quotation omitted). Thus, [a] district court is justified in excluding evidence if an expert `utterly fails ... to offer an explanation for why the proffered alternative cause' was ruled out. Id. (quoting Cooper v. Smith & Nephew, Inc., 259 F.3d 194, 202 (4th Cir.2001)). With these principles in mind, we now review the district court's determination that the experts' testimony in this case was unreliable under Daubert.