MATRICCIANI, J.
On July 1, 2008, Joan Dixon and her husband, Bernard Dixon, brought suit in the Circuit Court for Baltimore City against corporations involved in the manufacturing and distribution of products containing asbestos, including Ford Motor Company, the Georgia-Pacific Corporation ("GP"), Honeywell International, Inc., and the Union Carbide Corporation ("UCC"). Following Mrs. Dixon's death from pleural mesothelioma, Mr. Dixon pursued her claims as representative of her estate, and the Dixons' four adult daughters joined their father as plaintiffs, who are now appellants.
Prior to trial, appellants settled with GP, Honeywell, and UCC, but Ford's cross-claims against those defendants remained for adjudication as potential joint tortfeasors.
Ford moved in limine for a hearing to challenge appellants' proffered expert on the issue of causation, as well as to exclude the expert's testimony. Trial commenced on April 15, 2010, and the court denied Ford's motions, along with certain objections Ford raised during the expert's testimony.
On April 27, 2010, the jury returned a verdict awarding appellants a total of $15,000,000 in compensatory damages, which the court reduced to $6,065,000 in accordance with the non-economic damages cap of Maryland Code (2006), § 11-108 of the Courts and Judicial Proceedings Article ("CJ"). Ford subsequently filed post-trial motions requesting a new trial and revisions or judgments notwithstanding the verdict ("JNOV") on both its own cross-claims and appellants' direct claims. The court denied Ford's motions for new trial and JNOV, but ruled that the jury's verdict was inconsistent and revised the judgments against Ford and GP to adjust for the latter's contribution as a joint tortfeasor. The court entered its revised judgment in favor of appellants in the collective amount of $3,032,500.00, from which both appellants and Ford filed timely appeals.
The parties' briefs present a total of eight questions between them,
For the reasons that follow, we answer yes and remand the case for a new trial consistent with this opinion.
Joan Dixon died of pleural mesothelioma on February 28, 2009, having initiated a suit against Ford and various other entities involved in the asbestos market, including GP, Honeywell, and UCC. The complaint alleged that Mr. and Mrs. Dixon "participated in home improvement and maintenance projects throughout the 1960s and 1970s during with [sic] they worked with and around Defendants' asbestos products," and that "[t]hroughout the 1950s, 1960s and 1970s, Mrs. Dixon was exposed to asbestos dust created by Mr. Dixon's work with and around asbestos-containing automobiles and asbestos-containing replacement parts for those automobiles including ... brakes[.]" Appellants further alleged that Mrs. Dixon's "exposure to Defendants' asbestos containing products and asbestos containing vehicles and the inhalation of asbestos fibers from the products and vehicles caused her disease and eventual death."
In response to interrogatories, appellants stated that they "believe Joan Dixon may have been exposed to asbestos through her and her husbands' use of and exposure to various building materials, including but not limited to Georgia Pacific pre-mixed drywall joint compound which, upon information and belief, contained Union Carbide Corporation's Calidria brand asbestos." Deposition testimony established that Mrs. Dixon personally sanded joint compound and cleaned up after at least five home construction and renovation projects.
Appellants sought to introduce Dr. Laura Welch as an expert in asbestos epidemiology and proffered her opinion on causation. Ford did not dispute that Dr. Welch was qualified to render expert testimony on the subject of epidemiology, but instead objected to the methods and substance of her causation opinion. The court denied Ford's motion,
Dr. Welch admitted that no epidemiological studies had specifically investigated the risk of mesothelioma among wives of brake mechanics. However, Dr. Welch explained that such a study would be practically impossible; if the rate of disease in a group of workers was two-and-a-half cases per hundred thousand — as in the case of mesothelioma — such a study would require thirty-thousand subjects and twenty years to reach a statistically significant conclusion. Instead, Dr. Welch testified that she formed her opinion from the generally accepted fact that asbestos dust left on a worker's clothing can be transmitted to family members in the home environment.
In its defense, Ford called epidemiologist and risk assessment expert Herman J. Gibb, Ph.D., who testified that none of eighteen epidemiological studies in evidence showed "any evidence that vehicle mechanics have an increased risk of mesothelioma." By contrast, Dr. Gibb testified that epidemiological studies showed that the risk of mesothelioma among construction workers exposed to asbestos dust is up to seven times greater than the risk of mesothelioma among the general population. Dr. Gibb admitted on cross-examination that only three of the studies that Ford relied upon categorically examined "brake mechanics," as opposed to "auto workers" or generic "mechanics."
After the close of evidence, the jury deliberated and returned a verdict against Ford, awarding $5,000,000 to Mrs. Dixon's estate, $4,000,000 to Bernard Dixon, and $1,500,000 to each of the Dixons' four daughters, for a total of $15,000,000. After applying the non-economic damages
Ford argues that the trial court erred when it admitted Dr. Welch's testimony on the issue of causation and supports its argument with three premises. First, Ford contends that Dr. Welch's testimony was inadmissible under the holdings of Reed v. State, 283 Md. 374, 391 A.2d 364 (1978), and Blackwell v. Wyeth, 408 Md. 575, 971 A.2d 235 (2009). Second, Ford argues that Dr. Welch's opinion deserves special scrutiny under Frye-Reed "in the face of epidemiological evidence to the contrary," which Ford introduced in its defense. Third, Ford argues that "Dr. Welch's causation opinions fundamentally are at odds with `the frequency, regularity and proximity' requirements for substantial factor causation" set forth in Eagle-Picher Industries, Inc. v. Balbos, 326 Md. 179, 604 A.2d 445 (1992). In response, appellants argue first that Dr. Welch's testimony was not subject to the Frye-Reed test because it was based upon her specialized knowledge, training, and skill in a relevant field of inquiry. Second, appellants argue that Ford's epidemiological studies are not conclusive. Third, appellants argue that the Balbos standard "is a test of legal causation," and that Dr. Welch's ultimate opinion was admissible because it addressed only "medical or epidemiological causation." For the following reasons, we hold that the trial court abused its discretion under Maryland Rule 5-702 when it admitted Dr. Welch's testimony. See Exxon Mobil Corp. v. Ford, 204 Md.App. 1, 27 n. 20, 40 A.3d 514 (Md.App.2012) (Zarnoch, J. concurring and dissenting) (whereas Frye-Reed determinations are reviewed de novo, Rule 5-702 decisions are reviewed for abuse of discretion).
In Reed, the Court of Appeals adopted the test first articulated in Frye v. United States, 293 F. 1013, 1014 (D.C.Cir.1923), now known in Maryland as the Frye-Reed standard: "[B]efore a scientific opinion will be received as evidence at trial, the basis of that opinion must be shown to be generally accepted as reliable within the expert's particular scientific field." 283 Md. at 381, 391 A.2d 364. In Blackwell v. Wyeth, the Court applied Frye-Reed to a novel theory of causation. Drawing from the Supreme Court's decision in GE v. Joiner, 522 U.S. 136, 146, 118 S.Ct. 512, 139 L.Ed.2d 508 (1997), the Blackwell Court held that where an expert derives an untested hypothesis from generally accepted theories and research methods, the trial court must weigh the "analytical gap" between the established theories and methods on one figurative side, and the expert's opinion on the other. 408 Md. at 605-08, 971 A.2d 235 ("Generally accepted methodology, therefore, must be coupled with generally accepted analysis in order to avoid the pitfalls of an `analytical gap.'").
Despite their perceived differences, the parties in fact agree on the fundamental scientific principles undergirding the expert testimony on both sides. Ford's amici,
The question open to scientific debate is the extent to which various asbestos exposures increase the risk of mesothelioma. Notably, calculations by the United States Environmental Protection Agency indicate that even ambient air levels of asbestos increase one's risk of cancer and mesothelioma.
We therefore have a settled scientific theory of causation, and it is captured by what philosophers of science call "probabilistic causation," a logical model that accounts for the inherent uncertainty in counterfactual truth.
397 U.S. 358, 370, 90 S.Ct. 1068, 25 L.Ed.2d 368 (1970).
Probabilistic causation is, of course, different in kind from the legal burden of proof. The former is a mental model that states causal assertions as continuous conditional probabilities, whereas the latter is a discrete threshold for legal action set at some level of belief in specific causation. In spite of this difference, both doctrines rest on the premise that empirical inquiry can only ever give a certain degree of certainty in an inference of fact from evidence, including conditional and counterfactual assertions of causation.
Despite the parties' (unrecognized) agreement on the science of mesothelioma causation and the conceptual framework that it entails, Ford attacks Dr. Welch's methodology on the grounds that it is not generally accepted. Specifically, Ford argues that Dr. Welch's opinion testimony violated the tenets of Blackwell and Balbos
Like the closely-related concept "proximate cause," the term "substantial contributing factor" goes beyond the logically simple question of whether the defendant's action (or inaction) was a "necessary" or "sufficient" condition of harm to the plaintiff. Both proximity and substantiality describe whether "the defendant's conduct has such an effect in producing the harm as to lead reasonable men to regard it as a cause, using that word in the popular sense, in which there always lurks the idea of responsibility[.]" Restatement (Second) of Torts § 431 (1965). Where the question of causation is probabilistic, "substantiality" and "responsibility" necessarily imply some test of magnitude,
If risk is our measure of causation, and substantiality is a threshold for risk, then it follows — as intimated above — that "substantiality" is essentially a burden of proof. Moreover, we can explicitly derive the probability of causation from the statistical measure known as "relative risk," as did the U.S. Court of Appeals for the Third Circuit in DeLuca v. Merrell Dow Pharmaceuticals, Inc., 911 F.2d 941, 958 (3d Cir.1990), in a holding later adopted by several courts.
Dr. Welch testified that, in her opinion, "every exposure to asbestos is a substantial contributing cause and so brake exposure would be a substantial cause even if [Mrs. Dixon] had other exposures." And while we have no doubt that Dr. Welch is well-qualified to render some opinion as to the likely intensity of Mrs. Dixon's exposure and the likely effect it had on her risk of mesothelioma, Dr. Welch's testimony implied only that both were "more than nothing." For obvious reasons an infinitesimal change in risk cannot suffice to maintain a cause of action in tort. Thus, whatever information Dr. Welch conveyed could not possibly have helped the jurors to weigh the substantiality
Dr. Welch's conclusion that the exposure and risk in this case were "substantial" simply was not a scientific conclusion, and without it her testimony did not provide information for the jury to use in reaching its conclusion as to substantial factor causation. For these reasons and in these circumstances (i.e., where probabilistic causation is the generally accepted scientific theory of causation and scientific expert testimony is required), we join with several other courts in requiring quantitative epidemiological evidence.
Before we conclude our discussion, we address Ford's remaining arguments so as to avoid four possible points of confusion. First, Ford complains that "downward extrapolation" is not a reliable method to establish substantial factor causation, but that argument is only trivially true. As we have seen, "substantiality" is a legal concept and not an objective property testable by the scientific method. The contributions of science end at quantitative estimates of exposure and risk. Thus, it is primarily Dr. Welch's conclusion, and not her methodology, with which we take issue.
Second, we agree with Ford's contention that "case reports" and other anecdotal evidence are not probative of either general or actual causation,
Third, we would not use language so strong to describe Ford's arguments about the "analytical gap" in this case, but Professor Vern R. Walker dispelled similar notions in his comprehensive article "Restoring the Individual Plaintiff to Tort Law by Rejecting `Junk Logic' About Specific Causation," 56 Ala. L.Rev. 381 (2004). In it, Professor Walker explains that any opinion rendered as to the likelihood of actual causation in a specific case must bridge the "analytical gap"
Id. at 384-85.
Thus, it could be said that while epidemiology can provide an accurate estimate of general causation among a population that controls for as many variables as possible, actual causation lies outside the bounds of epidemiological inquiry per se. See Reference Manual on Scientific Evidence at 381. Epidemiology informs an opinion of actual causation by establishing general causation, but the link between the two will always require some degree of untested inference and uncertainty, which brings us to our third point of clarification. It would be folly to require an expert to testify with absolute certainty that a plaintiff was exposed to a specific dose or suffered a specific risk. Dose and risk fall on a spectrum and are not "true or false." As such, any scientific estimate of those values must be expressed as one or more possible intervals and, for each interval, a corresponding confidence that the true value
Practical and statistical limitations may have prevented Dr. Welch from providing any particular estimates of Mrs. Dixon's exposure or relative risk, or from opining with any reasonable certainty that the probability of causation was enough that a reasonable person would consider it substantial. But lack of epidemiological data does not give an expert license to state his or her belief that exposure and risk — however low they may be — are "substantial." While under Rule 5-704 Dr. Welch's testimony was "not objectionable merely because it embraces an ultimate issue to be decided by the trier of fact," the remainder of her opinion lacked any information that would "assist the trier of fact to understand the evidence or to determine a fact in issue" as required by Rule 5-702. Having erroneously gained the court's imprimatur of expert testimony, Dr. Welch's unhelpful opinion was prejudicial to Ford and demands a new trial, either without her opinion on substantiality or else with some quantitative testimony that will help the jury fulfill its charge. We therefore vacate the judgments in favor of appellants and remand the case for a new trial consistent with this opinion.
In addition to the question presented, above, Ford asked:
In addition, Mrs. Dixon was exposed to Georgia Pacific joint compound when she and Mr. Dixon built the family meat store and apartments in 1976. Mrs. Dixon testified that she used Georgia Pacific Ready Mix joint compound to finish the drywall work in the apartments from 1976 to 1977. Mr. Dixon testified that she did the drywall work in the same manner as the work she had previously done, including sanding, cleaning, and doing the laundry. During the relevant time period when Mr. and/or Mrs. Dixon performed home renovation work, Mrs. Dixon did the laundry.
Toxicological Profile for Asbestos at 24 app. F.
All of this is not to say, however, that any and all attempts to establish a burden of proof of causation using relative risk will fail. Decisions can be — and in science or medicine are — premised on the lower limit of the relative risk ratio at a requisite confidence level. The point of this minor discussion is that one cannot apply the usual, singular "preponderance" burden to the probability of causation when the only estimate of that probability is statistical relative risk. Instead, a statistical burden of proof of causation must consist of two interdependent parts: a requisite confidence of some minimum relative risk. As we explain in the body of our discussion, the flaws in Dr. Welch's testimony mean we need not explore this issue any further.
97 Harv.L.Rev. 849, 870 (1984) (footnotes omitted). See also Walker, Preponderance, Probability, and Warranted Factfinding, 62 Brooklyn L.Rev. at 1080-92.
