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The Defense Line: A Publication From The Maryland Defense Counsel, Inc.

Expert Testimony in Maryland — Maintaining the Frye-Reed Standard: Unanimity Not Required for Exclusion, as the Existence of a Genuine Controversy is Enough

Angela W. RussellPeter W. ChinAngela W. Russell and Peter W. Chin
In a unanimous decision, the Court of Special Appeals reversed a trial court’s determination that an expert’s theories and methodologies used to establish a causal link between mold exposure and human health effects were admissible, finding instead that under the Frye-Reed analysis there was genuine controversy in the scientific community regarding the expert’s diagnosis methods and theories. Montgomery Mutual Insurance Company. v. Chesson, 206 Md. App. 569, 51 A.3d 18 (2012) (“Chesson III”). In doing so, the Court of Special Appeals reiterated the doctrine followed in Maryland that was first adopted in Reed v. State: “if a new scientific technique’s validity is in controversy in the relevant scientific community, or if it is generally regarded as an experimental technique, then expert testimony based upon its validity cannot be admitted into evidence.” 283 Md. 374, 381, 391 A.2d 364, 368 (1978). This case marks the continued departure from the more lenient Daubert standard that is followed in federal courts and in the vast majority of state courts.

Expert testimony challenged: Factual and procedural background of Montgomery Mut. Ins. Co. v. Chesson, 206 Md. App. 569 (2012) (Chesson III)

In late 2002, after a group of employees of the Baltimore Washington Conference of the United Methodist Church (“BWCUMC”) complained of a malodor emanating from the walls of the church, two types of mold were discovered. The employees filed Workers’ Compensation claims, alleging that they had sustained an accidental injury or occupational disease known as “sick building syndrome” as a result of mold exposure. Workers’ Compensation claims by two of the employees were denied, and they appealed to the Circuit Court of Howard County.

Prior to trial, the trial court denied BWCUMC’s motion in limineseeking to exclude the testimony of Ritchie Shoemaker, M.D., the physician who had examined each employee and concluded that sick building syndrome had caused their injuries, and held that a Frye-Reed hearing was unnecessary. BWCUMC had argued that Dr. Shoemaker’s theories and methodologies for diagnosis regarding a causal connection between mold exposure and certain human health effects had not been generally accepted within the relevant scientific community. The trial court reasoned that Dr. Shoemaker's testimony was not the proper subject of a Frye-Reed hearing, but was a medical opinion, which was not subject to Frye-Reed, and thus was admissible.

The trial proceeded and the jury returned verdicts in favor of each plaintiff, finding a causal relationship between mold exposure and certain illnesses claimed by plaintiffs. The Court of Special Appeals upheld the Circuit Court's ruling, holding that the lower court correctly declined to conduct a Frye-Reed hearing, specifically noting that “expert opinions concerning the cause or origin of an individual's condition are not subject to Frye-Reed analysis.” Montgomery Mut. Ins. Co. v. Chesson, 170 Md. App. 551, 569, 907 A.2d 873, 884 (2006) (“Chesson I”).

The Court of Appeals reversed, holding that a Frye-Reed hearing should have been held “to determine whether the medical community generally accepts the theory that mold exposure causes the illnesses that [the employees] claimed to have suffered, and the propriety of the tests Dr. Shoemaker employed to reach his medical conclusions.”Montgomery Mut. Ins. Co. v. Chesson, 399 Md. 314, 328, 923 A.2d 939, 947 (2007) (“Chesson II”) (emphasis added). The Court of Appeals explained that Dr. Shoemaker's medical tests were not so widely accepted as to be subject to judicial notice of reliability and thus, his causation theories and diagnostic testing methodologies were indeed subject to Frye-Reed analysis. 329, 923 A.2d at 947.

On remand, the trial court conducted a Frye-Reed hearing where Dr. Shoemaker explained the development of his theories and methodologies. He described the various studies, diagnostic approaches, and treatments that he has explored — including the use of differential diagnosis — regarding illnesses associated with exposure to toxins. Dr. Shoemaker described the specific tests and methods he has developed to diagnose and treat patients with illnesses that he specifically attributes to exposure to water-damaged buildings, including a two-stage test involving establishing a patient’s exposure and then observing certain test results that, according to Dr. Shoemaker, would confirm a causal link. The result of his process was to illustrate inflammation which, according to Dr. Shoemaker, is a biomarker for illnesses related to exposure to water-damaged buildings.

BWCUMC’s expert, Hung Cheung, M.D., in turn presented an approach which considered four different criteria to evaluate patients with environmental exposure to mold. He explained that because there are different types of exposure, he would have to determine which one caused a patient's symptoms.

Dr. Cheung acknowledged that Dr. Shoemaker could impart a diagnosis using a differential diagnosis method, but that the issue of causationhas “nothing to do with differential diagnosis.” The differential diagnosis, according to Dr. Cheung, merely revealed the health effects being suffered. More importantly, Dr. Cheung further suggested the proposition that exposure to toxic mold by inhalation in water-damaged buildings causes certain health effects is not supported by the medical literature. Accordingly, Dr. Cheung opined that“"Dr. Shoemaker's methodology, treatment, and opinion regarding causation are controversial and not generally accepted in the scientific community" — that is, they do not satisfy the Frye-Reed standard for admissibility. This case was then considered by the Court of Special Appeals of Maryland.

What the Court of Special Appeals said in Chesson III

The issues on appeal to the Court of Special Appeals, the second time, were whether Dr. Shoemaker’s theories and methodologies were reliable and acceptable to establish general and specific causation and whether his differential diagnosis method was generally accepted in the medical community. The Court found that although under the Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786 (1993), standard — which eschews the requirement of a method’s general acceptance in the scientific community — it would have determined that Dr. Shoemaker’s theories regarding causation were reliable, under Maryland’s Frye-Reed standard, however, Dr. Shoemaker’s theories and methodologies were not generally accepted in the medical community, and thus, it determined that the Circuit Court erred in admitting his testimony.

The Court of Special Appeals reviewed de novo the experts’ theories and methodologies.1 It looked at the trial court’s findings of fact and opinion where they accepted Dr. Shoemaker’s diagnostic method as reliable to establish general and specific causation, specifically whether exposure to mold caused the employees’ neurocognitive and musculoskeletal problems. The Court of Special Appeals noted that at the Frye-Reed hearing, Dr. Shoemaker pointed to two articles authored by other scientists that were published in scientific publications that supported his theory regarding “sick building syndrome.” He also observed that two articles that he authored on the subject had been published in scientific journals as well.

Conversely, Dr. Cheung, BWCUMC’s expert, presented an approach that he claimed could be used to determine what may be the cause of a patient’s illness. He further observed that a differential diagnosis, such as the one described by Dr. Shoemaker, could be used to expose the health effects being experienced by a patient, but that “the scientific literature does not support the notion that exposure to toxic mold by inhalation in water damaged buildings causes certain human health effects.” Chesson III, 206 Md. App. at 576, 51 A.3d at 23. The Court of Special Appeals also noted the myriad scholarly articles reflecting the notion that “demonstrate[s] that there is a genuine controversy within the scientific community with regard to whether exposure to water damaged buildings causes the human health effects Dr. Shoemaker suggests are caused by exposure to water damaged buildings.” Id. at 607, 51 A.3d at 41.

Ultimately, the Court of Special Appeals, in reversing the trial court’s decision to admit Dr. Shoemaker’s testimony held that “because there are sources that support and oppose Dr. Shoemaker's theories and methodologies, and at least one that recognizes the relevant scientific field is undecided, we must conclude that Dr. Shoemaker's theories and methodologies with regard to exposure to water damaged buildings, and the human health effects suffered by appellees, are not generally accepted in the relevant scientific community.” Chesson III, 206 Md. App. at 607, 51 A.3d at 41. The court reiterated the notion that its decision hinged on the distinction between the application of the Daubert standard and of the Frye-Reed standard. Namely, that Daubert — the standard adopted in federal courts and in the vast majority of states — does away with the latter’s requirement that an expert’s causation theories be generally accepted in the scientific or medical community. Id. The court has remained consistent in its reluctance to adopt this Daubert standard. This matter is, once again, before the Court of Appeals.

What comes next — standards for expert testimony

If this decision is not reversed on appeal, the Court of Special Appeals has established its position on the admissibility of scientific theories and methods regarding causation of injury under Maryland’s Frye-Reed standard for admitting expert witness testimony. The rule of law derived from this case is that while unanimity is not required to establish general acceptance of propounded scientific methods and tests — the existence of medical articles within the relevant scientific community that express contradictory perspectives on the validity of a method to determination causation can establish that a genuine controversy exists. Accordingly, a court may deny the admission of an expert’s opinion when the scientific articles supporting the expert’s position are controverted by scientific articles that oppose the conclusions of the former ones.

The result of this case firmly re-establishes that the passing of Maryland Rule of Evidence 5-702 did not abrogate the expert testimony admissibility standard established in Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), and adopted in Maryland in Reed. More likely, this case more clearly marked the distinction between what is required to satisfy the Frye-Reed and Daubert standards. To reiterate, the Court of Appeals, in Reed, articulated its “general acceptance rule” as interpreted from Frye:

On occasion, the validity and reliability of a scientific technique may be so broadly and generally accepted in the scientific community that a trial court may take judicial notice of its reliability. . . Similarly, a trial court might take judicial notice of the invalidity or unreliability of procedures widely recognized in the scientific community as bogus or experimental. However, if the reliability of a particular technique cannot be judicially noticed, it is necessary that the reliability be demonstrated before testimony based on the technique can be introduced into evidence. Although this demonstration will normally include testimony by witnesses, a court can and should also take notice of law journal articles, articles from reliable sources that appear in scientific journals, and other publications which bear on the degree of acceptance by recognized experts that a particular process has achieved.


That is to say, before a scientific opinion will be received as evidence attrial, the basis of that opinion must be shown to be generally accepted as reliable within the expert's particular scientific field. Thus, according to the Frye standard, if a new scientific technique's validity is in controversy in the relevant scientific community, or if it is generally regarded as an experimental technique, then expert testimony based upon its validity cannot be admitted into evidence.

Reed, 283 Md. at 380—81, 391 A.2d at 367—68 (citing Frye, 293 F. at 1014).

In Chesson III, the Court of Special Appeals noted that where Dr. Shoemaker presented scientific literature to support his position that exposure to mold in homes caused certain health effects, it equally acknowledged Dr. Cheung’s cited articles that debunked the association. Notably, the Court acknowledged further that Dr. Cheung proposed “in the alternative, that more research was necessary.” Chesson III, 206 Md. App. at 603, 51 A.3d at 39. The Court here seems to have reiterated that even in close calls, where the testimony or evidence offered to challenge an expert’s testimony is not fully conclusive on an issue, but rather may need “more research,” a court should not admit the expert’s testimony.

The decision in Chesson III should not be a sea change in the well-established law of evidence in Maryland as set forth in seminal cases such as Reed. Nevertheless, while it cannot be predicted how a trial court would exercise its discretion in a given case, in response to scientific or medical evidence proffered by plaintiffs, defendants can be expected to seek to admit rebuttal evidence that, at a minimum, will establish the notion that “more research [i]s necessary,” if not effectively debunk the proffered theories. Trial courts may view Chesson III as a bright-line rule to deny admission of an expert’s testimony based on the mere existence of scientific or medical literature stating an opposing proposition. The Court of Appeals will have the last word on the subject, however, given that it granted certiorari to review the Court of Special Appeals’ decision, and will hear the appeal on June 11, 2013.

Angela Russell is the regional managing partner of Wilson Elser’s Baltimore office.. She has significant trial experience and has tried cases across the state of Maryland., in the District of Columbia and Minnesota. Her practice encompasses the defense of professional liability matters, including medical malpractice and legal malpractice actions as well as claims against agents, brokers and other professionals. Angela also regularly handles catastrophic general casualty matters.

Peter W. Chin is an associate in the Baltimore office of Wilson Elser Moskowitz Edelman & Dicker LLP. His practice focuses on commercial and civil litigation with a concentration on medical malpractice, products liability and personal injury.


1The Circuit Court issued its findings of fact fourteen months later, and its opinion on the matter of admissibility six months after that, noting in the latter “that the question of admissibility of expert medical testimony to prove general or specific causation appears to be a case of first impression in Maryland.” Id. at 588, 51 A.3d at 30 (internal quotation marks omitted).

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