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‘Cornell’ Ruling on Mold Clarifies ‘Reliability’ Needed from Experts

April 14, 2014 in  News

New York Law Journal 

Our prior Products Liability columns often elaborated well-established New York law on judicial screening or “gatekeeping” of expert testimony.1 The Court of Appeals made it clear in Parker v. Mobil Oil Corp.2 that questions regarding reliability of experts’ testimony required diligent policing by courts. And, now, a new ruling, the Cornell decision, makes the point emphatically. The basic rules seem simple enough. If “novel” scientific evidence is involved, the court applies the Frye “general acceptance” test to determine “whether the accepted techniques, when properly performed, generate results accepted as reliable within the scientific community generally.” If the answer is “no,” the testimony has flunked and must be precluded or excluded. If the answer is “yes,” the proponent of the novel scientific testimony has survived the threshold test but still has to get past the admissibility “gate.” The evidence must meet a second, “foundational reliability” inquiry.

This second admissibility standard applies to all expert testimony, not just “novel” scientific evidence. In Parker, the court said the Frye inquiry is “separate and distinct from the admissibility question applied to all evidence—whether there is a proper foundation—to determine whether the accepted methods were appropriately employed in a particular case.” Parker declared that the focus moves “from the general reliability concerns of Frye to the specific reliability of the procedures followed to generate the evidence proffered and whether they establish a foundation for the reception of evidence at trial.”

In fact, Parker itself was a claim that a gas station attendant’s leukemia was caused by exposure to benzene in gasoline. The court said that no particular “novel” methodology was at issue for which “general acceptance” of the scientific community needed to be determined. Instead, the issue was foundational reliability—”an inquiry…more akin to whether there is an appropriate foundation for the expert’s opinions.” In other words, do the methodologies “lead to a reliable result?” In Parker the court’s reliability-policing led to the conclusion that, although the experts were highly qualified in their respective fields, they “failed to demonstrate that exposure to benzene as a component of gasoline caused [Mr.] Parker’s AML.”

Although the foregoing seems clear, we nevertheless see occasional bursts of departure from these mature principles of reliability. Perhaps, this merely reflects lawyers (and some judges) pushing the envelope. More likely, perhaps, the trend toward “trial by literature” may be a culprit. Prior columns have addressed problems with this phenomenon3 and, for space reasons, we do not revisit it here. Another contribution to uncertainty may be the increasing tendency toward proffering “conduit hearsay.” Thus, an expert may refer to or quote from out-of-court hearsay, for example a technical or scientific article, and this then becomes outright the only or major basis for the expert’s opinion. In effect, the expert becomes a parrot or mouthpiece for what others have said or written, hence a mere “conduit” for the hearsay writing.

Effectively, the out-of-court article is “testifying” but the article’s author is not available for cross-examination. The actual testifier can then deflect pointed questions by saying, in effect, “I don’t know but the author, university or institution named in the article is in my opinion reliable.” Such “conduit hearsay” also can be used unfairly to bolster the testifier’s vulnerable position by suggesting that the renowned creators of the hearsay “agree” with him. The shortcomings of this approach were discussed years ago in my article, “‘Conduit Hearsay’: A Minefield for Lawyers.”4

Just two weeks ago, however, the New York Court of Appeals issued its key decision in Cornell v. 360 W. 51st St. Realty, LLC,5 yet again offering detailed guidance to bench and bar on a variety of expert reliability issues. Although the court’s approach generally tracks Parker, there are additional lessons of note. Further, the court describes the rulings of the courts below in some detail (and with textual emphasis) so the reader can understand in what way the Appellate Division may have gone astray. Ditto for identifying flaws in the rejected expert’s testimony.

Mold Claim

Plaintiff Brenda Cornell was a resident of a Manhattan building which developed mold as a result of demolition and construction work in the basement. Plaintiff became physically ill attributing a variety of ailments to exposure to mold and other harmful substances. She vacated the apartment, surrendered her lease and sued the landlord and other parties seeking $11.8 million in damages plus an additional $10 million in punitive damages. The defendants, in turn, sued the contractor in a third-party action.

The defendant moved for summary judgment specifically seeking dismissal of the complaint to the extent plaintiff alleged mold-induced personal injuries. Defendant urged that Cornell could not prove that mold can cause the type of injuries she alleged (general causation), or that apartment mold caused her specific injuries (specific causation). Defendant also sought preclusion of plaintiff’s experts from testifying on causation. In the alternative, defendant sought a Frye hearing on whether plaintiff’s theory of causation enjoyed “general scientific acceptance.” The defense motion was supported by an affidavit of S. Michael Phillips, a clinical immunologist with more than 30 years of clinical and basic science experience in the fields of internal medicine, allergy and immunology. Dr. Phillips is a Senior Scholar in Clinical Epidemiology at the University of Pennsylvania.

Defendant’s expert opined with reasonable medical certainty that there was “no relationship between the medical problems experienced by Ms. Cornell and exposure to molds.” On “general causation,” Dr. Phillips relied on the position paper of the American Academy of Allergy, Asthma and Immunology (AAAAI) which he referred to as “the current ‘state of the art’ and widely accepted as authoritative.”6 Dr. Phillips said that “[l]ess than 1% of the [Academy’s members … questioned the report.” Further, even assuming general causation, Cornell could not demonstrate “specific causation” for some seven itemized reasons quoted by the court in its opinion.7 One of these was that plaintiff’s complained-of medical problems “are common in the human population regardless of indoor exposure to molds.” Further, molds “have never been shown to cause other physical and psychological problems that Cornell ascribes to indoor mold exposure (e.g., cognitive problems, seizures, depression).”

Plaintiff opposed the motion with an affidavit by Eckhardt Johanning, a doctor of environmental and occupational medicine who specializes in mold-related illness. The expert criticized Dr. Phillips as having “no formal training or professional experience in the pertinent field” as well as the “out of date” or “discredited” publications upon which the latter relied. He, on the other hand, had examined Cornell many times, having been brought in to consult at a very early stage of her condition. According to Dr. Johanning, the illness was “undeniably caused by exposure to an unusual mixture of atypical microbial contaminants.”8

Further, he cited a number of studies saying that various mold byproducts “may” have adverse effects to humans; the “risk” of certain conditions was higher in damp homes; there is “sufficient evidence of associations” of building dampness with the presence of mold and certain conditions; there is “suggestive evidence of associations” with shortness of breath and development of asthma; and the existence of recent studies “support the link” between a damp indoor environment, mold growth and upper airway irritant symptoms. Other reports, government papers or guidelines also referred to “associations,” “risks,” public health “concerns” and “various possible adverse health effects.”9

The motion court in Cornell granted summary judgment to defendant, relying heavily on another mold-illness case (the “Fraser litigation”) in which a 10-day Frye hearing in 2006, with more than 1,000 pages of testimony and introduction of more than 70 scientific articles and books, resulted in preclusion of the plaintiff’s expert for failure to show “general acceptance” by the scientific community of the mold-causation premise. The trial judge in Fraser additionally had ruled that dismissal was required for insufficient foundational reliability of plaintiff’s expert under Parker. In 2008 a divided Appellate Division affirmed in Fraser. Dr. Johanning was the main plaintiff’s expert in that case as well.10

Opinions Unreliable

In Cornell, the Appellate Division reversed (with one justice dissenting) since plaintiff had shown “some support” in existing data, studies and literature and, further, since Dr. Johanning had performed a “differential diagnosis.” The Court of Appeals, however, disagreed. On this record, the expert’s conclusions on general and specific causation were deemed insufficient. The court reiterated its established principles regarding Frye and Parker standards on receiving expert evidence.

Although Frye focuses on principles and methodologies, these are “not entirely distinct from one another.” Even if an expert is using reliable principles and methods and is extrapolating from reliable data, a court may still exclude the expert’s opinion if “there is simply too great an analytical gap between the data and the opinion proffered.” Thus, an opinion connected to existing data “only by the ipse dixit of the expert” may be excluded. The expert’s conclusion, too, has to be reliable. The court reiterated that the precept has sometimes been expressed in terms of the “general foundation inquiry applicable to all evidence.”11

Although Dr. Johanning attacked Dr. Phillips’ qualifications, the latter was “clearly qualified” on the issue presented. Although plaintiff’s expert condemned the AAAAI report as “out of date” and “discredited,” he did not claim it was withdrawn or indicate where its conclusions were ever repudiated by the scientific community. Although Dr. Johanning cited government reports and public health initiatives regarding mold, these were irrelevant since “standards promulgated by regulatory agencies as protective measures are inadequate to demonstrate legal causation.”12 Finally, the studies cited by plaintiff’s expert merely spoke in terms of “risk,” “linkage” and “association”—”not causation.” Indeed, plaintiff’s expert repeatedly equated association with causation. He thereby departed from the generally accepted methodology for evaluating epidemiological evidence as reflected in the Reference Manual on Scientific Evidence.13

Studies that show an “association” between a damp and moldy indoor environment and plaintiff’s medical conditions do not “establish” that the relevant scientific community generally accepts that molds “cause” such adverse health effects. For these reasons, the Appellate Division erred when it ruled that the Frye standard was satisfied in this case based on “some support” in the record. Proof of general causation was thus lacking.

Even “assuming” Cornell’s expert demonstrated general causation, he did not reliably show the necessary specific causation. As Parker explains, an opinion on causation should set forth not only a plaintiff’s exposure to a toxin and that the toxin is capable of causing the particular illness (general causation) but also that plaintiff was “exposed to sufficient levels” of the toxin to cause the illness (specific causation).14 Thus, there must be evidence that plaintiff was exposed to “levels of that agent that is shown to cause the kind of harm that plaintiff claims to have suffered.”15

Here plaintiff’s expert did not identify the specific disease-causing agent other than to vaguely describe it as “an unusual mixture of atypical microbial contaminants.” He made no effort to quantify Cornell’s level of exposure to this “unusual mixture.” Further, the expert’s “differential diagnosis” was unavailing. Such a “rule in,” “rule out” approach “assumes general causation has been proven.” Scientifically valid methodology must be used in any event. The Appellate Division was incorrect when it suggested that performance of a differential diagnosis establishes sufficient exposure to an agent to prove specific causation. Nor did this record supply a proper foundation for the expert’s differential diagnosis. First, many of the medical conditions plaintiff attributes to mold exposure are common in the general population. Second, many of her symptoms may be ascribed to non-mold-related diseases. Further, the expert did not “explain what other possible causes he ruled out or in, much less why he did so.” Although he says he performed diagnostic tests, he did not give any results.16

In closing, the court did observe that the Frye record in the Fraser litigation was completed more than six years ago. Since the scientific consensus at a given point in time may or may not endure the Court of Appeals’ decision does not stand for the proposition that a cause-and-effect relationship based on exposure to mold does not exist. Rather, “Cornell simply did not demonstrate such a relationship on this record.”


Reliability of expert testimony is a critical element of both the Frye “general acceptance” test, applicable to “novel” scientific evidence, and the “foundational reliability” criterion applicable to all scientific evidence. The Parker precedent has been amplified aplenty by the new Cornell ruling. Both should be on litigators’ “must read” lists.

Michael Hoenig is a member of Herzfeld & Rubin.


  1.  See M. Hoenig, “Experts ‘Frye’d’ on Tylenol-Cirrhosis Link,” New York Law Journal, Dec. 12, 2011, p. 3; “Testifying Experts and Scientific Articles: Reliability Concerns,” NYLJ, Sept. 16, 2011, p. 3 (citing prior articles on experts’ use of unreliable hearsay, scientific papers questioning the reliability of biomedical articles, and reporting serious shortcomings even in those that were peer reviewed); “‘Parker,’ ‘Frye’ and Gatekeeping of Experts: an Update,” NYLJ, June 17, 2009, p. 3; “Judicial Gatekeeping: ‘Frye,’ ‘Foundational Reliability,'” NYLJ, Feb. 11, 2008, p. 3; “‘Gatekeeping’ of Experts and Unreliable Literature,” NYLJ, Sept. 12, 2005, p. 3. The articles are also available on LEXIS.
  2.  7 N.Y. 3d 434 (2006).
  3.  See M. Hoenig, “Testifying Experts and Scientific Articles: Reliability Concerns,” NYLJ, Sept. 16, 2011, p. 3; “‘Gatekeeping’ of Experts and Unreliable Literature,” NYLJ, Sept. 12, 2005, p. 3.
  4.  NYLJ, March 13, 2006, p. 3.
  5.  2014 NY Slip Op 02096 (Ct. App. March 27, 2014).
  6.  Cornell, Id. Slip Op, at pp. 4—5.
  7.  Id. Slip Op, at p. 5.
  8.  Id. Slip Op, at p. 6 (Emphasis by court).
  9.  Id. Slip Op, at pp. 6—7.
  10.  Fraser v. 301—52 Townhouse Corp., 57 A.D. 3d 416 (1st Dept. 2008), appeal dismissed, 12 N.Y. 3d 847 (2009).
  11.  Id., Slip Op, at p. 14 (citing Parker and Wesley, 83 N.Y.2d at 422).
  12.  Id., Slip Op, at pp. 15—16 (quoting from Parker, 7 N.Y.3d at 450).
  13.  Id., Slip Op, at p. 16 (citing and quoting the federal courts’ Reference Manual on Scientific Evidence, p. 566 (3d ed. 2011) (“an association does not necessarily mean that there is a cause-—effect relationship”).
  14.  Id., Slip Op, at p. 17 (quoting from Parker).
  15.  Ibid. (quoting from Wright v. Willamette Ind., 91 F.3d 1105, 1107 (8th Cir. 1996)).
  16.  Id., Slip Op, at p. 18.