EvidenceProf Blog

Editor: Colin Miller
Univ. of South Carolina School of Law

Monday, October 31, 2016

Daubert's Werewolf and the Concept of "Fit" With Expert Evidence

In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), the United States Supreme Court replaced the old  Frye test for determining the admissibility of expert evidence with the new Daubert, pursuant to which judges serve as gatekeepers and determine the reliability/admissibility of expert evidence by looking at factors such as

(1) whether the theory or technique in question can be and has been tested; (2) whether it has been subjected to peer review and publication; (3) its known or potential error rate; (4) the existence and maintenance of standards controlling its operation; and (5) whether it has attracted widespread acceptance within a relevant scientific community.

A less well known portion of the Court's Daubert opinion deals with the idea of "fit" as it relates to expert evidence. To establish this point, Justice Blackmon uses a werewolf analogy that some have since dubbed Daubert's werewolf.


According to Justice Blackmon's majority opinion,

Rule 702 further requires that the evidence or testimony "assist the trier of fact to understand the evidence or to determine a fact in issue." This condition goes primarily to relevance. "Expert testimony which does not relate to any issue in the case is not relevant and, ergo, non-helpful."...The consideration has been aptly described by Judge Becker as one of "fit."..."Fit" is not always obvious, and scientific validity for one purpose is not necessarily scientific validity for other, unrelated purposes....The study of the phases of the moon, for example, may provide valid scientific "knowledge" about whether a certain night was dark, and if darkness is a fact in issue, the knowledge will assist the trier of fact. However (absent creditable grounds supporting such a link), evidence that the moon was full on a certain night will not assist the trier of fact in determining whether an individual was unusually likely to have behaved irrationally on that night. Rule 702's "helpfulness" standard requires a valid scientific connection to the pertinent inquiry as a precondition to admissibility.

This dichotomy makes sense. For instance, there is a classic case in which Abraham Lincoln proved secured a "not guilty" verdict for William "Duff" Armstrong by establishing that Charles Allen's alleged eyewitness identification of Armstrong "[b]y the light of the moon" was impossible given the phase of the moon.* Conversely, an expert's claim that the moon was full on the night of the murder would not be helpful to the jury in determining whether the defendant behaved irrationally on the night of the murder because there is no evidence that werewolves exist or that people's behavior is otherwise impacted by a full moon.

Several authors have expounded upon Justice Blackmon's analogy. According to Joelle Moreno in The Future of Neuroimaged Lie Detection and the Law, 42 Akron L. Rev. 717, 729 (2009),

A more colorful and equally persuasive example is Justice Blackmun's Daubert werewolf. Writing for the Daubert majority, Justice Blackmun explained that valid moon phase studies should be admitted to reveal lighting conditions; but that these same studies should be excluded if they have been proffered to explain the criminal defendant's bizarre behavior. Thus, in the cognitive neuroscience context, research designed to reveal deception that is based on the brain activity of subjects who have been instructed to lie about insignificant events under highly artificial conditions should be excluded unless and until there is adequate empirical evidence demonstrating that this research can reasonably and reliably be applied to the case.

Bobak Razavi, meanwhile, notes in Admissible Expert Testimony and Summary Judgment, 29 J. Legal Med. 307, 315 (2008), that

the Court seems to say that scientific testimony regarding the phases of the moon "fits" the facts of a case if the issue is whether a certain night was dark, whereas such testimony does not "fit" the facts of a case if the issue is whether a person acted like a werewolf on a certain night. This distinction makes good intuitive sense: it effectively laughs out of court an "expert" who believes in werewolves, while admitting the testimony of an expert who has more serious and scientifically valid notions in mind. As such, the issue of "fit" is a useful tool for excluding bad evidence.

As David Crump argues in The Case for Selective Abolition of the Rules of Evidence, 35 Hofstra L. Rev. 585, 634 n.215 (2006),

The Court observed that while information about phases of the moon might "fit" the question of the relative darkness of a certain night, it would not "fit" the question whether an individual "was unusually likely to have behaved irrationally on that night."...But the later conjecture (which might be called the “werewolf inference”) is excludable not because it does not "fit," but because it thoroughly flunks the Court's separate concept of "reliability." If the werewolf inference could be established as a "reliable" scientific principle, then ironically, it probably would "fit," because it predicts an outcome that precisely answers the assumed issue--but this is like asking, "If planets were bigger than stars, how far away would they be?," because the werewolf inference is not "reliable." 

Carlton Bailey adds in Arkansas Adopts a Second Admissibility Test for Novel Scientific Evidence: Do Two Tests Equal One Standard?, 56 Ark. L. Rev. 21 that

A few commentators have opined that "this example has led some lawyers to suggest that Daubert requires the trial judge to conduct a 'werewolf inquiry': Rule 702 requires the court to determine whether the scientific principle has a better relationship to the case than phases of the moon have to inferences about werewolf-like human behavior."

Finally, Ninth Circuit Judge Alex Kozinski pointed out in Brave New World, 30 U.C. Davis L. Rev. 997, 1002-1003 (1997), that

Daubert said the testimony has to "fit." It is not enough that it is scientific. It has to be relevant to something in the case; it has to make a difference. Consider Justice Blackmun's example: He said if you bring in an expert about the phases of the moon, that may well be relevant when you are trying to figure out whether there was enough light. For example, if a particular witness were to testify about seeing a series of events, the phases of the moon might well be relevant to the question of whether he could see what he testified to. However, if you are trying to prove that the defendant was likely to be rabid because the moon was out, Justice Blackmun says the evidence is inadmissible. We realize that people will tell you that when the moon is full, people go berserk. I have seen An American Werewolf in London. We know that people believe this, but it is not scientific. It does not fit with the theory of the case.


*The same could be said about the bare sliver of a moon contradicting Jay Wilds's claim of using moonlight to see snow on the ground on the night of January 13, 1999.




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There wasn't even a bare sliver of the moon to help Jay to see the snow at the time in question: the moon set that day around late afternoon and didn't rise again until 4am'ish. But indeed, once risen, it was in a phase where it was a tiny sliver.

Posted by: Paul | Oct 31, 2016 12:26:06 PM

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