CrimProf Blog

Editor: Kevin Cole
Univ. of San Diego School of Law

Thursday, September 29, 2011

Shniderman on Polygraph Evidence

Adam B. Shniderman has posted You Can’t Handle the Truth: Lies, Damn Lies, and the Exclusion of Polygraph Evidence (Albany Law Journal of Science and Technology, Forthcoming) on SSRN. Here is the abstract:

Since the decision in Frye v. United States, polygraph results have been deemed inadmissible as evidence in many state and federal courts across the United States. Exclusion has been justified based on purported scientific weaknesses of the test, or the assertion that to allow polygraph evidence would usurp the jury’s role as the arbiter of credibility, wreaking havoc on the American judicial system. This paper suggests that the extensive body of literature on polygraph evidence fails to understand the actual reason polygraph evidence has been an evidentiary pariah. First, this article systematically demonstrates that the justifications for excluding polygraph evidence at trial are equally applicable to nearly every other forensic science except DNA analysis. Second, this paper asks the novel question, “Why is polygraph evidence held to such a different standard?” This article suggests that the only significant difference between many routinely admitted forensic techniques and polygraph evidence is the party most frequently offering the evidence. This article then considers several possible explanations for why this fact matters in judges’ decisions. Finally, this article concludes that because science and law have little to do with the exclusion of polygraph the trend is likely to continue regardless of technological advances.

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This is a bizarre article at this particular historical moment. The author says polygraph should be accepted because bitemarks, fingerprints, and other comparative forensic disciplines have historically been accepted based solely on the assessment of practitioners instead of scientists, but we're in an era when the best research on the topic is demonstrating that those comparative disciplines have little scientific basis and much higher error rates than was previously supposed.

So because junk science has been used in the past, we should let in MORE questionable evidence instead of seeking to validate iffy forensic techniques already in use? We should use polygraphs if polygraph examiners say they're reliable and ignore scientists in the fields underlying the technology's assumptions? Really? This article takes the conclusion of the NAS forensics report that many modern forensics don't stand up to scientific scrutiny and uses that to argue for wider use of questionable techniques. That's messed up.

Posted by: Gritsforbreakfast | Oct 1, 2011 6:08:02 AM


Thank you for your comments. However, it appears that you misunderstand the thrust of the article. The purpose of this article is not to advocate for the use of polygraph evidence in courtrooms. In fact, I take no stance on the propriety of the use of this evidence at all. This article makes the comparison between polygraph evidence and several forms of "junk science" (science that has been criticized by the NRC) to illustrate an inconsistency in courts' assessment of scientific evidence.

The courts are quite willing to continue to accept evidence of questionable validity, dismissing the admonitions of the NRC and its report. Yet, these same courts are quick to point out the "fatal" flaws of polygraph evidence, remaining steadfast in their denial of the right to present the evidence. This article is written in an effort to understand why these courts continue to admit significant amounts of "junk science" (including those disciplines criticized in the 2009 NRC report), while keeping one particular form of evidence out. The comparisons are not meant to suggest that polygraph evidence should be admissible, but to illustrate that many of the assertions offered for excluding polygraph evidence are not unique to that type of evidence, are incorrect based on social scientific knowledge, and could be addressed reasonably easily. Thus, it seems logical to conclude that science has little to do with these courts’ admissibility rulings. Instead, there is an apparent effort exclude evidence that may help the defendant and, implicitly, admit any evidence that helps the prosecution, regardless of the quality of the science underlying the evidence.

If anyone sees a different rationale for these evidentiary rulings, I would be interested to hear his/her thoughts.

Posted by: Adam B. Shniderman | Oct 11, 2011 3:49:31 PM

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