Can Bad Science Be Good Evidence: Lie Detection, Neuroscience, and the Mistaken Conflation of Legal and Scientific Norms

40 Pages Posted: 13 Aug 2009 Last revised: 4 Aug 2015

Frederick Schauer

University of Virginia School of Law

Date Written: August 13, 2009


As the capabilities of cognitive neuroscience, in particular functional magnetic resonance imaging (fMRI) 'brain scans,' have become more advanced, some have claimed that fMRI-based lie-detection can and should be used at trials and for other forensic purposes to determine whether witnesses and others are telling the truth. Although some neuroscientists have promoted such claims, most aggressively resist them, and arguing that the research on neuroscience-based lie-detection is deeply flawed in numerous ways. And so these neuroscientists have resisted any attempt to use such methods in litigation, insisting that poor science has no place in the law. But although the existing studies have serious problems of validity when measured by the standards of science, and true as well that the reliability of such methods is significantly lower than their advocates claim, it is nevertheless an error to assume that the distinction between good and bad science, whether as a matter of validity or of reliability, is dispositive for law. Law is not only about putting criminals in jail, and numerous uses of evidence in various contexts in the legal system require a degree of probative value far short of proof beyond a reasonable doubt. And because legal and scientific norms, standards, and goals are different, good science may still not be good enough for some legal purposes, and, conversely, some examples of bad science my, in some contexts, still be good enough for law. Indeed, the exclusion of substandard science, when measured by scientific standards, may have the perverse effect of lowering the accuracy and rigor of legal fact-finding, because the exclusion of flawed science will only increase the importance of the even more flawed non-science that now dominates legal fact-finding. And thus the example of neuroscience-based lie detection, while timely and important in its own right, is even more valuable as a case study suggesting that Daubert v. Merrill-Dow Pharmaceuticals may have sent the legal system down a false path. By inappropriately importing scientific standards into legal decision-making with little modification, Daubert confused the goals of science with those of law, a mistake that it is not too late for the courts to correct.

Suggested Citation

Schauer, Frederick, Can Bad Science Be Good Evidence: Lie Detection, Neuroscience, and the Mistaken Conflation of Legal and Scientific Norms (August 13, 2009). Cornell Law Review, Forthcoming; Virginia Public Law and Legal Theory Research Paper No. 2009-14. Available at SSRN:

Frederick Schauer (Contact Author)

University of Virginia School of Law ( email )

580 Massie Road
Charlottesville, VA 22903
United States
434-924-6777 (Phone)

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