CrimProf Blog

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

Thursday, September 3, 2009

On Schauer on Brain-Based Lie Detection (Kolber)

Kolber Over the last several years, researchers have been trying to develop brain-based methods of detecting lies.  The overwhelming consensus among neuroscientists is that such techniques are unreliable, particularly in real-world settings.  That hasn't stopped at least a couple of companies from marketing functional magnetic resonance imaging ("fMRI") lie detection services.  See here and here

While the consensus view is probably right that the technology is not yet ready for primetime, there is a perhaps unwarranted pessimism that pervades many of these discussions.  I've been to numerous conferences where academics love to identify problems with the reliability of fMRI-based lie detection and emphasize that jurors are likely to be unduly swayed by neuroscience evidence.  They often seem to forget that our most well-known method of lie detection--the jury--has numerous reliability problems.  Most importantly, despite hundreds of years of data, we can't say very well just how reliable juries are.  Surely juror lie detection leads to false positives and false negatives, but this particular "technology" is widely used in the United States. 

Of course, litigants have constitutional rights to jury trials that they don't have to modern lie detection techniques.  But from a policy perspective, we want to know whether a new approach to lie detection, when combined with whatever other truth-generating techniques we already use, leads to cost-effective improvements in the judicial system.  That policy question, at least on the surface, looks rather different than the legal issue of whether the technology satisfies the standards for admission of scientific evidence set out in the Daubert or Frye test.

With these considerations in mind, I was pleased to read Fred Schauer's (Law, UVA) new draft article, Can Bad Science Be Good Evidence: Lie Detection, Neuroscience, and the Mistaken Conflation of Legal and Scientific Norms.  Schauer points out, quite appropriately, that the standards for the admission of legal evidence are determined as a matter of policy not scientific inquiry.  Neuroscientists can tell us whether a particular technology satisfies an existing legal standard but have no special expertise, as a general matter, in selecting the standard itself. 

Schauer states, "Some examples of good science may still not be good enough for some legal purposes, and, conversely, some examples of bad science m[a]y, in some contexts, still be good enough for some legal purposes."  His draft, therefore, seems to cut to the heart of the Daubert and Frye standards.  Perhaps, given the ways that scientific evidence may unduly sway juries, we need something like the Daubert and/or Frye standards, so that, at the end of the day, we reach the right policy outcomes.  But Schauer is not so pessimistic about juror abilities.  He suggests, at least implicitly, that in the lie detection context, the traditional tests for admitting scientific evidence may not set the bar at the right place.


(Hat tip for the SSRN link: Kevin Cole); (Cross-posted.)

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I think it's a rather narrow and limited view of juries to suggest that their essential function is to serve as lie detectors. Certainly, making such credibility decisions is within a jury's purview. But that's a far cry from claiming they are are some type of biochemical truth machine. Truth determination is only a tiny portion of the reason juries exist.

Posted by: Daniel | Sep 3, 2009 12:59:54 PM


I don't see anything above that says that the only function or even that the "essential" function of juries is to assess truthfulness. That being said, credibility assessments surely are a very important part of what juries do.

Posted by: Adam Kolber | Sep 4, 2009 6:27:20 AM

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