Legal Commentary

Over the last decade, neuroscientists have made significant strides toward using various brain imaging techniques to determine when a subject is lying.    The research is still at early stage, however, and has principally involved rather artificial experimental settings (e.g., college students instructed to lie about the suit of a playing card).  If you ask most neuroscientists, they will say that we are quite far from having an all-purpose technique that can provide admissible evidence in court.  Indeed, a couple of courts have already refused to admit brain imaging evidence of credibility/deception (see Wilson, Semrau).

In my view, the test of whether we should admit some technology in court depends on whether, by introducing the technology, we achieve better outcomes overall.  That's a very difficult determination to make.  It depends on the quality of the science, the ability of judges and jurors to interpret the science, financial costs associated with the technology, various risks of abuse, and so on.  And there is a fair question about what legal standard judges should use to achieve our overarching goal.  But surely, as Fred Schauer points out, the technology need not be perfect to be helpful in real world forensic settings.

Even if we are still a long way away from developing reliable lie detectors, there is a substantial probability that we will have reasonably good lie detectors within the next thirty years.  Those prospects should arguably change our behavior even today.  For in thirty years, we can surely ask you about your conduct over the course of your lifetime: Have you ever cheated on your taxes?  Have you ever cheated on your spouse?  Did you bury the body by the river? 

Under what I describe here (p.118-20) as the technological "look-back principle," we should already consider the privacy protections we are likely have in the future in order to decide how to behave today.  (At least until we develop good means of forgetting what we already know!)

Of course, not all of our privacy interests are amenable to legal regulation.  Nothing will stop your lover from testing your fidelity in a brain scanner as a condition of continuing the relationship.  Many campaigning politicians already disclose their tax returns, even when they have no legal obligation to do so.  Perhaps, someday, politicians will agree to be scanned while they answer questions like: Have you ever knowingly misreported campaign funds?  Have you ever accepted a bribe?  Did you bury the body by the river?  No doubt many criminal offenders were surprised by the look-back potential of DNA.  Perhaps we'll all be taken by surprise, someday, by the look-back potential of lie detectors.