"Anyone who has proclaimed violence his method inexorably must choose lying as his principle."--Aleksandr Solzhenitsyn (1)
Perhaps even more than civil proceedings, the criminal trial demands the truth. For one, the stakes are simply too high to brook prevarication. If a person misleads the court in a criminal trial, the defendant may lose his liberty or even his life. Alternatively, the community will see its interests in justice and security undercut if the guilty are let free due to specious testimony. Finally, fulfillment of the prosecutor's unique duty in criminal proceedings to arrive at the correct outcome--be it conviction, acquittal, or dismissal of the charges--depends on the veracity of the information that the prosecutor receives and ultimately provides to the courts. Each of these actors has a vested interest in ensuring that the tribunal hears only the truth.
Accompanying these interests, however, are concerns that individuals may have compelling motives to lie. The culpable defendant may do so to avoid imprisonment or death. Witnesses for the government or the defense may deceive the court to procure leniency in their own proceedings, to cover up their own involvement in criminal activity, or to help a friend, family member, or associate escape punishment. Clearly, dissemblance by any of these actors can vitiate a verdict and carries the potential for gross injustice.
In light of these concerns, any assistance that science can provide in sifting truth from deceit serves to enhance the integrity of the criminal trial. Proponents of the polygraph (long referred to as the "lie detector") have for many years argued that they already had at their disposal a tool to scientifically assess a subject's veracity. The courts, however, generally disagreed. Polygraph evidence was barred outright as insufficiently reliable in many jurisdictions and made exceedingly difficult to introduce in others. (2)
Scientists and lawyers convinced that accurate, admissible lie detection was possible refused to give up the ghost. After the polygraph's prospects were deemed unlikely to improve, they turned to other technologies. Within the last decade, they have grown increasingly excited about a new breed of lie detectors, which they hope can succeed where the polygraph failed. These devices have been grouped together under the nebulous moniker of "neuroimagery." (3) This next generation, however, encompasses multiple approaches, and the term belies the technological diversity that the new machines represent. Yet they share a reliance on recent advancements in neuroscience and new insights into how the brain processes information in their attempt to determine whether the individual under examination is lying. What remains to be seen is whether the courts will be more disposed to admitting test results from these devices in criminal trials. To date, this question is largely unanswered.
This article will focus on two types of neurotechnology that carry the potential for admissibility in criminal proceedings: functional Magnetic Resonance Imaging (fMRI) and brain fingerprinting. After a brief survey of how neuroimaging may be applied in the criminal justice system, the article addresses the recent surge of interest in applying these technologies to lie detection. It continues by introducing the scientific underpinnings of fMRI and brain fingerprinting to provide a baseline understanding of how they work and the extent to which they differ from their less successful antecedents. Next, two obstacles to the admissibility of scientific testimony posed by standard rules of evidence will be examined, followed by a review of how the familiar precursor to these technologies--the polygraph--largely failed in its quest for acceptance by the courts. Finally, the article assesses the prospects of fMRI and brain fingerprinting transcending the polygraph's checkered past to bring truth-testing by scientific means before the courts with regularity. …