Liar, Liar Brain on Fire

· 484 words · about 2 minutes

SUPPOSE THERE WAS A MACHINE available for use during a trial that alerted the jury when a witness was lying. Would the use of this machine help or hinder the jury’s analysis of the facts? Would its use promote justice, avoiding unfair treatment of cases?

A machine of this kind is not unworldly, relegated only to science fiction. Advances in neuroscience and functional magnetic resonance imaging (fMRI) devices have isolated specific brain regions associated with truth telling, deception, and false memory. One company, No Lie MRI, advertises to attorneys, claiming its product objectively measures deception using fMRI technology.

There are dissenters, of course, who claim brain images cannot accurately measure truthfulness. Visual depictions of brain activity of the kind produced by fMRI technology, for example, cannot account for false memories, which occurs when a person’s memory of an event does not reflect what actually occurred. Studies have shown people can even falsely remember enter events that never actually occurred. Perhaps more importantly, however, fMRI devices cannot detect intent and cannot determine a statement’s importance, or relevance, to an underlying dispute.

But supposing a machine could accurately, without question, decipher truths from lies, should it be allowed in a courtroom or deposition? One response is that offered by courts, such as the Sixth Circuit in United States v. Semrau, which disallowed fMRI evidence for failing the Daubert test or because its probative value was outweighed by the danger of confusing the jury. (Brain scans, however, are used as mitigating evidence during a criminal defendant’s sentencing proceedings.)

A reason for not allowing brain imaging to determine witness veracity may be this: justice would depend upon the jury’s view, not of the statements, but of what the machine says about the witness statements. It turns out, the best lie detection devices we have are already in use, namely, jurors.

Developed through evolution as a survival skill - there is value in deceiving a predator - the human brain is a finely tuned instrument capable of identifying even the most sincere liar. Studies have shown that people, more accurately than polygraph tests, detect lies. And through everyday interaction and social engagement, people develop and define their lie-detecting capabilities. A jury of one’s peers, as a result, may be the most honest system for administering fairness the judiciary could expect.

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Secrets & Lies: The Legal Ethics of Misrepresentation


Trent Latta is a partner with McDougald Law Group and practices law in Washington and California. He writes frequently on legal issues, including about neuroscience and the law.


Further Reading:

  • The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life, by Robert Trivers
  • Incognito: The Secret Lives of the Brain, by David Eagleman
  • The Future of the Mind: The Scientific Quest to Understand, Enhance, and Empower the Mind, by Michio Kaku
  • Abe, Nobuhito (December 2008). "Neural Correlates of True Memory, False Memory, and Deception,” Cerebral Cortex. 18: 2817.