U.S. National Library of Medicine
We don't have a mind reading machine. But what if we one day did? The technique of functional MRI (fMRI), which measures changes in localized brain activity over time, can now be used to infer information regarding who we are thinking about, what we have seen, and the memories we are recalling. As the technology for inferring thought from brain activity continues to improve, the legal questions regarding its potential application in criminal and civil trials are gaining greater attention.
Last year, a Maryland man on trial for murdering his roommate tried to introduce results from an fMRI-based lie detection test to bolster his claim that the death was a suicide. The court ruled (PDF) the test results inadmissible, noting that the "fMRI lie detection method of testing is not yet accepted in the scientific community." In a decision last year to exclude fMRI lie detection test results submitted by a defendant in a different case, the Sixth Circuit was even more skeptical, writing (PDF) that "there are concerns with not only whether fMRI lie detection of 'real lies' has been tested but whether it can be tested."
So far, concerns regarding reliability have kept thought-inferring brain measurements out of U.S. (but not foreign) courtrooms. But is technology the only barrier? Or, if more mature, reliable brain scanning methods for detecting truthfulness and reading thoughts are developed in the future, could they be employed not only by defendants hoping to demonstrate innocence but also by prosecutors attempting to establish guilt? Could prosecutors armed with a search warrant compel an unwilling suspect to submit to brain scans aimed at exploring his or her innermost thoughts?