“Brains on Trial”: Research on Groups & Concern for Individuals

By Matthew L Baum

What are the implications of advances in brain science for the justice system? This was the topic of a panel discussion held Tuesday at MIT’s McGovern Institute and moderated by Alan Alda in conjunction with the premier of his new PBS special, “Brains on Trial”. The  discussion ranged from using fMRI for lie-detection to using it to help determine the reliability of an eye-witness.

In general, the panel rightly pointed out practical limitations of these technologies. Panelist Nancy Kanwisher highlighted, for example, that research on lie-detection is done in a controlled, non-threatening environment from which we may be unable to generalize to criminal courts where the stakes are high.

While I was sympathetic to most of this discussion, I was puzzled by one point that the panel raised several times: the problematic nature of applying data based on a group of people to say something about an individual (e.g., this particular defendant). To present a simplified example: even if we could rigorously show a measurable difference in brain activity between a group of people who told a lie in the imager and a group of people who told the truth, we cannot conclude that an individual is lying if he shows an activity pattern similar to the liars. Since the justice system makes decisions on individuals, therefore, use of group data is problematic.

To me, this categorical objection to group data seems a bit odd, and this is why: I can’t see how group data is conceptually different from ordinary circumstantial evidence. Read More