The question of whether brain scanning can detect the intentions of a criminal defendant fascinates cops, lawyers and John and Jane Doe. It's probably still a theoretical question and may remain so for a long time to come.

Even so, Alan Alda moderated a panel of experts whose members spend a lot of time on the issue of scanners and criminal intent. Watch this session from the World Science Festival that took place on the afternoon of June 1.

On the panel were Nita A. Farahany, a scholar from Duke Law School who studies the legal and social implications of the biosciences, Kent Kiehl, who has amassed the largest database containing brain scans of prisoners, Jed S. Rakoff, a federal judge, and Anthony D. Wagner, a Stanford University memory researcher.