Mind Reading (Part 1 of 2): Neuroscience in the witness stand

'But officer, my brain made me do it!' Brain scans are becoming commonplace as evidence in US courts, in the bid to convict offenders or free them. But is the technology half-baked? Can we biologically categorise people as criminals -- mad, bad and dangerous to know? Free will, privacy and personal responsibility are all up for grabs in the collision between science and the law.