The advent of new imaging techniques is broadening our understanding o
f the major psychiatric illnesses. The increased knowledge of brain fu
nction will have consequences for the expert medical witness who has t
o give evidence in court. Both the insanity defence and the defence of
automatism depend on disorders of the mind. Psychiatry is now able in
many cases to produce evidence that these are consequent upon disorde
rs of the brain. In presenting evidence in court there is an apparent
conflict between 'brain words' and 'mind words'.