An assumption of human free will is fundamental for any system of legal accountability. Unfortunately, the more the cognitive sciences develop, the more they suggest that our moral reasoning lies largely outside of our control—and can even be manipulated.
An example is transcranial magnetic stimulation. Experiments with TMS reveal that you canalter somebody’s moral reasoning using a powerful magnet. Unscrupulous military leaders could artificially distort their subordinates’ morality for the worse by attaching a TMS unit to their helmets. Yet if a soldier committed war crimes because somebody else had turned off his morals, it is hard to see how we could hold him responsible for his actions.
From “Who Will Be Accountable for Military Technology?” by Paul Robinson.