Forensic psychology
The ancient Greeks and Romans were the ones to first introduce the concept of insanity to the law. One of the first cases was Rex v. Arnold in 1723 in which Edward Arnold "Mad Ned" shot and injured Lord Onslow.  As a result, Edward Arnold was found guilty and sentenced to death.  But, Lord Onslow was not satisfied with this decision and said instead he should remain in prison for life. The judge ruled in his favor and that the behavior after the crime was admissible.  This ruling set the stage for future trials to consider medical testimony and examinations performed after the crime.