In ANI V THE STATE (2002) 10 NWLR PT 776 644, this Court had this to say; The burden on the accused to prove his insanity, however is merely as in civil cases that is to say on the balance of probability or the preponderance of evidence.
WHAT IS REQUIRED TO PROVE INSANITY
In order to succeed in a plea of insanity, the Appellant must before the trial Court, prove on the balance of probability that as at the time of committing the offence, he lacked the capacity to; 1. Understand what he was doing 2. Control his actions 3. Know that he ought not to act or...