In NWOYE IGWEZE ONYEKWE v. THE STATE (1988) LPELR 2732 (SC), this Court detailed some of the guiding principles in establishing insanity viz: 1. Evidence as to the past history of the accused. 2. Evidence as to his conduct immediately preceding the killing of the deceased. 3. Evidence from Prison Warders who had custody of the accused and looked after him during his trial. 4. Evidence from Medical Officers and/or Psychiatrists who examined the accused. 5. Evidence of relatives about the general behaviour of the accused and the reputation he enjoyed for sanity or insanity in his neighbourhood. 6. Evidence showing that insanity appears in the family history of the accused. See also UDOFIA v. STATE (1988) LPELR 3305 (SC).
INSANITY IS PROVED ON THE BALANCE OF PROBABILITY
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.