Every person is presumed to be of sound mind, and to have been of sound mind at any time which comes in question until the contrary is proved. Accordingly, there is no duty on the prosecution in criminal cases to establish what the law presumes in its favor that is to say that, the sanity of an accused persons.
On the contrary, where an accused person pleads insanity or insane delusion as a defense to a criminal prosecution, three is a duty and the onus is on him to rebut this primary presumption of law as to his sanity and to establish his insanity or insane delusion as the case may be within the context of section 28 of the criminal code.
More details on Insanity
To establish a defense of insanity, it must be clearly proved that at the time of committing the act, the accused was laboring under a defect of reason from a diseased mind as not to know the nature and quality of the act he was doing. In proving the insane delusion, the accused need not produce evidence that will convince the judge or jury beyond reasonable doubt, it is sufficient for the accused to discharge this burden on the balance of probability.
For defense to discharge the burden of proof of insanity, evidence must suggest that it was most probable that he suffered from mental disease which deprived him of capacity to understand what he was doing or to control his action.
Having regard to the above provision of our law, the prosecution has no duty to proof that the appellant was sane or insane. The onus is on the defense to establish the defense or plea.
similarly, it was stated Per Akpata J.S.C. in the case of EJIZIMA V. STATE43 that the onus to overcome the presumption that everyman is sane and accountable for his action, rests on the accused. To sustain the defense, the Defense counsel must proof which could include among others, positive acts of the accused, before and after the
dead complained of, evidence of a doctor who examined and watched the accused over a period of time as to his mental state; evidence of relations who knew the accused person intimately relating to her behavior and the change which has come upon her, the medical history of the family which could indicate hereditary mental application or abnormality, and such other facts and circumstances which will help the trial judge come to the conclusion that the burden of proof of insanity, placed by the criminal code on the defense has been amply discharged.
Similarly, in Onyekwe V. the state, Oputa J.S.C gave the ingredient of the defense of insanity:
- Evidence as to the past history of the accused
- Evidence as to his conduct immediately preceding the killing of the deceased.
- Evidence from prison warders who had custody of the accused and looked after him during his trial.
- Evidence of medical officers and/or psychiatrist who examined the accused.
- Evidence of relations about the general behavior of the accused and the reputation he enjoyed for sanity or insanity in the neighborhood.
- Evidence showing that insanity appears in the family history of the accused.
- Evidence of the insanity of his ancestors or blood relations is admissible but medical evidences though probative, is not essential.The problem however in relying on the evidence of relations only without medical report or evidence is that there are certain traits in human beings, to varying degree, which sometimes mistaken for insanity. Some of them are irascibility, irritability, eccentricity and quarrelsomeness. Persons affected with any of these traits to a high degree, are easily spurred to violence and wrongly regarded as being insane by the uninformed.
The duty to decide whether the appellant is of unsound mind or not is that of the trial judge who by law is not bound by the certificate of the medical officer to the contrary although, naturally great weight ought to be attached to the medical opinion.