LEGAL PRINCIPLE: CRIMINAL LAW — Defences — Insanity — Elements to Establish
PRINCIPLE STATEMENT
To establish insanity, the defence must show: (1) mental disease or natural mental infirmity; and (2) that it deprived the accused of capacity to understand his actions, control his actions, or know that he ought not to do the act.
RATIO DECIDENDI (SOURCE)
Per Katsina-Alu, JSC, in Ani v. State (2002) NLC-3152001(SC) at p. 3; Paras D–E.
"In order, therefore, to establish the defence of insanity, the defence must first show that the accused was at the relevant time, suffering from either mental disease or from a 'natural mental infirmity.' Then it must be established that the mental disease, or the natural mental infirmity as the case may be, was such that, at the relevant time, the accused was, as a result deprived of capacity: (a) to understand what he was doing; or (b) to control his actions; or (c) to know that he ought not to do the act or make the omission."
EXPLANATION / SCOPE
The defence of insanity has two elements: (1) mental disease or natural mental infirmity; (2) resulting incapacity to understand, control, or know wrongfulness. The accused must prove both elements. The standard is the balance of probabilities. The principle is based on the M’Naghten Rules as codified in the Criminal Code. The accused must show a causal link between the mental condition and the incapacity. The court will consider all evidence, including medical reports. The rule applies to all criminal trials. The prosecution may rebut with contrary evidence. The defence fails if either element is not proved.