Insanity and Criminal Responsibility in Nigerian Law
In criminal law, “insanity” is a legal term, not a medical one. You can be medically ill but legally sane. Or legally insane due to conditions medicine classifies differently (like sleepwalking). The insanity defense challenges a basic requirement for criminal guilt: the ability to reason and choose. Section 28 of the Criminal Code defines this defense. It’s broader and more humane than the English M’Naghten Rules it came from.
Everyone Is Presumed Sane
Section 27 of the Criminal Code says: “Every person is presumed to be of sound mind… until the contrary is proved”.[^1] This mirrors the M’Naghten Rules. The accused must prove insanity. Unlike the prosecution (which must prove guilt beyond reasonable doubt), the accused only needs to prove insanity on the balance of probabilities—more likely than not.
Section 28: Three Ways to Be Legally Insane
Section 28 says you’re not criminally responsible if, when you committed the act, mental disease or natural mental infirmity took away one of three capacities. This section is broader than M’Naghten, which only looked at defects in reasoning.
1. Understanding What You’re Doing
This is about perceiving reality correctly. “Understand” in the Code is wider than “know” in M’Naghten.
Example: A man slices someone’s throat thinking he’s slicing bread. He knows he’s using a knife, but his delusion prevents him from understanding the act’s nature—that stabbing someone kills them.
2. Knowing It’s Wrong
This tests whether you understand the act is morally or legally wrong. There’s debate over whether “wrong” means illegal or immoral.
R v Windle: A man poisoned his wife and said “I suppose they will hang me for this.” He was convicted because he knew it was legally wrong, even if he felt morally justified.[^2]
Nigerian law: Following the Australian case Stapleton v R, Nigerian courts tend to say “wrong” includes moral wrongness—the inability to tell good from evil. Section 229 of the Criminal Procedure Act supports this by distinguishing “wrong” from “contrary to law.”
3. Controlling Your Actions
This is Nigeria’s most progressive feature. Section 28(c) allows a defense if mental disease made you lose control over your actions, even if you knew they were wrong.
Irresistible impulse: In R v Omoni,[^3] the Court of Appeal said this allows a defense of “irresistible or uncontrollable impulse.”
Example (Echem v R): Medical evidence showed the accused had mental attacks after a head injury. During these attacks, he couldn’t control himself, even though he might have known his actions were wrong. The defense succeeded.[^4]
Natural Mental Infirmity
Section 28 includes “natural mental infirmity”—a term not in M’Naghten.
Definition: In R v Omoni, the court defined this as “a defect in mental power neither produced by his own default nor the result of disease of the mind.”[^5]
What it means: In R v Tabigen,[^6] the court said this refers to arrested or incomplete mental development before age 18.
Must be natural: The condition can’t be self-induced. In R v Alice Eriyamremu,[^7] a woman killed her albino grandchild and blamed witchcraft. The court said any mental problem she had came from worshipping juju (her own doing), not a “natural” condition.
Internal vs. External Causes
Courts distinguish between insanity (internal causes) and automatism (external causes).
Internal (insanity): Conditions from inside your body—arteriosclerosis (R v Kemp), epilepsy (R v Sullivan), high blood sugar from not taking insulin (R v Hennessy). These lead to “Not Guilty by Reason of Insanity” and confinement in a mental facility.
External (automatism): Conditions from outside—head injuries, hypnosis, low blood sugar from taking insulin but not eating (R v Quick). These lead to simple acquittal.
Partial Insanity: Delusions
The second part of Section 28 deals with people who aren’t fully insane but have specific delusions. If you have a delusion about specific facts, you’re judged as if those facts were real.
Iwuanyanwu v State: The accused killed someone he believed was sending evil spirits to kill him. The court said even if spirits were being sent, ambushing and killing the person wouldn’t be self-defence. He was convicted of murder.[^8]
Conclusion
Section 28 goes beyond M’Naghten. By recognizing loss of control (irresistible impulse) and natural mental infirmity, Nigerian law acknowledges that willpower can be as damaged as reasoning. Cases like Omoni and Tabigen ensure the law punishes the guilty, not the mentally ill.
[^1]: Criminal Code Act, Cap C38, Laws of the Federation of Nigeria 2004, s 27.
[^2]: R v Windle [1952] 2 QB 826.
[^3]: R v Omoni (1949) 12 WACA 294.
[^4]: Echem v R (1952) 14 WACA 164.
[^5]: R v Omoni (n 3).
[^6]: R v Tabigen (1960) SCNLR 201.
[^7]: R v Alice Eriyamremu (1959) 4 FSC 90.
[^8]: Iwuanyanwu v State (1964) NMLR 269.
