Justifying genetics as a possible legal defence to criminal responsibility in Nigeria

  • Oluwatomi A. Ajayi
  • Ikenga K.E. Oraegbunam
Keywords: MAO-A, Criminal Responsibility, Environment, Genetics, Legal Defence, XYY


The saying that criminals are born rather than made seems to rekindle the anthropological debate on the relationship between nature and nurture (genes versus environment). This is the controversy as to whether every individual is the product of his genes or his environment or both. However, jurisprudence of many criminal cases tends to question whether a person’s inherited genes predispose him to violence and further determine his criminal responsibility in law. Under the Nigerian criminal law, the legal test of criminal responsibility is mainly whether the accused person intends the consequence of his act or whether he truly knows if what he was doing is right or wrong. Over time, those who commit murder due to one psychotic or hereditary mental disorders end up with an insanity acquittal, therefore leaving genetics out of the question. This is primarily because genetics is not recognised as a legal defence in Nigeria. It is also a new terrain which has not been explored by the courts probably because the area is complex and strictly scientific. However, in some western societies, the abnormal Monoamine Oxidase A (MAOA) gene and XYY chromosome have been held to be linked with crime. This paper tries to justify the inclusion of such abnormal genetic disturbance as a possible legal defence in the Nigerian criminal justice system. The methodology is doctrinal with primary and secondary sources which are based on extensive and explanatory study of Nigerian criminal laws, medical and psychology textbooks, scientific journals, judicial decisions, discussions with few doctors and online materials. These findings indicate that Nigeria may not yet be ready to explore genetics as a legal defence because insanity stands as a valid alternative defence. However, there is hope as the Criminal Law of Lagos State 2011 has indirectly associated with genetics through its provision on diminished responsibility.

Keywords: MAO-A, Criminal Responsibility, Environment, Genetics, Legal Defence, XYY


Journal Identifiers

print ISSN: 2276-7371