Law is said to be as old as society itself. Since when men began to live in groups, there arose the need to establish rules and conducts and for sanctions to be applied when the rules are broken. In the same vein, the history of medicine is as ancient as man. Man has found the cure for various ailments since early civilization from herbs. Under the traditional African system, the use of supernatural powers and other traditional methods play not only a prominent role, but a crucial one in the administration of justice before the advent of the British. In Africa generally, people believe in the efficacy of such powers, beliefs and traditional methods in many areas especially in crime detection and protection. In more modern times, the uses of scientific practices have been introduced into the criminal and legal process. In particular, in crime detection, traditional African legal system show that various methods ranging from taking of obnoxious substance, herbal concoctions, to indulging in certain harmful practices which are detrimental to human health have been adopted to prove the innocence or otherwise of an accused person. In modern times, basic and applied science has been specifically adapted to legal proof. This paper considers methods of crime detection under the traditional African system, the modern use of scientific methods of proof and the health implications.