Of the numerous Latin phrases that have crept into law, the maxim res ipsa loquitur is perhaps the best known. Yet, this innocuous phrase, which means nothing more than "the thing speaks for itself," has been the source of much confusion and disagreement. This divergence of opinion is centred around the proper application and the procedural effect of the rules which have been promulgated by the courts in giving effect to and in applying this phrase. This study therefore has the objective of critiquing the application of the doctrine in Nigeria. In doing this, it examines instances of its use and also conducts a comparative analysis with the Jurisdictions of England and the United States of America, which courts are seen as well developed and thought leaders in this direction.

The principle of Res Ipsa Loquitur is simple, whereas in a case of negligence, the plaintiff must prove by evidence, regarding the defendant’s conducts, that the defendant was negligent, but when the plaintiff does not know how and why the accident happened, in such a case the plaintiff can invoke the assistant of the rule of evidence known by the latin maxim Res ipsa loquitur (“the event speaks for itself”), thereby shifting the burden of proof to the defendant, to prove that they were not negligent.

Since its inception, the doctrine of res ipsa loquitur has produced conflict, confusion, and doubt. In Nigeria, the requirement under which the doctrine of “res ipsa loquitur” becomes operative includes firstly, proof of the happening of an unexplained occurrence, secondly, the occurrence must be one which would not have happened in the ordinary course of things without negligence on the part of somebody other than the plaintiff, and lastly, the circumstances must point to the negligence in question being that of the defendant rather than that of any other person.

Findings revealed that compared to the other two legal systems used as basis, there is legal clarity with regard to the nature, requirements for and especially the effect of the application of the doctrine on the onus of proof in Nigeria. The approach followed by the courts is that the doctrine of res ipsa loquitur is a permissible factual inference which the court is at liberty but not compelled to make and which does not affect the onus of proof, which can either be with the plaintiff or the defendant.  Normally the onus of proof of the negligence alleged at the onset is on the plaintiff, but where this doctrine is applicable, after evidence of how the accident occurred is given by the plaintiff, the onus shifts on the defendant to offer an explanation as to why the accident happened. Such explanation would seek to show that the defendant is not at fault.

It is also quite clear that in Nigeria, the plaintiff can only rely on the doctrine if the cause of the accident remains unknown, whereas in America, the doctrine can still hold if the plaintiff has partial knowledge of the cause. On rebuttal by the defendant, the nature of the explanation is such that although it should conform to certain rather stringent principles it is not expected of the defendant to prove his blamelessness on a balance of probabilities. This implies that if, after all the evidence is in, the probabilities are still equal, the defendant should prevail.

Conclusively, the doctrine of res ipsa loquitur is basically an application of principles of circumstantial evidence. The traditional elements that must be shown by a plaintiff who seeks to invoke the doctrine are merely factors by which the defendant may be so closely connected with the fact of plaintiff's injury as to make the inference that his negligence caused the injury more plausible than any other.