Section 137 of the Evidence Act, 2004 provides for the burden of proof in civil cases. The burden of first proving the existence of a fact lies on the party against whom the judgment of the court could be given if no evidence were produced on either side, regard being had to any presumption that may arise on the pleadings. If such party adduces evidence which might reasonably satisfy a court that the fact sought to be proved is established, the burden lies on the party against whom judgment would be given if no more evidence were adduced; and so on successively until all the issues in the pleadings have been dealt with. Where there are conflicting presumptions, the case is the same as if there were evidence. By section 137, the burden of proof is not static. It fluctuates between the parties. Subsection (1) places the first burden on the party against whom the court will give judgment if no evidence is adduced on either side. In other words, the onus probandi is on the party who would fail if no evidence is given in the case. Thereafter, the second burden goes to the adverse party by virtue of subsection (2). And so the burdens change places almost like the colour of a chameleon until all the issues in the pleadings have been dealt with. By section 137(2), the burden of proof shifts between the parties in the course of giving evidence in the proceedings. From the language of the subsection, there is some amount of versatility in the shifting process of the burden. The shifting process, in the language of the subsection, will be so on successively until all the issues in the pleadings have been dealt with. Section 139 of the Evidence Act provides for the proof of a particular fact. By the section, the burden of proof as to any particular fact lies on the person who wishes the court to believe in its existence, unless it is provided by any law that the proof of that fact shall lie on any particular person, but the burden may in course of a case be shifted from one side to the other. In considering the amount of evidence necessary to shift the burden of proof, regard shall be had by the court to the opportunity of knowledge with respect to the fact to be proved which may be possessed by the parties, respectively. (See Abdul-Raham v Commissioner of Police (1971) NMLR 87; Arase v Arase (1981) 5 SC 33; Savannah Bank of Nigeria Ltd v Pan Atlantic Shipping and Transport Agencies Ltd (1987) 1 NWLR (Part 49) 212 and Fadlattah v Arewa Textile Ltd (1997) 8 NWLR (Part 518) 546).
— Niki Tobi, JSC. Buhari v. INEC (2008) – SC 51/2008