The burden of proof in litigation relates to what must be proved and who must prove it. It is different from production of evidence. The rules relating to evidence, which concern the question of how facts may be proved, do not strictly touch on the burden of proof, although sometimes how a fact may be proved may affect what must be proved, particularly when presumptions of fact come into operation. While proof of facts and production of evidence for such proof constitute an important part of litigation even in international law, the success of a party to litigation will also depend to a large extent on the burden of proof that party carries, in so far as, if he carries the burden, he must adduce adequate evidence to prove on balance what he must prove, whereas if he does not carry the burden, the facts will be assumed to be in his favour until the other party adduces adequate evidence to prove the contrary.

In the case of the local remedies rule, it has been seen that the rule has a certain scope and that there are also certain limitations on the rule, and circumstances in which the rule is inapplicable. When the contention is raised by the respondent, as is usually the case, that the alien has not exhausted local remedies, questions arise as to the burden of proof, particularly because limitations to the rule may be pleaded, but also in relation to the actual scope of the rule.