Burden of proof is a legal duty resting upon a party litigant, at some stage in the trial of a civil case.  The legal duty is to introduce evidence of preponderating weight on an issue which s/he asserts, to overcome the proof offered on that issue by the opposite party.  The term burden of proof is derived from the Latin term “onus probandi”.  Burden of proof is the obligation placed upon a party to prove or disprove a disputed fact.   Generally, the burden of proof is satisfied by evidence.

The principle of burden of proof is associated with the Latin maxim “semper necessitas probandi incumbit ei qui agit”, means: “the necessity of proof always lies with the person who lays charges.”  In civil law cases, the burden of proof requires a plaintiff to convince a judge or jury of the plaintiff’s entitlement to the relief sought.  This means that the plaintiff must prove each element of the claim, or cause of action, in order to recover.  Burden of proof is the most important rule of evidence in the trial of civil cases.  Generally, burden of proof is on the plaintiff to show by a “preponderance of evidence” or “weight of evidence” that all the facts necessary to win a judgment are probably true.

In a criminal trial, the prosecution has the burden of proof to demonstrate that the defendant committed the specified crime(s) beyond a reasonable doubt. This is a higher burden of proof than the civil “preponderance of evidence” standard.

Generally speaking, there are no hard-and-fast standards leading the allocation of the burden of proof in every situation.  Burden of proof is merely a question of policy and fairness.