Generally used to describe the threshold that a party seeking to prove a fact in court must reach in order to have that fact legally established. For example, in criminal cases, the burden of proving the defendant’s guilt is on the prosecution, and they must establish that fact beyond a reasonable doubt. In civil cases, the plaintiff has the burden of proving his case by a preponderance of the evidence.
The burden of proof is often said to be comprised of two distinct but related concepts: the burden of production, and the burden of persuasion.