In law, we frequently refer to the “burden of proof”. This legal term refers to how much proof the prosecutor or plaintiff needs before he/she can obtain a ruling against the defendant. Two of the most common “burdens” are “preponderance of the evidence” and “beyond a reasonable doubt”.
Preponderance of the evidence is most frequently used in civil cases, although it is also used in criminal proceedings as well. It means “more likely than not”. Put another way, if it is 51% likely that the defendant committed the alleged act, he is liable. With respect to criminal proceedings, this burden in sometimes used during hearings, such as a California probation violation hearing.
The reason that a civil burden is used in criminal hearings is because these proceedings don't afford criminal defendants as much protection as criminal trials do. Using the example above, this means that the prosecutor must only prove that it is more likely than not that a defendant violated his probation in order to find him guilty during a California probation violation hearing.
Beyond a reasonable doubt is the typical criminal burden of proof…and a bit trickier to define. It basically means that if there is no reasonable explanation other than the fact that the defendant committed the alleged act, then he must be guilty. This is the burden that is exclusively used during criminal trials, as it is California's highest burden of proof.