In the law of evidence, a presumption of a particular fact can be made without the aid of proof in some situations. The types of presumption includes a rebuttable discretionary presumption, a rebuttable mandatory presumption, and an irrebuttable or conclusive presumption. The invocation of a presumption shifts the burden of proof from one party to the opposing party in a court trial. Presumptions are sometimes categorized into two types: presumptions without basic facts, and presumptions with basic facts. In the United States, mandatory presumptions are impermissible in criminal cases, but permissible presumptions are allowed.
The ancient Jewish law code, the Talmud, included reasoning from presumptions (hazakah), propositions taken to be true unless there was reason to believe otherwise, such as "One does not ordinarily pay a debt before term." The same concept was found in ancient Roman law, where, for example, if there was doubt as to whether a child was really the issue of someone who had left money in a will, the presumption was in favour of the child. Medieval Roman and canon law graded presumptions according to strength: light, medium or probable, and violent. These gradings and many individual presumptions were taken over into English law in the seventeenth century by Edward Coke.
A number of presumptions are found in most common law jurisdictions. Examples of these presumptions include:
The presumption of death. A person who has been absent for seven years without explanation and "gone to parts unknown" is presumed dead at common law. The time period it takes for the presumption to arise has often been modified by statute.
The presumption of innocence, which holds that the prosecution bears the burden of proof in a criminal case, and that the accused has no obligation to introduce evidence until the prosecution has made a prima facie case.
A presumption of survivorship has referred to a number of different presumptions. The term is sometimes used to refer to presumptions that one or another of two persons lived the longer when they died together in the same accident. The presumption that two or more people who establish a joint account intend for the survivors to have the assets put into the fund upon the death of one of the joint account holders has also been called the "presumption of survivorship".
The presumption of mailing presumes that a properly addressed letter delivered to the post office or a common carrier was in fact delivered and received by the addressee.
In the law of the United States, the presumption of constitutionality presumes that all statutes are drafted in accordance with Federal and state constitutional requirements. The party challenging the constitutionality of a statute bears the burden of proof, and any doubts are resolved against that party. If there are two reasonable interpretations of a statute, one of which is constitutional and the other not, the courts will choose the path which permits upholding the statute.
^J. Franklin, The Science of Conjecture: Evidence and Probability Before Pascal (Baltimore: Johns Hopkins University Press, 2001), 6.
^Technically, the presumption of innocence is not a presumption, but rather is a rhetorical expression emphasizing the fact the prosecution bears the burden of proof in a criminal case. The accused has no obligation to adduce evidence in his or her favor and will be automatically acquitted unless the prosecution surmounts its evidentiary threshold (the burden of proof, which in the United States is generally beyond a reasonable doubt in criminal cases). See presumption of innocence.