Presumptions & Inferences

Since I’ll be revisiting the following four concepts in various epistemological arguments in the future, especially those pertaining to alleged miracles, I thought it would be good to introduce them now.

From Criminal Law, 3rd Ed., Arnold H. Loewy, p.209–212:

It is important to understand the differences between the following concepts:

1) inference (permissive presumption);

2) mandatory presumption requiring some evidence in rebuttal (burden of production);

3) mandatory presumption shifting the burden of proof; and

4) conclusive presumption.

An inference (permissive presumption) is a fact which a jury may but need not infer. […] A mandatory presumption requiring some evidence in rebuttal does not shift the burden of proof. Rather it requires a jury to accept certain facts as true unless some evidence has been introduced in rebuttal. To illustrate, in most jurisdictions when a jury finds beyond a reasonable doubt that the defendant intentionally killed the victim, the jury is under a duty to find the defendant guilty of murder unless some evidence of justification, excuse, or mitigation is introduced. […] A mandatory presumption shifting the burden of proof differs from a mandatory presumption creating a burden of production in that the burden of proof remains with the party against whom the presumption operates. The Maine procedure invalidated in Mullaney v. Wilbur is a good example. Once the State proved an unlawful intentional killing, malice aforethought was presumed until the defendant proved that it was more likely than not that he acted in a justifiable heat of passion. Merely introducing some evidence of heat of passion would not have rebutted that presumption.

Finally, a conclusive presumption is simply a rule of law. It requires a jury to find fact B if it has found fact A. […] An inference (permissive presumption) is constitutionally permissible if there is a rational connection between the proven fact and the presumed fact, and the presumed fact is more likely than not to follow from the proven fact.