A conclusion made as to the existence or nonexistence of a fact that must be drawn from other evidence that is admitted and proven to be true. A RULE OF LAW.
If certain facts are established, a judge or jury must assume another fact that the law recognizes as a logical conclusion from the proof that has been introduced. A presumption differs from an inference, which is a conclusion that a judge or jury may draw from the proof of certain facts if such facts would lead a reasonable person of average intelligence to reach the same conclusion.
A conclusive presumption is one in which the proof of certain facts makes the existence of the assumed fact beyond dispute. The presumption cannot be rebutted or contradicted by evidence to the contrary. For example, a child younger than seven is presumed to be incapable of committing a felony. There are very few conclusive presumptions because they are considered to be a substantive rule of law, as opposed to a rule of evidence.
A rebuttable presumption is one that can be disproved by evidence to the contrary. The FEDERAL RULES OF EVIDENCE and most state rules are concerned only with rebuttable presumptions, not conclusive presumptions.