Learned treatise

A learned treatise, in the law of evidence, is a text that is sufficiently authoritative in its field to be admissible as evidence in a court in support of the contentions made therein.

Under the common law, such evidence was at one time considered hearsay - a statement made out of court being introduced to prove the truth of the statement - and was not admissible except to rebut the testimony of an opposing expert witness. There were four ways to introduce such evidence: