A learned treatise, in the law

Law

Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

 of evidence

Evidence (law)

The law of evidence encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence can be considered by the trier of fact in reaching its decision and, sometimes, the weight that may be given to that evidence...

, is a text that is sufficiently authoritiative in its field to be admissible as evidence in a court

Court

A court is a form of tribunal, often a governmental institution, with the authority to adjudicate legal disputes between parties and carry out the administration of justice in civil, criminal, and administrative matters in accordance with the rule of law...

 in support of the contentions made therein.

Under the common law

Common law

Common law is law developed by judges through decisions of courts and similar tribunals rather than through legislative statutes or executive branch action...

, such evidence was considered hearsay

Hearsay

Hearsay is information gathered by one person from another person concerning some event, condition, or thing of which the first person had no direct experience. When submitted as evidence, such statements are called hearsay evidence. As a legal term, "hearsay" can also have the narrower meaning of...

 - 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

Expert witness

An expert witness, professional witness or judicial expert is a witness, who by virtue of education, training, skill, or experience, is believed to have expertise and specialised knowledge in a particular subject beyond that of the average person, sufficient that others may officially and legally...

. There were four ways to introduce such evidence:

1. Adduce testimony that the opposing expert witness actually used that text to reach his conclusions;
2. Adduce testimony by the opposing expert admitting that the text is an authority in the field;
3. Have a friendly expert witness testifying against the opposing expert witness attest to the authoritativeness of the text.
4. Have the judge
   Judge
   A judge is a person who presides over court proceedings, either alone or as part of a panel of judges. The powers, functions, method of appointment, discipline, and training of judges vary widely across different jurisdictions. The judge is supposed to conduct the trial impartially and in an open...
   
    take judicial notice
   Judicial notice
   Judicial notice is a rule in the law of evidence that allows a fact to be introduced into evidence if the truth of that fact is so notorious or well known that it cannot be refuted. This is done upon the request of the party seeking to have the fact at issue determined by the court...
   
    of the text, if it sufficiently notable that the average person would know that it is an authority (for example, Gray's Anatomy
   Gray's Anatomy
   Gray's Anatomy is an English-language human anatomy textbook originally written by Henry Gray. The book is widely regarded as an extremely influential work on the subject, and has continued to be revised and republished from its initial publication in 1858 to the present day...
   
   ).

Under the Federal Rules of Evidence

Federal Rules of Evidence

The is a code of evidence law governing the admission of facts by which parties in the United States federal court system may prove their cases, both civil and criminal. The Rules were enacted in 1975, with subsequent amendments....

 803 (18), either party can introduce a learned treatise as evidence, irrespective of whether it is being used to rebut the opposing party. Such texts are now considered an exception to hearsay, with two limitations:

1. For the learned treatise to be introduced, there must be an expert witness on the stand;
2. Like a recorded recollection
   Recorded recollection
   A recorded recollection , in the law of evidence, is an exception to the hearsay rule which allows a witness to testify to the accuracy of a recording or documentation of their own out-of-court statement based on their recollection of the circumstances under which the statement was recorded or...
   
   , the actual learned treatise does not go to the jury, but instead comes into evidence only by being read to the jury.