Adjudicative facts are simply the facts of the particular case. Legislative facts, on the other hand, are those which have relevance to legal reasoning and the lawmaking process, whether in the formulation of a legal principle or ruling by a judge or court or in the enactment of a legislative body. The terminology was coined by Professor Kenneth Davis in his article An Approach to Problems of Evidence in the Administrative Process, 55 Harv.L.Rev. 364, 404–407 (1942). The following discussion draws extensively upon his writings. In addition, see the same author’s Judicial Notice, 55 Colum.L. Rev. 945 (1955); Administrative Law Treatise, ch. 15 (1958); A System of Judicial Notice Based on Fairness and Convenience, in Perspectives of Law 69 (1964).
The usual method of establishing adjudicative facts in through the introduction of evidence, ordinarily consisting of the testimony of witnesses. If particular facts are outside of reasonable controversy, this process is dispensed with as unnecessary. A high degree of indisputability is the essential prerequisite.
Legislative facts are quite different. As Professor Davis says:
“My opinion is that judge-made law would stop growing if judges, in thinking about questions of law and policy, were forbidden to take into account the facts they believe, as distinguished from facts which are ‘clearly * * * within the domain of the indisputable.’ Facts most needed in thinking about difficult problems of law and policy have a way of being outside the domain of the clearly indisputable.” A System of Judicial Notice Based on Fairness and Convenience, supra, at 82.
An illustration is Hawkins v. United States, 358 U.S. 74, 79 S.Ct. 136, 3 L.Ed.2d 125 (1958), in which the Court refused to discard the common law rule that one spouse could not testify against the other, saying, “Adverse testimony given in criminal proceedings would, we think, be likely to destroy almost any marriage.” This conclusion has a large intermixture of fact, but the factual aspect is scarcely “indisputable.” See Hutchins and Slesinger, Some Observations on the Law of Evidence—Family Relations, 13 Minn.L.Rev. 675 (1929). If the destructive effect of the giving of adverse testimony by a spouse is not indisputable, should the Court have refrained from considering it in the absence of supporting evidence?