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Relevance—The Fundamental Concept in the Analysis of Evidence

September 4, 2018

Relevance is important in the analysis of the admissibility of evidence for obvious reasons. But whether a particular piece of evidence is relevant is important to the analysis of evidence on an even more fundamental level than often gets discussed—its “role” in the structure of evidence analysis. In fact, the fundamental concept—the starting point—in all analysis of the admissibility of evidence in American courts is found in the first four words of Rule 402 of the Federal Rules of Evidence:

Relevant evidence is admissible . . .

. . . and its converse from the last sentence of Rule 402:

Irrelevant evidence is not admissible.

Before I go on to explain in more depth what that “role” is, let me prove the point that this is the fundamental concept of the analysis of the admissibility of evidence. Here are the first two sentences of the official “Notes” to Rule 402 written by the Federal Rules of Evidence Advisory Committee when the Federal Rules of Evidence were adopted in 1975:

The provisions that all relevant evidence is admissible, with certain exceptions, and that evidence which is not relevant is not admissible are “a presupposition involved in the very conception of a rational system of evidence.” Thayer, Preliminary Treatise on Evidence 264 (1898). They constitute the foundation upon which the structure of admission and exclusion rests.

You will observe from reading this “Note” that this “fundamental concept” is not new with the adoption of the Federal Rules, but has been “a presupposition involved in the very conception of a rational system of evidence” since at least 1898 when Harvard law professor James Bradley Thayer wrote about it.[1]

Let’s see what some others have had to say. Here is Professor Dale Nance,

The cornerstone of modern evidence law is relevance. Its rationalist tones may not engender the passion of notions like prejudice, due process, or even privilege. Yet its theoretical and practical importance cannot be denied. For example, the heart of the Federal Rules of Evidence, Rule 402, codifies the two fundamental principles of the common law of admissibility: the presumptive admissibility of relevant evidence and the inadmissibility of irrelevant evidence. Relevance is the threshold admissibility issue, applicable to every piece of evidence offered.

Dale A. Nance, Conditional Relevance Reinterpreted, 70 B.U.L. Rev. 447 (1990).

As Professor Nance[2] explains, Rule 402 embodies the central concept upon which the Federal Rules of Evidence were based. If evidence is relevant, it’s presumptively admissible. With some minor exceptions, this is the only rule of evidence which “admits” evidence.

The rest of the rules serve two basic purposes.  Some rules explain the way trials and rulings on evidence work. For example, Rules 101, 103, 1008, and 1101 set forth the scope and applicability of the Rules; and Rule 104 gives us guidelines on how judges make decisions preliminary to rulings on evidence. The heart of the rest of the rules, however, serve the other purpose—to permit trial judges to “exclude” relevant evidence. That’s why the next words in Rule 402 are

. . . unless any of the following provides otherwise . . . .

The point of the authorities quoted above is that we never reach questions about character evidence, or hearsay, or opinion, or any of the other difficult concepts of evidence, if the evidence is not relevant. If the evidence is relevant, it’s admissible, “unless” some other rule or provision of law allows the trial judge to exclude it.

This “central concept” is fundamental to understanding how all of the other rules apply to the situations you face on a daily basis. I wrote a bit more about it in anther blog post, “Thinking Through the Structure of Evidence.” That one will be out shortly.

[1] Professor Thayer was one of the original scholars on evidence law, and his 1893 article on judicial restraint—“The Origin and Scope of the American Doctrine of Constitutional Law”— remains “one of the most renowned pieces of scholarship in American constitutional law.”  For a discussion of Thayer’s role in the development of modern evidence analysis, see

[2] Professor Nance is an internationally recognized evidence scholar who currently teaches at Case Western Reserve University. He previously taught at Cornell University, Chicago-Kent College of Law, the University of Colorado, and the University of San Diego.

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