John Henry Wigmore, who more than any other individual is responsible for the structure of the contemporary law of evidence in the U.S., favored a relevance standard that he sometimes called "legal relevance." Shortly after his death several several Evidence scholars (e.g., James, Trautman) argued that Wigmore had been wrong and that the appropriate relevance standard is "logical relevance."

Properly decomposed, Wigmore's legal relevance standard has two distinct ingredients: (i) the requirement that admissible evidence have more than a "bare minimum" of probative value, that admissible evidence have a "plus value," and (ii) the requirement that trial judges look to accumulated experience and precedent to determine the legal relevance of evidence.

The advocates of the logical relevance standard challenged both ingredients of Wigmore's legal relevance standard. First, they argued that logic compels the conclusion that evidence having any amount of probative value -- no matter how little -- is relevant for purposes of the law of evidence. Second, they argued that judges can and must ignore precedent when attempting to resolve disputes about the relevance of evidence.

In support of the first contention -- the contention that evidence having even the slightest amount of probative value must be deemed relevant --, the advocates of logical relevance argued that any rational trier of fact would consider any evidence that alters the probability of a legally-material fact to any degree. To impose any higher standard, they said, is to ignore the fact that a collection of individually-weak pieces of evidence can sum to a substantial amount, enough to satisfy any legally-mandated standard of proof and persuasion.

In support of their second contention -- their claim that experience and precedent have no bearing on disputes about the relevance of evidence --, the advocates of logical relevance appealed to Thayer's aphorism that "the law furnishes no test of relevancy" and they emphasized the uniqueness of each item of evidence.

• The advocates of logical relevance did not always distinguish between these two distinct ingredients of Wigmore's legal relevance principle. Moreover, they mischaracterized some features of Wigmore's approach. For example, Wigmore clearly distinguished between the question of the amount of probative required to make evidence legally relevant and the question of the "sufficiency" of evidence, the question of whether evidence establishes or can establish legally-material facts to the degree required by the applicable standard of proof. Furthermore, Wigmore clearly believed that judges must use logic (as well as experience and precedent) when assessing the (legal) relevance of evidence. But such scholarly misunderstandings are now probably of interest mainly to legal historians.

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1. Is the logical relevance standard mandated by logic? When was the last time that you encountered a legal rule whose content is dictated solely by logic? (A legal rule specifying the amount of probative value that an item of evidence must have to be characterized as "relevant" for legal purposes is a legal rule.)

2. Is it obvious that any real-world rational decision maker would or could consider all evidence having even the slightest amount of probative value? (Does some probative evidence produce more cognitive confusion than information?)

3. Does logic alone dictate that judges rather than jurors should resolve disputes about the relevance of evidence?

4. Part of the motivation for the logical relevance standard was a desire to preserve the role of the jury as the trier of fact. What is the difference between making a judgment about the relevance of evidence and making a judgment about its weight?

5. Can rational people differ in their judgment of the relevance of an item of evidence? If so, why should judges rather than jurors assess the relevance of evidence?

6. Are trial judges given the job of assessing relevance of evidence because judges are more rational than jurors? If so, does it follow that judges rather than jurors should be the trier of fact?

7. Now that the logical relevance principle is generally the governing legal standard (see, e.g., Note of Original Advisory Committee to Federal Rule of Evidence 401), is it true that trial judges (in jury trials) do not weigh evidence but leave that task exclusively to the jury? If so, how do you explain Federal Rule of Evidence 403? And how do you explain the power of judges to "take cases away from juries" because of insufficient evidence?

8. Is it true that every piece of evidence is different and that experience therefore has nothing to say about the probative value of evidence?

9. Can logic alone establish the probative value of any item of evidence?

10. Is it true that the law of evidence does not or should not make general judgments about the relevance or probative value of any type of evidence? If so, does it follow that the law of evidence does not or should not make general judgments about the probative value of the sexual inclinations or activities of alleged victims of sexual assault?