The Importance of Technical Principles of Evidence

Decades ago the renowned administrative law scholar Kenneth Culp Davis began a campaign, which he continued until his death in 2003, for the elimination of "technical" rules of evidence -- such as the hearsay rule -- in administrative proceedings and in bench trials -- nonjury trials -- in ordinary courts. Davis' campaign met with some success -- though, in the end, not with as much success as some observers claim or Davis hoped -- in ridding administrative ajdudication of rules such as the hearsay rule, authentication, the best evidence rule, and similar rules. See John Henry Wigmore, 1 Evidence in Trials at Common Law Section 4c (P. Tillers rev. 1983). The challenge to technical evidence rules in bench trials was much less successful. Id. Section 4d. And now Hamdan has struck down, at least temporarily, the complete abandonment of technical evidence rules in military commission trials for the detainees at Guantanamo.

Opposition to the abandonment of technical rules of evidence in administrative adjudication and in other nonjury proceedings has sometimes been ascribed to the power of interest groups such as trial lawyers and regulated industries. However, as Hamdan and the experience with the Guantanamo commissions suggests, more than professional prejudice or interest group politics is necessary to explain the durability of technical rules of evidence such as the hearsay rule. It is true that the question of how the risk of factual error can be best minimized at an acceptable price is difficult to resolve, but what is not reasonably debatable is that the probative value of evidence and the risk of inaccurate factfinding are influenced, and often profoundly so, by matters such as the number of people through which a testimonial report is relayed before it reaches the trier of fact and by the availability or unavailability of good evidence about the authenticity of tangible things such as documents. A rule that triers of fact may consider all "reasonably probative" evidence does not address the question of how hearsay evidence should be handled or evaluated or the question of how risks of forgery should be mitigated. Even more plainly such a seemingly reasonable rule -- you are free to consider all probative evidence -- says nothing at all about how the risks of factual error attendant upon the manner which evidence is collected should be handled. Hamdan doesn't have any fancy theorizing about evidence and inference but the Court's opinion reflects sound instincts about evidence and inference, instincts that no one, including a member of the Supreme Court, should be ashamed of.