Joel Jacobsen

In Bonn I fell into conversation with a recent law graduate who was curious about legal studies in the States.  I described the classes I had taken the previous semester back in Chicago, including Evidence.  He looked puzzled.  "What's there to study about evidence?  Either it's relevant or it's not."  Until that moment I hadn't realized that the very concept of a "law of evidence" is an artifact of the Anglo-American legal system.

Justice Potter Stewart, whom I greatly admire, once wrote: "The basic purpose of a trial is the determination of truth."  If that were really the purpose of trial, we wouldn't need any rules of evidence other than the simple requirement of relevance.

For American lawyers, relevance is only the starting point. The other rules of evidence, the ones that take a full semester to study and years of practice to master, are almost exclusively concerned with ways to prevent the jury from learning information that is relevant to the decision they've been dragged out of their ordinary lives to make.

Or, to put the matter more bluntly, the basic purpose of the law of evidence is to prevent the determination of truth.

My Evidence teacher, the late Jon Waltz,  began the semester by asking students to explain the purpose of a trial.  One young woman gave the Potter Stewart answer, only to be laughed at from the podium.   (And I'm confident she remembers the scene with a smoldering resentment to this day.)  The "correct" answer, from Waltz's point of view, was that trials exist to resolve disputes.  Whether truth emerges is neither here nor there.

But I don't think Waltz's answer goes very far, either.  Keeping out relevant evidence doesn't necessarily make disputes any easier to resolve.  In some cases the censorship of reality might simplify matters, making it easier to fit the case into a pre-established category, but in others it will complicate them by excluding the one piece of information that would make sense of everything.

One of the most significant differences between the German civil law system and the Anglo-American common law system is the jury.  And that difference explains the law of evidence.  In American bench trials, the rules of evidence are only loosely enforced because it is assumed the judge, being a lawyer, will know enough to disregard inadmissible evidence.  The rules of evidence exist to prevent the jury from basing its decision on certain categories of evidence -- or, in other words, to prevent the jury from deciding for itself what evidence is reliable enough to base a verdict on.

The primal power struggle in any trial isn't between the prosecution and the accused, or the plaintiff and the defendant, but between the judge and the jury.  When the jury room door closes, jurors become the only courtroom actors beyond the direct control of the judge.  But while the judge can't control what comes out of the jury room, he can control what goes into it.  That's what the law of evidence is all about.