The result of any legal action depends in large measure on chance. This cannot be said too often to a people drunk on the mythology of justice. Sometimes chance works justice. The ninety-year-old leaf burner evades incarceration because the letter-of-the-law prosecutor by shear chance bursts a tiny blood vessel in a key area of his brain at the critical moment, and forgets to subpoena the witnesses to the trial so the judge dismisses the case. Sometimes chance works injustice. A battered family, counting on the conviction of an abusive husband and father as their only escape route, sees him released because the trial judge, beset himself by an unexpected personal crisis, declares a mistrial. These things happen all the time. Chance lives around every turn on the twisty path of a case through the system, and chance is blind to justice.

Jurors are selected at random from among all of the voting-age citizens of the jurisdiction, and where a jurisdiction has more than one judge, cases are assigned among the judges at random.

Some cases are more predictable than others. A mass murderer may be faced with a mountain of evidence of his guilt. Of course, he will still take his case to trial, because no prosecutor is going to be offering him anything in exchange for pleading guilty. He has no real choice — except in Utah, as to the manner of his execution. His case could be tried to one hundred different juries in succession, with the same evidence and the same arguments presented, and almost all one hundred, maybe all one hundred, would return verdicts of guilty.

Most cases that go to trial are not so predictable. Cases that are predictable usually settle. If, in a garden-variety car accident case, both sides predict that the jury will find the defendant eighty per cent at fault and find the plaintiff’s damages to be fifty thousand dollars, a settlement agreement at the forty thousand dollar level will almost always emerge. Cases go to trial because smart, experienced trial lawyers — the best trial-predictors we’ve got — can’t agree on the likely verdict.

In some cases, any prediction must be a guess. Take a case of two colliding drivers each swearing on the Bible that he and only he had the green light, where there is no real corroboration either way but there are lots of details from which able lawyers can fashion arguments. If that case is tried to a hundred juries in succession, each trial exactly the same, probably about half the juries will find for the plaintiff and about half will find for the defendant. The only reason for these different results will be the identities of the jurors on each jury, all selected at random from the community, some with predilections favoring the plaintiff, others liking the cut of the defendant’s jib.

Usually, the presence of chance in our legal system doesn’t introduce any systematic bias in favor of the home team or the visitors. A case isn’t tried a hundred times. It is tried once, and the parties have to accept the result. If they don’t get justice, at least they get closure, and the chance to move on. That alone, for many, can be a pearl of great price.

Not so fast, there, Dr. Kevorkian. Your Michigan prosecutors can try the same case a hundred times against you. Except for the identity of the deceased, it is the same case every time. And there is never any real dispute as to the facts. The jurors aren’t being asked to decide what happened, but to apply the moral values of the community to an act on the boundary of legality, committed openly. Ideally, what do we do with such “test cases” on the borders of the law? We try one case to one jury. We let that jury speak for the community as best it can. We live with the result.

Assisted suicide is a moral issue with partisans on both sides. Prosecutors know that if they try the same case to one hundred juries, they will get at least a few convictions. This gives them a tremendous advantage because the penalties faced by the two sides for a failure in any one trial are so unequal. One conviction, even after fifty straight acquittals, puts Jack Kevorkian in prison and out of business. But the prosecutor who lost the fifty previous trials to Jack spent not one minute in jail, lost not a penny of salary, made lots of zealous new friends, some with deep pockets, and was perfectly free to roll the dice in trial number fifty-one, secure in the faith that even a blind squirrel finds a nutty jury sooner or later.

Obscenity trials are essentially the same thing. The facts are the same trial after trial. Set aside movies depicting nonconsensual activity — including sex with children, beasts, and unwilling adults — and one dirty movie is exactly the same as the next: Very consenting adults doing lots of kinky things to each other under bad lighting. The cases present a moral issue on which the community is divided. A prosecutor knows that if she tries a dozen cases, showing a dozen different movies to a dozen different juries, she’ll probably get at least one or two convictions by shear chance. And that is all she needs, because the penalties for defeat are far from equal. One obscenity conviction can put a video store out of business, costing tens of thousands of dollars, all told. The prosecutor who loses an obscenity trial, though, suffers only a little temporary embarrassment.

A prosecutor who brings a dozen obscenity cases against the same video store owner and loses three fourths of them has suffered nothing at all for her defeats, while her few victories have almost certainly bankrupted and imprisoned her quarry. But what has she really proven? First, that a minority of the community thinks dirty movies are patently offensive and appeal to their prurient interest, whatever that is.

More importantly, though, she has proven the worst thing about the presence of chance in all courts: Where a large power chooses to force a weaker opponent to fight the same battle a hundred times, under circumstances where defeat for the large power matters to it not one bit, but one or two defeats for the weaker opponent mean utter disaster, the large power can always win the war.

A lawyer who adopts this strategy for victory is a bully. He sees his office as a divine right to impose his moral preferences upon the people, the will of the majority of their juries be damned. In his self-centered war of attrition, he forgets that our system for justice is rooted in the consent of the governed, not in the power of the governors.