“This is supposed to be about finding the truth.”

That audacious declaration came from Judge Reggie Walton last week at the perjury and obstruction-of-justice trial of I. Lewis Libby Jr., who served as Vice President Cheney’s top aide between 2001 and 2005.

While mindful that it is unwise to cross a federal judge, especially one in whose courtroom I’ve been sitting on and off for the past month, I’m going to throw caution to the wind: Judge Walton is wrong.

Criminal trials in America are not really a search for truth.

As several commentators have pointed out, Mr. Libby’s trial has awkwardly attempted to dodge the central issue in the investigation that led to his indictment, namely who leaked to the press the identity of a CIA officer, Valerie Plame. Jurors have heard about the issue repeatedly. However, they have been told to disregard evidence that a former State Department official, Richard Armitage; a former White House press secretary, Ari Fleischer, and President Bush’s top political adviser, Karl Rove, were as culpable, if not more culpable, than Mr. Libby for any leaks.

Mr. Libby’s allies view the special prosecutor, Patrick Fitzgerald, as a modern-day Inspector Javert, pursuing picayune charges against a well-respected public servant while ignoring the broader truth about the origins of the leaks. Many of Mr. Fitzgerald’s backers clearly see the trial as an opportunity to extract a pound of flesh from the Bush administration for its allegedly cavalier approach to the Iraq War. That Mr. Armitage’s leaks were the first and led directly to Ms. Plame’s exposure seems to have caused little more than a murmur from those massing with fevered anticipation around Mr. Libby’s guillotine.

Yet, the disconnect between a trial and the truth is not unique to Mr. Libby’s case. A trial is more like a football game, or sometimes a street brawl, than an attempt to come as close as humanly possible to what happened in a particular situation. Both the prosecution and the defense want to win. In this adversarial system, truth is often an afterthought and sometimes a casualty.

This is most apparent through the long list of witnesses not called at the Libby trial. It includes Messrs. Cheney, Rove, and Armitage, as well as alleged recipients of leaks about Ms. Plame, such as David Gregory of NBC News and John Dickerson of Slate. Either side could have tried to call these witnesses. Neither side did.

And Mr. Libby, whose boss has hardly been a crusader for civil liberties, has asserted his constitutional right not to testify and not to face more questions from Mr. Fitzgerald. Fair enough, but not the way to produce the kind of comprehensive account that bends toward the truth.

Mr. Libby’s lead counsel, Theodore Wells Jr., acknowledged last week that his job is to get his client acquitted, not to flesh out the historical record. “There’s no box on the verdict sheet that says ‘innocent’ or ‘you didn’t tell the whole story.’ The box says ‘guilty’ or ‘not guilty,'” Mr. Wells observed while explaining his decision not to put Mr. Libby on the witness stand.

As in football, both sides put on an offense and a defense. Trials can be won or lost not just on whom your side calls, but on the witnesses and evidence you can prevent your opponent from introducing. For months before the trial begins, lawyers bicker over motions “in limine,” which usually seek to block jurors from hearing certain evidence. Lawyers usually cite “prejudice” or “confusion” as the reason for keeping jurors in the dark, but the goal of these motions is simple: “winning.”

Sometimes, arcane legal rules also stand in the way of the truth. Mr. Libby’s lawyers wanted to call an NBC reporter, Andrea Mitchell, to ask her to explain her statement on a CNBC program that Ms. Plame’s CIA affiliation was “widely known” among intelligence reporters before she was outed in a column by Robert Novak. Ms. Mitchell has since said she misspoke or misunderstood the question.

Even though broad circulation of Ms. Plame’s identity tends to support part of Mr. Libby’s defense, Judge Walton refused to allow the jury to hear Ms. Mitchell testify on that point because court rulings preclude calling a witness for the sole purpose of questioning her about an out-of-court statement. The disconnect with reality can have a real impact. In the Alice-in-Wonderland world of the courtroom, Mr. Wells will be free to suggest to the jury that Mr. Dickerson spread Mr. Fleischer’s tale about Ms. Plame all over Washington, circulating it so widely that Mr. Libby may have heard it, as he claims, from reporters. The jury has heard Mr. Fleischer’s account of telling Mr. Dickerson on a road in Uganda but will probably retire unaware that Mr. Dickerson has publicly denied this important aspect of Mr. Fleischer’s testimony.

Judge Walton does strike a blow for truth-seeking by allowing jurors to submit written questions for witnesses. When the two sides dance around an issue for their respective strategic reasons, jurors sometimes step into the breach.

When the defense got one of Mr. Libby’s deputies, John Hannah, to give an example of his boss’s memory problems, the prosecution brushed aside the point, perhaps to avoid drawing out an example that could bolster Mr. Libby’s defense. However, a juror honed in, asking if Mr. Libby’s memory issues ever prompted doubt about his effectiveness. “Never,” Mr. Hannah replied.

In most courtrooms, this exchange would never have happened, because few judges allow jurors to ask questions. The next logical step would be to allow jurors to call witnesses neither side has called. Judge Walton, a former deputy drug tsar under President George H.W. Bush, is probably not the man to make such a radical move.

Often, the best way to search for truth is to divorce it altogether from the quest for justice. South Africa and more than a dozen other countries have discovered this in setting up commissions to investigate grave abuses.

Mr. Libby’s trial will likely produce a verdict and may even do some justice, but in terms of divining the truth, it is deeply flawed.