It’s a federal crime–under the heading ”Bribery of public officials and witnesses”–to give or promise ”anything of value to any person, for or because of the testimony under oath given or to be given by such person . . . .”

Now this statute has been turned against federal prosecutors, whose ability to win convictions often depends on promising something of great value to their witnesses: freedom.

A Wichita (Kan.) lawyer named John V. Wachtel–reasoning from the premise that ”if I paid a witness for his testimony, I’d be sitting in jail”–reached an unorthodox conclusion: Prosecutors should not be allowed to pay witnesses either, whether in cash or in the coin of leniency.

So when his client Sonya Singleton was convicted of helping a cocaine ring launder money, Wachtel (who goes by Val) played a long shot: He appealed, mainly on the ground that the prosecution had violated the statute (Section 201(c)(2) of Title 18) by promising leniency to a key witness for his testimony against Singleton.

Much to Wachtel’s surprise, he won. In a resounding July 1 decision, a three-judge panel of the U.S. Court of Appeals for the 10th Circuit suppressed the testimony, reversed Singleton’s conviction and awarded her a new trial. If the decision stands, it could affect thousands of other cases, including that of Timothy McVeigh, whose conviction was based in part on the plea- bargained testimony of Michael Fortier, and whose appeal is to be heard by a panel including two of the same three judges.

The panel in the Singleton appeal held broadly that although the ”ingrained practice of buying testimony” has been used by federal prosecutors for decades, with the acquiescence of the courts, it has been illegal all along.

This has set off quite a sputtering among criminal law experts, especially those at the Justice Department, which plans to appeal. ”Nobody ever took this argument seriously before,” says one official. If the experts are right, the panel’s decision will eventually be overturned, either by the full nine-judge 10th Circuit or by the Supreme Court.

But it will have been a salutary exercise nonetheless. Debate over this decision will shine new light into one of the darkest corners of the law, the ethically dicey dealings that begin with threats of hard time and end with vulnerable witnesses saying what prosecutors want to hear.

”If this is an occasion for taking a jaundiced look at the quality and veracity of informant testimony, that wouldn’t be half-bad,” says Lawrence Robbins, a former federal prosecutor and assistant solicitor general, who’s now with the Washington office of Mayer, Brown & Platt. ”Particularly now that the sentencing guidelines and mandatory minimum sentences have dramatically reduced the roles both of negotiation and of judicial discretion, prosecutors have the wherewithal to apply tremendous pressure on informants, many of whose pasts do not give much comfort that they would shrink from twisting the truth to achieve a better deal.”

Although apparently unprecedented, Singleton v. U.S. cannot be dismissed as a case of some crazy judge going off on a weird toot or straining for a pretext to invalidate an especially smelly deal. This was a routine deal. And it was found illegal, unanimously, by appointees of three different Presidents: Chief Judge Stephanie K. Seymour, a Carter appointee whose name has appeared on lists of possible candidates for the Supreme Court; Judge David M. Ebel, a Reagan appointee who once clerked for Justice Byron R. White; and Judge Paul J. Kelly Jr., a Bush appointee.

Judge Kelly’s lengthy opinion for the panel begins with Supreme Court precedents mandating strict judicial enforcement of the ”plain language” of statutes even when the results do not seem to be what Congress had in mind when it passed them. By its terms, he says, this statute applies to everyone, including prosecutors; that makes perfect sense because ”if justice is perverted when a criminal defendant seeks to buy testimony from a witness, it is no less perverted when the government does so”; and a promise of leniency to a person facing prison time clearly has great ”value,” and thus presents at least ”as great a threat to a witness’s truthfulness as a cash payment.”

Even prosecutors who seek only the truth, Judge Kelly notes, may unwittingly subject witnesses to ”the temptation, even if unconscious, . . . to color or falsify one’s testimony” to please their paymasters.

The panel ruled that the exemptions from criminal laws that courts have recognized for law enforcement agents in the field–such as undercover agents who participate in drug deals– are not available to prosecutors presenting evidence in court. The judges also took a narrow view of laws authorizing prosecutors to seek leniency for plea-bargaining defendants who provide them with ”substantial assistance” by fingering others: ”A defendant can substantially assist an investigation or prosecution in myriad ways other than by testifying. Nor will our holding drastically alter the government’s present practices. The government may still make deals with accomplices for their assistance other than testimony, and it may still put accomplices on the stand; it simply may not attach any promise, offer, or gift to their testimony.”

Critics stress that whatever the internal logic of the Singleton opinion, it will come as a great surprise to Congress, which never hinted in the legislative history of the bribery- gratuity statutes that it meant to ban leniency-for-testimony deals.

”When something is so ingrained in practice, and nobody’s ever dreamed that the statute prohibits it, then I think it’s safe to say that the statute doesn’t prohibit it,” says Andrew Frey, who was once the Justice Department’s top criminal law expert and is now with the New York City office of Mayer, Brown & Platt.

Nor would abolishing leniency-for-testimony deals be good policy, says Frey: ”Certainly the Sammy Gravanos of the world”–informants against violent organized crime groups–”are not going to testify unless you have some pretty powerful inducements.” Frey adds that payments to witnesses by interested private parties are ”inherently suspect in a way that’s not true when it’s a prosecutor. That’s not to say that prosecutors don’t overreach; some do.”

The established safeguard against such overreaching is to require disclosure of prosecutors’ deals with witnesses, opening the way for defense lawyers to discredit the witnesses as paid liars. Does this level the playing field? Wachtel thinks not: ”Here in Kansas, any time the United States government wraps the flag around a reformed sinner and says, ‘We believe him,’ the jury believes him–no matter how well I cross-examine him.”

Be that as it may, professor Kate Stith of Yale Law School faults the Singleton decision as an exercise in futility, on the ground that prosecutors could find ample avenues to circumvent its ban on explicit leniency-for-testimony deals. ”If the court’s concern is that prosecutors are running around and getting witnesses to testify falsely–which I don’t think is happening–this is not going to stop it,” she says.

True. But while the Singleton rule would neither paralyze prosecutors nor purify them, it would reduce their leverage over plea-bargaining witnesses.

Under current practice, a prosecutor can wait until witnesses have finished testifying and then decide unilaterally whether they have performed well enough to earn their rewards. Under Singleton, the only proper recourse for a prosecutor dissatisfied with a witness’s testimony would be to bring a perjury prosecution and try to convince a jury that the witness had deliberately lied.

The Singleton rule would thus offset somewhat the large increase in prosecutorial power that Congress has engineered over the past 15 years by shifting to prosecutors much of the authority that judges once had to determine the sentences of both plea-bargaining witnesses and convicted defendants.

Would that be a bad thing? Perhaps so, when the witness is a Sammy Gravano. But what about a small-time drug courier? Or a financial fraud artist, like Susan McDougal? Or–asks Val Wachtel–a Monica Lewinsky? Should witness-suspects like these be subject (as they are now) to the same pressures that prosecutors may need to squeeze truthful testimony from Mafiosi?

As the government’s appeals unfold in the Singleton case, such long-festering questions should get some overdue judicial and public attention. If so, we will have a court-appointed counsel from Wichita to thank for it, along with three federal judges who dared to attack the way things have always been done.

Did they really think they could outlaw decades of prosecutorial practice without getting shot down on appeal? I doubt it. But if and when they do get shot down, it will not have been a mere judicial kamikaze mission. It will have been a judicial bank shot–and a daring one at that.