Is it okay to lie if it helps you to get something good? Most of us would probably answer no. Our common-sense morality tells us that, except in the most extreme cases, a good end doesn't justify using dishonest means.

But it turns out that for police and FBI officers, trickery is an accepted practice in questioning suspects. Interrogators can pressure suspects with clever lies--telling them that an accomplice has confessed, for example, or that an eyewitness saw them commit the crime, or that they've flunked a polygraph test--in their efforts to obtain a confession.

This darker side of interrogation surfaced a week ago when The Washington Post obtained a transcript of the FBI's interrogation of suspected nuclear spy Wen Ho Lee. FBI agents tried to convince Lee during a March 1999 interrogation that he had failed an earlier lie-detector test when, according to The Post's Vernon Loeb and Walter Pincus, "polygraph examiners actually had given him an extremely high score for honesty."

FBI agents also tried to browbeat Lee into making a confession--suggesting that if he didn't, he would die in the electric chair. "Do you know who the Rosenbergs are?" an FBI agent badgered Lee. "The Rosenbergs are the only people that never cooperated with the federal government in an espionage case. You know what happened to them? They electrocuted them, Wen Ho."

Tough tactics, but not all that uncommon. Courts have given police and the FBI surprisingly wide latitude in interrogation. The only clear limit is that you can't use techniques--such as physical torture or the psychological equivalent--that would compel an innocent person to confess to a crime he or she didn't commit. An example would be threatening a mother that she would lose her children if she didn't confess. Otherwise, lies are generally permissible.

The most widely used police manual advises that when cops are questioning someone they think is guilty, they should use tactics that "decrease the subject's perception of the consequences of confessing, while at the same time increasing the subject's internal anxiety associated with his deception."

Sometimes, that means trickery. Clever cops will sympathize with suspects, pretend to be their pals, agree with them that the crime wasn't really their fault. They will lie about the evidence they've collected, the witnesses they've got, the chance they can get the suspect a reduced sentence--whatever it takes to get a confession. Real life, it turns out, includes dialogue that would embarrass the screenwriters for "NYPD Blue."

Unfortunately, police trickery sometimes persuades innocent suspects to confess to crimes. A useful summary of such cases comes from recent law review articles by Margaret Paris and Welsh S. White, who are professors at the University of Oregon and the University of Pittsburgh, respectively. Some of these cases involved suspects who were mentally retarded, but other normal suspects were tricked or coerced into confessing to crimes they didn't commit.

A Connecticut man named Peter Reilly, for example, confessed to murdering his mother after police told him he had failed a polygraph exam. "The polygraph can never be wrong, because it's only a recording instrument, recording from you," the detective told Reilly. He then asked the 18-year-old suspect if he had any doubt he had hurt his mother:

"The test is giving me doubt right now," Reilly answered, and after many more hours of trickery and cajoling, he confessed. Evidence later proved that he couldn't have committed the crime because he wasn't home at the time.

A 1991 Arizona case shows how police trickery about evidence can persuade an innocent person to make a false confession. Questioning a murder suspect named Leo Bruce, police claimed they already had evidence of his involvement. "You are not here by accident and the deal is already cracked and there's already been statements taken and there's already been evidence matched up. . . . This is a serious deal, man, and we're not gonna go away."

After nearly 13 hours of interrogation--during which police showed him photographs of fingerprints and other supposedly incriminating evidence, and warned that if he didn't confess to at least a minor role in the crime, he might go to the gas chamber--Bruce confessed. "I just wanted it to end right there. I wanted to sleep. I was exhausted," Bruce said in explaining why he confessed to a crime he hadn't commited.

Cops and FBI agents use deceptive tactics every day in their effort to obtain the higher truth of a confession. They have a code of professional ethics that condones such lying, and so far, the U.S. Supreme Court--while never explicitly condoning police trickery--has, in effect, looked the other way.

But we should be wary whenever professional codes sanction behavior that we would otherwise reject. Journalists invoke professional ethics when they browbeat sources or invade people's privacy. Lawyers invoke professional ethics when they wink at lying by their clients. Cops invoke professional ethics when they lie to suspects.

It's all sanctioned, in theory, by the higher truth we're trying to achieve in our professional roles. But I'd be happier with more emphasis on ordinary truth, the kind we all try to practice in everyday life.