The questionable law enforcement techniques being employed by Kenneth Starr against President Clinton should be a cause of concern to all Americans, regardless of their politics or feelings about the President.

By threatening to prosecute Monica Lewinsky and her mother unless the former intern gives him the story he wants, Starr may well be encouraging Lewinsky to bend--or even break--the truth. Lewinsky knows that without transactional immunity, she could be prosecuted for past perjury, since her sworn affidavit is apparently different from what she said on the tapes. The President's lawyers do not have the power to rescue her from this jeopardy. Indeed, they cannot offer her anything--or even talk to her. Starr can offer her full immunity. But he will not do so unless her story is consistent with what he wants to prove.

Otherwise, he will prosecute her--though his mandate does not extend to alleged perjury committed in the course of a civil case unrelated to Whitewater. This kind of one-sided bargaining power gives Starr the strength of the legendary godfather to make an offer that cannot be refused. He can point to Susan McDougal as an example of someone who spurned his offer and is now languishing in prison.

Every experienced criminal lawyer knows what kind of testimony this brand of coercion can produce: a story tailored to secure the desired immunity without regard to whether that story is true, false or somewhere in between. The law books are filled with cases in which immunized witnesses lied because they believed that the prosecutor would given them immunity only in exchange for a story that helped him get a higher up.

I have had several clients who were tempted to stretch the truth in order to get a better deal. In at least one case, a client tried to invent an elaborate story against a public official in exchange for his freedom. Fortunately, when pressed by his lawyers, he admitted that the story was false and that he made it up because it was the only way he would save himself from imprisonment.

The risk that a prosecutor, like Kenneth Starr, could induce a false story from a frightened target is greatest when the allegations against the higher up are vague. Crimes such as "subornation of perjury" and "obstruction of justice" are as vague as they get. A slight shift in nuance or emphasis could turn the true reality of an innocent conversation or job offer into the false memory of an apparent felony. The shift in nuance need not even be deliberate. Memories tend to be enhanced by the realities of threat and promise.

If Kenneth Starr were really interested in getting at the truth, he would immediately give Monica Lewinsky transactional immunity without first requiring her to proffer an incriminating story against the President. He could then compel her to testify in front of the grand jury. If she testifies that the President did no wrong, the immunity would still protect her from being prosecuted for any past crimes, but if Starr could prove that she lied in front of the grand jury, the immunity would not protect her from perjury charges for that testimony. There is no valid reason, therefore, for Starr to demand a proffer which incriminates the President before he grants Lewinsky immunity. The only reason for this hardball tactic is to influence the content of what she will say.

If a defense lawyer were ever to try to influence the testimony of a witness by threats or promises, he would be prosecuted for obstruction of justice even if he coerced the witness to tell the truth. But prosecutors are not subject to the same rules.

Monica Lewinsky should be free to testify to the truth as she sees it, subject to the usual sanction of perjury, if it can be proved beyond a reasonable doubt that she deliberately lied after receiving the immunity. The content of her testimony should in no way be influenced by Starr's threats or promises. It is not Kenneth Starr who will be testifying. It is Monica Lewinsky, and Starr's heavy thumb should not be on the scales of truth.

Starr's defenders will surely argue that what he is doing--coercing incriminating testimony--is business as usual for prosecutors. That does not make it right, either against the President or an ordinary citizen.

The rules should be the same for prosecutors and defense attorneys: neither should be allowed to offer benefits or threaten harms in order to influence testimony. Imagine the irony if a witness in a criminal case were offered something far more valuable than a job--her freedom--in order to induce her to testify that she was offered a job in exchange for her testimony in a civil case.

Alan M. Dershowitz is Frankfurter Professor of Law.