The Supreme Court yesterday agreed to hear the case of a man who successfully challenged his murder conviction on grounds that his lawyer would not allow him to tell a lie on the witness stand in his defense.

Emmanuel Charles Whiteside was sentenced to 40 years in prison for the 1977 stabbing of another man in Cedar Rapids, Iowa, during an argument over drugs.

The case will bring the court into a longstanding and heated debate among lawyers about ethics and a lawyer's duty when his obligations to his client and to the court conflict.

States vary in telling lawyers what they should do when their clients lie. Some advise attorneys to tell the court what is happening; others advise lawyers to withdraw from the case but not reveal their reasons for doing so.

American Bar Association rules say "a lawyer shall not knowingly fail to disclose a material fact . . . when disclosure is necessary to avoid assisting a criminal or fraudulent act by the client."

In this case, the 8th U.S. Circuit Court of Appeals said that "the Constitution prevails over rules of professional ethics" and that Whiteside was denied his right to effective counsel when his lawyer prevented him from lying on the stand.

A week before trial, Whiteside told his lawyer that he would testify that he thought he saw a gun in the hand of the man he was convicted of killing. "If I don't say I saw a gun, I'm dead," his lawyer quoted him as saying.

Whiteside's court-appointed lawyer then threatened to testify against him. The appeals court said the lawyer's "commendable zeal to avoid deceiving the court" led the lawyer to become "an adversary to his own client." The court reversed the conviction.

Attorneys general of 37 states joined Iowa in asking the Supreme Court to overturn the ruling. The states argued that the appeals court ruling, if allowed to stand, could mean new appeals by convicts arguing that they were threatened by their lawyers and forced to tell the truth.

The case, to be argued this fall, is Nix v. Whiteside.