PERRY MASON never had the problems faced by real-life criminal lawyers. His clients were always innocent. Their stories were invariably true so Perry was able to spend his time ferreting out the real culprit and getting him into the crowd at the courtroom for the final dramatic confrontation. Outside the world of fantasy, however, attorneys frequently deal with clients who want to embellish an alibi or stretch the truth on the stand. Sometimes the accused will even tell his lawyer in advance that he intends to lie. An attorney is supposed to encourage a client to trust him, giving assurance that their conversations are confidential. What, then, are a lawyer's obligations when a client reveals his intention to commit perjury?

The answer, surprisingly, is not clear, but last week the Supreme Court heard argument in a case that may provide some guidelines. The appeal arose out of an Iowa drug killing. The accused, Emmanuel Charles Whiteside, told his court appointed attorney, Gary Robinson, that he intended to lie on the stand. Mr. Robinson counselled against this tactic, said he would not cooperate in presenting perjured testimony and threatened to disclose the facts to the judge and, if necessary, "impeach" his client's testimony. That was persuasive, and Mr. Whiteside did not tell the proposed lie; he was, though, convicted of second-degree murder. The U.S. Court of Appeals for the 8th Circuit ordered a new trial on the grounds that the accused had not received the effective assistance of counsel.

It will be hard for the Supreme Court to uphold this judgment without appearing to sanction a constitutional right to have a lawyer's assistance in preparing perjured testimony. Even if the justices believe Mr. Robinson was too vigorous in arguing with his client, they could still reverse on the grounds of harmless error since the proposed perjured testimony was not, in fact, presented at trial and Mr. Robinson ably defended his client in arguing self-defense.

It would be better, though, if the court gave some guidance to attorneys facing this problem on a regular basis. It is agreed that an attorney cannot cooperate in fabricating testimony or knowingly present false testimony by witnesses. But the accused has a right to testify in his own behalf. If an attorney believes his client intends to lie must he withdraw from the case? Should he tell the judge or even, after withdrawing, testify against the accused? Or should he simply let a client tell his own story on the grounds that it might possibly be true? What will it do to the attorney-client relationship -- constitutionally protected in a criminal case -- if an accused cannot talk to his advocate in complete confidence?

These questions are so important that bar associations in 37 states have filed briefs in the Whiteside appeal. For the legal profession, it could be one of the most important cases decided by the high court this term.