The Supreme Court spent an hour yesterday discussing this arcane legal question:

Should the request that a Tennessee man named Abu-Ali Abdur'Rahman placed before a U.S. District Court last year be considered a motion under Rule 60(b) of the Federal Rules of Civil Procedure, or a "second or successive" petition for habeas corpus?

Anyone who listened to the oral argument could be forgiven for wondering why the court had decided to take up the issue, because there was hardly a mention of why the answer matters: Abdur'Rahman's life depends on it.

Abdur'Rahman is a death-row inmate in Tennessee, convicted of murder and sentenced to death in 1987. He says he was the victim of a dishonest prosecutor who hid exculpatory evidence. No Tennessee nor federal court has ruled on the merits of that claim.

If Abdur'Rahman's filing in federal court was a Rule 60(b) motion, as his lawyers insist, then he could be entitled to such a hearing, which might lead to a reversal of his sentence. But if, as lower federal courts have ruled, it was a second or successive petition for habeas corpus -- that is, one that raises an issue another court has dealt with -- it would be forbidden under a 1996 federal law designed to streamline death-row litigation. The way to execution would be clear.

The case is one of many highly technical matters surrounding the death penalty spawned by the 1996 law and the Supreme Court's decisions interpreting it, as capital defense lawyers seek tiny holes in what has become a tight web of procedural rules that are largely unfavorable to death-row inmates.

In that sense, Abdur'Rahman's case is actually more typical of the Supreme Court's involvement in the death penalty drama than such high-profile cases as last year's ruling banning executions of the mentally retarded.

Abdur'Rahman's attorney, Columbia University law professor James S. Liebman, a foe of the death penalty, started yesterday's argument on the defensive. In a surprise move, the court had recently asked both sides in the case to supply briefs on a new procedural issue that signaled concern among the justices that, under the 1996 law, Abdur'Rahman may not have the right to bring his case to the Supreme Court after all.

Before Liebman even opened his mouth, Chief Justice William H. Rehnquist, long a believer that extended death-penalty appeals in federal court undermine the finality of state judgments, instructed him to address that point, and he seemed generally dissatisfied with Liebman's answers, asking why Abdur'Rahman had come to the Supreme Court rather than going first to a lower federal court for help.

Justice Sandra Day O'Connor seconded the point, prompting Liebman to offer a different argument with the remark, "If the belt doesn't work, let's go to the suspenders."

Tennessee Attorney General Paul G. Summers appeared confident in urging the court to dismiss the case, but ran into intense questioning by Justice John Paul Stevens.

Stevens, who is active at oral argument but rarely emotional, seemed energized by the case. He all but took over the hearing.

He noted that the key point in Abdur'Rahman's argument is that the District Court that rebuffed his request for a new hearing on his claim of prosecutorial misconduct was unaware of an obscure Tennessee law that permitted Abdur'Rahman's request. Abdur'Rahman's attorneys and the state's were also in the dark, he said.

Since the Tennessee Supreme Court clarified the law in a subsequent regulation, Stevens asked, why shouldn't Rule 60(b), a catchall provision designed to let courts correct serious mistakes, apply?

Summers insisted that the District Court's rejection of Abdur'Rahman's filing, on the basis that it was actually a repetitive habeas corpus petition, and a subsequent ruling by a federal appeals court backing the District Court, meant that Abdur'Rahman had had all the hearings he was entitled to.

But Stevens wasn't buying. "He's not asking for a second consideration of a claim; he's asking for consideration of a claim that's never been litigated," he said.

Other members of the court picked up on Stevens's theme. "You're saying he's just out of luck," Justice Stephen G. Breyer said to Summers.

"Yes, sir," Summers conceded.

"That seems terribly unfair," Breyer observed.

The case is Abdur'Rahman v. Bell, No. 01-9094. A decision is expected by July.

Abu-Ali Abdur'Rahman contends prosecutor concealed evidence.