ASHINGTON, April 21 — The Supreme Court agreed today to hear a death-row inmate's appeal in a case that has become a focus of concern over the administration of the death penalty in Texas, a state that has conducted more than a third of the executions in the country in the past 25 years.

The inmate, Delma Banks Jr., came within 10 minutes of execution last month when the Supreme Court granted him a temporary stay. The justices will hear the case in the fall and are unlikely to decide it before a year from now.

Mr. Banks is the longest-serving of more than 450 inmates on death row in Texas. He was convicted in 1980, at the age of 20, of killing a teenage co-worker at a Texarkana steak house.

The legal issues in his appeal include claims of prosecutorial misconduct and defense incompetence, both of which the court agreed to review. But the justices denied review on a separate claim of discrimination in the selection of the all-white jury that convicted him and sentenced him to death. Mr. Banks is black; the victim, Richard Whitehead, was white.

Mr. Banks has had 15 execution dates, and his case lay dormant for eight years at the Texas Court of Criminal Appeals. After losing his state-court appeals, he turned to the federal courts and won a writ of habeas corpus three years ago from the Federal District Court in Texarkana, which found his death sentence constitutionally invalid due to both the prosecution's suppression of important evidence and to a defense that fell below minimal standards at the sentencing phase of the trial.

Last August, however, the United States Court of Appeals for the Fifth Circuit, in New Orleans, overturned that ruling, finding that the suppressed evidence was not sufficiently important and that the defense should have uncovered it earlier. The legal representation, while legally inadequate, had not made a difference in the outcome of the case, the appeals court said.

The three judges on the appellate panel marked their 78-page opinion "not for publication," meaning that it was not to be cited as precedent or included in the ordinary databases of judicial opinions.

While "unpublished" opinions are common — too common, in the view of some critics of the practice — they are almost always reserved for straightforward rulings in cases of limited consequence. A dismissive disposition in a case of this magnitude is highly unusual, and possibly helped draw the Supreme Court's attention to the appeal.

Two months ago, in another Texas death penalty case, the Supreme Court was sharply critical of the Fifth Circuit for setting too high a barrier to inmates seeking to appeal in habeas corpus cases. The vote in that case, Miller-el v. Cockrell, was 8 to 1, with Justice Anthony M. Kennedy writing for the court that while federal judges should defer to findings made by state courts, "deference does not imply abandonment or abdication of judicial review."

So it is possible that the court's decision today to grant review in Banks v. Cockrell, No. 02-8286, reflects some justices' doubts that the Fifth Circuit is approaching its responsibilities properly.

Had the justices not granted the last-minute stay on March 12, Mr. Banks would have been the 300th person executed in Texas of 846 executions nationwide since the death penalty resumed in 1976. This year, there have been 26 executions in the country; Texas accounts for 12 of them.

A "friend of the court" brief filed at the Supreme Court on behalf of Mr. Banks by a group of former prosecutors and judges said that errors in his case "are typical of those that have undermined public confidence in the fairness of our capital punishment system." The group included John J. Gibbons, a former chief judge of the United States Court of Appeals for the Third Circuit, in Philadelphia, and William S. Sessions, the former F.B.I. director who had been a federal prosecutor and federal district judge in Texas.

There were no witnesses to the 1980 murder and Mr. Banks, who rejected a plea bargain, has maintained his innocence. The claim of innocence is not before the court, however. His lawyers at the NAACP Legal Defense and Educational Fund in New York are arguing that the prosecution wrongfully withheld information about the two central prosecution witnesses.

One, Robert Farr, was a paid government informant who gave the highly damaging testimony at the sentencing phase that Mr. Banks planned to commit armed robberies and thus posed a continuing danger to society. At the trial, he denied his status as a paid informant. The prosecutor did not contradict him, instead assuring the jury that his testimony had been entirely truthful.

The prosecution also failed to disclose a transcript of a pre-trial interview of its other main witness, Charles Cook, a convicted felon facing an arson charge, which indicated that he had been coached and rehearsed in his testimony.