ASHINGTON, May 5 — The Supreme Court delivered an unusual rebuke to a Texas appeals court today by unanimously setting aside the murder conviction of a teenager whose confession, the justices found, was the product of an illegal arrest and should not have been introduced at his trial.

The decision, which gives Texas the chance to retry the defendant, Robert Kaupp, for the 1999 crime without introducing the confession, made no new law. Rather, the Supreme Court viewed the Texas Court of Appeals as having made such obvious errors in upholding the conviction that the justices overturned its decision in an unsigned opinion, without even bothering to hear arguments in the case.

Mr. Kaupp, who was then 17, was suspected of having taken part in the murder of a 14-year-old girl, but the Harris County Sheriff's Department lacked evidence to obtain a warrant for his arrest. Instead, six police officers went to his home in the middle of the night and, after his father allowed them in, roused him from his bed by shining a flashlight on him.

"We need to go and talk," one officer said, to which the teenager replied, "O.K." The officers then handcuffed him and took him to the police station, barefoot and in his underwear. There, after receiving his Miranda warnings, he implicated himself in the murder.

The Texas appeals court found that Mr. Kaupp's "O.K." indicated consent, and that consequently he was not under arrest at the time of his confession. He should have been aware that he was free to go, the Texas court said, because "a reasonable person" in his position "would not believe that being put in handcuffs was a significant restriction on his freedom of movement." The state court added that Mr. Kaupp "did not resist the use of handcuffs or act in a manner consistent with anything other than full cooperation."

The Supreme Court's response to this reasoning today in its seven-page opinion, Kaupp v. Texas, No. 02-5636, was scathing. It was "beyond cavil" that Mr. Kaupp had been arrested, and arrested unconstitutionally without either a warrant or probable cause, the court said.

Contrary to the the state court's view, the opinion said, "a group of police officers rousing an adolescent out of bed in the middle of the night with the words `we need to go and talk' presents no option but `to go.' "

"As for the lack of resistance," the court added, "failure to struggle with a cohort of deputy sheriffs is not a waiver of Fourth Amendment protection, which does not require the perversity of resisting arrest or assaulting a police officer."

While the opinion was unsigned, the tone resembled that of Justice John Paul Stevens. Although Mr. Kaupp received his Miranda warnings at the police station and waived his right to counsel before talking to the police, the court said, it is firmly established under the Supreme Court's precedents that Miranda warnings alone cannot erase the taint of an unconstitutional arrest.

The court said that in order to use the confession at a retrial, the prosecution would have to be able to show some "meaningful intervening event" between the illegal arrest and the confession. At the same time, the opinion made clear the court's strong doubt that the state could meet that burden. Mr. Kaupp is serving a 55-year sentence.

Although the practice was once fairly common, it is unusual for the current Supreme Court to rule summarily in favor of a defendant in a criminal case. In recent months, however, the court has appeared to be paying increased attention to criminal justice in Texas. The Texas courts have gained a national reputation for ruling almost reflexively against defendants, a fact that some death penalty experts point to as an explanation for the state's national lead in executions. Texas has accounted for more than one-third of all executions in the country over the past 25 years.

The Supreme Court ruled in favor of a Texas death-row inmate earlier this year, and last month agreed to review another Texas death-penalty case.

There were also these developments at the court today:

Disclosure

The court accepted a government appeal and agreed to decide whether four death-scene photographs from the suicide of Vincent W. Foster Jr., the deputy White House counsel who killed himself in 1993, must be disclosed in response to a private lawyer's Freedom of Information Act request.

The United States Court of Appeals for the Ninth Circuit, in San Francisco, upheld their release, rejecting claims by the independent counsel's office and by Mr. Foster's widow and sister that disclosure should be barred under an information act exemption for law enforcement records that, if disclosed, would "constitute an unwarranted invasion of personal privacy."

The federal appeals court here had earlier invoked that exemption in rejecting a disclosure request for the same photographs. The justices accepted the Ninth Circuit case, Office of Independent Counsel v. Favish, No. 02-954, to resolve the conflict over the proper interpretation of the exemption.

Checkpoint

The court accepted an appeal by the State of Illinois and agreed to decide the validity of a checkpoint that the police in Lombard, Ill., set up one week after a fatal hit-and-run accident, at the same location and time of day, in order to find possible witnesses. The checkpoint snared a man who was found to be driving while drunk.

In reversing the conviction of the driver, Robert S. Lidster, the Illinois Supreme Court held that the police lacked the "individualized suspicion" necessary to detain someone, even briefly, for a criminal investigation. The justices ruled three years ago that roadblocks could not be used for ordinary law enforcement purposes, but the state is arguing in Illinois v. Lidster, No. 02-1060, that this was an "informational checkpoint" of a sort not barred by the earlier ruling in Indianapolis v. Edmond.