The court said in a 5-4 decision that long delays before a suspect sees a judge can give the government too much leverage over someone who has been arrested.

"Federal agents would be free to question suspects for extended periods before bringing them out in the open, and we have always known what custodial secrecy leads to," Justice David Souter wrote in the majority opinion.

The prisoner in the case, Johnnie Corley, was arrested on suspicion of robbing a credit union in Norristown, Pa. The FBI agents who arrested him did not take him to court for his initial appearance for 29 1/2 hours, during which time they elicited a confession from Corley.

Under federal law and previous court decisions, confessions obtained within six hours of an arrest are presumed to be valid and may be used at trial. The question in Corley's case was what courts should do with confessions when there is a delay before the first court appearance.

The federal appeals court in Philadelphia said Corley's admission that he robbed the bank could be used against him, ruling that the confession was voluntary despite the delay.