WASHINGTON (AP) - The Supreme Court ruled Monday that confessions obtained by federal authorities before a suspect's first court appearance may be inadmissible if more than six hours elapse between an arrest and a court date.

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," Hon. 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 29½ 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.

The Supreme Court set aside that ruling Monday and ordered lower courts to examine whether the confession was given during the first six hours after arrest. If it came later, Souter said, courts must throw out the confession if they find that the delay in taking the prisoner to court was "unreasonable or unnecessary."

Hon. Stephen Breyer, Hon. Ruth Bader Ginsburg, Hon. Anthony Kennedy and Hon. John Paul Stevens voted with Souter.

In dissent, Hon. Samuel Alito said confessions that are voluntarily given should be admitted into evidence regardless of the time that passes before a prisoner first goes to court.

Alito said concerns about coerced confessions have largely been dealt with by Miranda warnings, which officers give at the time of an arrest by informing suspects of their right not to answer questions and obtain a lawyer's help.

Chief Justice Hon. John Roberts, Hon. Antonin Scalia and Hon. Clarence Thomas joined Alito's dissent.

The case is Corley v. U.S., 07-10441.