Justice Department spokesman Dean Boyd said Thursday, "The rules of criminal procedure require the court to advise the defendant of his right to silence and his right to counsel during the initial appearance.'' Mr. Boyd said Magistrate Judge Marianne Bowler made it clear on Sunday, after the first sealed charges were filed in her court against Mr. Tsarnaev, 19 years old, that the hearing would be held the following day.

Federal rules require that defendants appear before a judge without unnecessary delay--usually defined as within one business day.

Judge Bowler convened the brief, makeshift court hearing in the hospital room about 16 hours after the complaint was filed. Her reading of the Miranda warning came as part of the formal presentation of charges to the suspect, an act that would normally take place in court.

Judge Bowler was the first government official to advise Mr. Tsarnaev of his right to remain silent after his capture Friday night, officials briefed on the matter said.

The judge first told the Justice Department on Saturday that she intended to read Mr. Tsarnaev his rights on Monday, according to people briefed on the discussions. One U.S. official said the judge cited the intense television coverage of the capture as one reason for initiating the criminal prosecution.

Through a court clerk, the judge declined to comment.