Prosecutors called a retired F.B.I. agent this week to testify that the man who is accused of orchestrating the Sept. 11 attacks freely discussed the deadly hijacking plot during four days of questioning in January 2007.
In doing so, the former agent, Frank Pellegrino revealed that at the outset of the interrogation, the prisoner asked when he would see a lawyer.
Mr. Pellegrino said he brushed off the request and went on to obtain a confession during 12 to 13 hours of questioning at Guantánamo Bay.
The prisoner, Khalid Shaikh Mohammed, would not get to consult a lawyer for another 15 months. By then, prosecutors had issued capital charges against him, five years after his capture in Pakistan and after years in the C.I.A.’s clandestine prison network, the black sites, where he was tortured.
The disclosure presented the court with another issue to consider as it decides a central question in the long-running Sept. 11 case. After years of isolation that included being waterboarded 183 times and other torture, did Mr. Mohammed voluntarily confess at Guantánamo Bay, and can what he said be used at his eventual death-penalty trial?
Prosecutors argue that Mr. Mohammed voluntarily discussed his role as the mastermind of the attack by 19 men who hijacked the four planes that crashed, killing almost 3,000 people on Sept. 11, 2001. Defense lawyers contend that he was trained to confess in a program of C.I.A. torture.
It was the Bush administration’s policy to deny former C.I.A. prisoners access to lawyers until they were charged in military commissions, the hybrid military-civilian court system the administration set up to skirt certain constitutional questions.
To build their cases, military prosecutors had teams of federal agents question Mr. Mohammed and other suspects within months of their transfer from C.I.A. prisons in 2006. The idea was to get fresh confessions from the prisoners that were uncontaminated by the dirty work of the C.I.A. In a setback to the theory, an Army judge recently threw out one of those confessions in another case as derived from torture.
Mr. Pellegrino said he and his two partners in the interrogation treated Mr. Mohammed respectfully and described their interactions as cordial and nonconfrontational.
The F.B.I. agent said he broke the ice by saying he envied the laptop Mr. Mohammed had been using before he was captured in Pakistan in March 2003.
“Frank, if you join Al Qaeda, I can get you a good computer,” Mr. Mohammed replied, Mr. Pellegrino testified.
Prosecutors consider Mr. Pellegrino’s account of the interrogation the most important evidence against Mr. Mohammed.
Mr. Pellegrino devoted a decade of his 33-year career in counterterrorism to trying to track down Mr. Mohammed after the 1993 World Trade Center bombing. By the time the two men met in an interrogation room at Guantánamo, Mr. Pellegrino had already built a different case against him for a thwarted plot to hijack commercial aircraft in Southeast Asia.
“I’ve been preparing my whole life for a potential interview with Khalid Shaikh Mohammed,” he said.
Mr. Pellegrino said he told Mr. Mohammed that he was not interested in what the prisoner had told the C.I.A. during his detention from 2003 to 2006, and that he wanted to hear his story independently.
“I’m not agreeing with what was done,” Mr. Pellegrino testified.
But he said Mr. Mohammed was in charge of the length and content of their interview, and was granted a prayer break each day and water to drink. “When we went in to speak to him, we were very comfortable that he was speaking to us voluntarily, given every opportunity to walk away,” he said.
The prisoner was shackled to a bolt on the interrogation room floor by one or both ankles, and looked unharmed, Mr. Pellegrino said.
On questioning by Gary D. Sowards, Mr. Mohammed’s lawyer, Mr. Pellegrino said he was unaware at the time that Mr. Mohammed had previously been waterboarded and subjected to other violent interrogation techniques by the C.I.A. Even so, he testified Wednesday, he stood by his belief that Mr. Mohammed spoke to him voluntarily.
Notes of the interrogation showed that Mr. Mohammed described himself as “a slave” in the first hour of his F.B.I. interrogation in 2007.
In court, Mr. Pellegrino appeared surprised. But he acknowledged that it must have been said after he examined handwritten notes taken by a former F.B.I. analyst who took part in the interrogation.
He did recall that Mr. Mohammed explained the three targets of the Sept. 11 attacks: the Pentagon as a military symbol, the World Trade Center as an economic symbol and either the White House or the Capitol as a political symbol. Passengers aboard Flight 93 fought that group of hijackers, forcing it to crash in a field in Shanksville, Pa.
Two military prosecutors monitored the interrogation, which was not recorded or transcribed, according to testimony.
Mr. Pellegrino said that, in response to a question from the prisoner, he also told Mr. Mohammed that there were no Supreme Court decisions concerning Guantánamo Bay that involved his right to a lawyer.
In June 2004, the Supreme Court granted military prisoners at Guantánamo Bay access to lawyers to challenge their detention through habeas corpus petitions in federal court.
In anticipation of that decision, the Bush administration moved prisoners who had been held by the C.I.A. at Guantánamo to other secret C.I.A. prisons. By the time they were returned in September 2006, U.S. intelligence and legal authorities were designing a framework to first obtain “clean team” confessions from C.I.A. prisoners who President Bush wanted tried, then afterward give them lawyers.
James G. Connell III, the lawyer for Mr. Mohammed’s nephew, Ammar al-Baluchi, described Mr. Pellegrino’s account as a double violation of a prisoner’s right to a Miranda warning, the right against self-incrimination and right to a lawyer that every U.S. criminal suspect is constitutionally entitled to hear.
“A technical Miranda violation is a failure to advise,” he said. “It is another layer when a suspect asks for an attorney and they don’t honor it.”
The judge permitted Mr. Pellegrino to testify by video feed from a courtroom annex in Crystal City, Va., with a larger-than-life image of him beamed to a screen above the witness stand.