(Updates with testimony)
By Daniel Lovering
BOSTON, July 14 (Reuters) - An FBI agent who interrogated a friend of the accused Boston Marathon bomber testified on Monday that he had told the friend that the bomber's life was "effectively over."
Azamat Tazhayakov, 20, is the first of three friends of Dzhokhar Tsarnaev to face trial on charges of interfering with the investigation by going to the suspect's dorm room and removing a laptop and backpack containing empty fireworks casings three days after the April 15, 2013, attacks.
FBI special agent John Walker led a search of an apartment in New Bedford, Massachusetts, where Tazhayakov lived with fellow Kazakh exchange student Dias Kadyrbayev four days after the bombing attack that killed three people and injured 264.
Walker has said he was pursuing a lead that Tsarnaev was hiding out at the apartment, but the lead turned out to be false. At the time, the bureau was concerned that other conspirators may have been involved in the bombing plot. Tsarnaev's older brother, Tamerlan, also a suspect in the bombing, was killed hours earlier after a shootout with police.
On Monday, Walker testified he arrived at the apartment after perhaps more than 60 heavily armed law enforcement officials had ordered the roommates and a woman identified as Kadyrbayev's girlfriend out of the apartment through a loudspeaker.
Tazhayakov was sitting in the back of a police car, handcuffed, with his shirt removed because "my colleagues were concerned anyone exiting that apartment might be bearing explosives on their person," he said. Walker said he asked Tazhayakov about any possible threats in the apartment because his colleagues would be entering it.
"In an effort to elicit truthful info on an immediate basis, I told him Dzhokhar Tsarnaev's life was effectively over, whether he was still living or going away," Walker said as the second week of the trial got under way. "I told the defendant that the defendant's life did not need to be over."
He said Tazhayakov agreed to go with authorities to a state police barracks where he was questioned. Hours later, early the next morning, Walker said he recalled the defendant saying, "I'm beginning to think we're being held against our will."
"I told him he was entirely free to go, that there was a cab waiting out front," Walker said.
Tazhayakov's attorneys argued before the trial that their client's statements during that interview, which began April 19 and ran into the next morning, should not be admitted at trial because he had not believed he was free to go at the time.
Walker has said he interviewed Kadyrbayev and Tazhayakov, and a third person he described as Kadyrbayev's girlfriend.
Kadyrbayev and Tazhayakov, as well as Robel Phillipos of Cambridge, Massachusetts, have been charged with hindering the probe into the bombing attack.
Tazhayakov could face up to 25 years in prison if convicted of obstruction of justice and conspiracy. Kadyrbayev faces the same charges. Phillipos is accused of the lesser charge of lying to investigators. (Editing by Scott Malone and Doina Chiacu)