Dzhokhar Tsarnaev trial hears of Boston bombing fatal victims' final moments

Jurors in the Boston Marathon bombing trial heard poignant eyewitness testimony on Thursday about the final moments of the three people killed in the attacks, when twin bombs ripped through crowds at the race's finish line in 2013.

A father of three recalled watching people trying in vain to revive 8-year-old Martin Richard, one Boston police officer remembered administering CPR to 29-year-old Krystle Campbell and a second officer said she left the body of 23-year-old Lingzi Lu only when ordered to by her captain, amid fears there could be a third bomb.

Defendant Dzhokhar Tsarnaev, 21, has admitted through his attorneys that he and his older brother carried out the April 15, 2013, bombing that killed three people and injured 264. He is also on trial for the fatal shooting of a police officer three days later. But he has not changed his plea from not guilty, leaving it to a jury to convict him and, if they do, to determine whether to sentence him to death or life in prison without possibility of parole.

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Boston Police Department Officer Lauren Woods recalled running through crowds of terrified spectators before she helped some fellow first responders carry Lu, a Chinese exchange student badly injured in the blasts, into a waiting ambulance.

"A paramedic ... told us to take her off because she was gone and he needed to keep the ambulance available for people that they could save," said Woods, who stayed with Lu's body until her captain ordered her to leave.

"He said, 'No, you're alive, you need to go. She's part of the crime scene.'" Woods testified at U.S. District Court in Boston.

Tsarnaev faces a 30-count federal indictment on charges including two counts of use of a weapon of mass destruction resulting in death, and charges tied to the fatal shooting of a police officer three days after the attack, as the defendant and his 26-year-old brother, Tamerlan attempted to flee the city. The elder brother died later that night

The Tsarnaev family moved to the United States from Russia's restive Chechnya region about a decade before the attack. Prosecutors contend their actions were motivated by militant Islamic views.

Death penalty trials play out in two phases, with the jury first establishing whether the defendant is guilty and then, if the defendant is convicted, whether a death sentence is warranted.

Prosecutors and defense attorneys have argued during the first two days of the trial over what sort of evidence may be admitted during the first part of the trial.

Defense attorneys are trying to prove that Tamerlan Tsarnaev was the driving force behind the attack, with his younger brother playing a secondary role.

U.S. District Judge George O'Toole on Wednesday said he would accept only limited testimony about the older brother during the guilt phase of the trial.

On Thursday morning, defense lawyers challenged some of Wednesday's victim testimony, arguing that description of the surgeries more than a year after the attack were irrelevant to guilt.

O'Toole rejected that request as well, saying the testimony "did not go out of bounds."

'CHAOS'

On Thursday, Alan Hern, a father of three who had traveled to Boston from his home in Martinez, California, to watch his wife run told jurors he waited while bystanders administered first aid to his 11-year-old son, whose legs had been badly injured, and then loaded him into an ambulance.

"The last thing I did see was Martin Richard on the sidewalk, there were two people trying to revive him still, but I could see his eyes clearly and I didn't think he was alive," said Hern, a high school football coach.

Another Boston Police Officer, Frank Chiola, said he had been standing near the finish line when the first bomb went off and heard the second detonate as he was running to the scene.

"You couldn't tell who was alive, who was dead," said Chiola, who went on to perform CPR on 29-year-old Krystle Campbell, who also died. "It was chaos."

Another survivor on Thursday testified that he remembered being bumped by a person who he realized in retrospect was Tamerlan Tsarnaev. Jeff Bauman told jurors he later noticed the man had left a backpack in the crowd.

"He just looked very suspicious. He didn't look like anybody that was there. He wasn't having fun, he wasn't watching the race," said Bauman, who lost both legs. The next day, when he woke up in a hospital, Bauman said he immediately told a friend that he had spotted a suspect and worked with a police sketch artist.

"It was kind of a relief," Bauman said, "to know that I got to help out and do my part."