Boston Marathon bombing survivor Karen Brassard, second from left, arrives at federal court Thursday in Boston for the death penalty trial of Dzhokhar Tsarnaev. Tsarnaev is charged in the 2013 bombing that killed three and injured 260.

BOSTON — It didn’t take long for prosecutors in the Boston Marathon bombing trial to convey the sense of fear, pain and grief caused by the 2013 attack. They let victims do it for them.

On the first day of testimony Wednesday in the trial of Dzhokhar Tsarnaev, whose lawyer admitted he committed the crime, three women who suffered severe injuries described their memories of the blasts, their wounds and the terror they felt.

Two of them had to have their left legs amputated and all of them spoke in graphic detail. It gave the jury a glimpse of the kind of agonizing testimony they can expect to hear in the coming months.

Sydney Corcoran, 17 at the time of the bombings, told the jury how she and her parents went to the marathon on April 15, 2013, to see her aunt run the race for the first time.

She recalled happily waiting to see her aunt cross the finish line one minute, then being immersed in smoke the next. She said she passed out and when she regained consciousness, she was lying on her back and men were tying tourniquets to her thigh. “I was getting increasingly cold and I knew I was dying,” she said.

Corcoran’s femoral artery had been severed and she nearly bled to death on the pavement.

Later, in the hospital, a nurse told her she was going to wheel her mother into her room, but needed to warn her about something.

“Your mother doesn’t have her legs anymore,” Corcoran said the nurse told her “I just said, ‘I don’t care, I just want my Mom.”’

Rebekah Gregory, who had 17 surgeries on her leg before doctors amputated it in November, walked slowly to the witness stand on an artificial limb.

“I remember being thrown back, hoisted into the air,” said Gregory.

She said she looked down at her leg: “My bones were literally laying next to me on the sidewalk and blood was everywhere.”

Karen Rand McWatters, whose left leg had to be amputated, described how she watched Krystle Campbell, her close friend, die next to her.

Tsarnaev showed little reaction as the case unfolded. His lawyer flatly told the jury that the 21-year-old former college student committed the crime.

But in a strategy aimed at saving Tsarnaev from a death sentence, she said he had fallen under the influence of his now-dead older brother, Tamerlan.

Three people were killed and more than 260 hurt when two shrapnel-packed pressure-cooker bombs exploded.