Krystle Marie Campbell was the center of her family's attention, the social one who organized surprise birthday parties, went dancing with her brother, took her mother on a girls' night out.
"She never left the house without giving me a hug, and I miss that," William Campbell Jr. told the jurors who will decide the fate of Boston Marathon bomber Dzhokhar Tsarnaev, convicted earlier this month of killing Campbell's 29-year-old daughter and three others.
Campbell wiped away tears as he testified, while several jurors did the same.
"She was the light of my life," he said.
Tuesday marked the first day of the sentencing phase in Tsarnaev's trial, in which jurors will decide whether he should be put to death or spend life in prison. The first phase of the two-part death penalty trial determined Tsarnaev's guilt, and Tuesday began prosecution testimony about the lasting impact his crimes had on those who were at the finish line on April 15, 2013, and their families. It was about the lives of the people Tsarnaev killed.
"You know how Krystle, Lingzi, Martin, and Sean died," Assistant US Attorney Nadine Pellegrini told jurors in her opening statement. "Now you need to know how they lived. You need to know and understand why their lives mattered."
The prosecution is seeking the death penalty. Tsarnaev's lawyers, who admitted at the beginning of the trial that he and his brother, Tamerlan, planned and carried out the bombings, are expected to argue that he should be spared from capital punishment.
William Richard, the father of 8-year-old Martin Richard, one of Tsarnaev's victims, was in the courtroom Tuesday, as was Liz Norden, whose two sons each lost a leg in the bombings.
Jurors also heard from survivors, who described their fear in the moments after the explosions, and their continuing pain and anguish.
Gillian Reny, a high school senior from Boston when the bombs went off, cried Tuesday as prosecutors played a video of the chaos after the explosions, and recalled the horror she felt when she saw her legs torn apart.
She was placed in a medically induced coma and was hospitalized for weeks. Nicole Gross, a physical trainer from North Carolina who came to Boston to watch her mother run the Marathon, recounted the feeling "of going in and out" after her right quad was blown open.
"I just remember laying there, completely alone," Gross told jurors. "I just screamed for somebody to help me, or save me."
Celeste Corcoran walked to the witness stand on two prosthetic legs, having lost both of her legs in the attack. She described the moments when she lay on the sidewalk on Boylston Street, her legs blown apart, thinking she would die.
Her thoughts then turned to her children, she testified, including her daughter Sydney, who was also injured. She decided she could not die.
Her husband, Kevin, remained by her side, brushing her hair from her face with his hand.
"He kept telling me he loved me, he wasn't going to leave me," said Corcoran, a hairdresser who attended the Marathon for the first time in 2013 to watch her sister race.
Krystle's older brother, William Campbell III, said he misses the times they would call each other just to talk.
"She was just the centerpiece; she could talk to everybody," he told jurors, as prosecutors showed the jury photos of the siblings when they were children. "Every day, we still think about her. Not a day goes by where she doesn't pop in your heard in some aspects."
Tsarnaev, who has shifted between fidgeting and seeming indifferent during the trial, showed no emotion during Tuesday's highly charged testimony.
The 21-year-old Tsarnaev was convicted of 30 counts, 17 of which carry the possibility of the death penalty.
Three people were killed in the bombings: Campbell, Richard, and Lingzi Lu, a 23-year-old Boston University graduate student.
Tsarnaev and his brother also shot and killed Sean Collier, an MIT police officer. Tamerlan was killed during confrontation with police in Watertown.
The younger Tsarnaev's lawyers, while admitting he took part in the crimes, have asked the jury to spare him from the death penalty, saying he was manipulated by a dominating, influential older brother, who they called the mastermind of the attacks.
Prosecutors say the brothers were equal players. In her opening statement Tuesday, Pellegrini told jurors that it did not matter how Tsarnaev was radicalized, or when: He crossed the line and carried out the attacks out of his own belief, placing a bomb right behind a group of children, she said.
The defense team did not deliver its opening statement Tuesday, deciding to present their statement when they put on their own evidence. The defense case could start as soon as Monday.
US District Judge George A. O'Toole Jr. told jurors that prosecutors will first present aggravating factors they say justify a death sentence: whether the crimes were planned, whether they were "heinous, cruel, and depraved," whether Tsarnaev knew they would result in death.
The defense team will then present mitigating factors to argue for a sentence of life in prison, and O'Toole told jurors they must decide with "careful, considered, and reasoned judgment."
Pellegrini told jurors that they will probably hear about Tsarnaev's dysfunctional family life, and they will hear stories of him at school events, dances, and at camp, but she argued, "nothing will explain his cruelty and his indifference."
She added: "Because the evidence has shown and will show that Dzhokhar Tsarnaev deliberately selected a glorious and famous international sporting event for its fame and for the vulnerability of its spectators; because he twisted the Marathon into something cruel and ugly for his own purpose, and because he took the Marathon and turned it into a political statement to bring attention to himself, to his own beliefs, and to others who would share those beliefs."
At the end of her statement, she showed jurors a photo of Tsarnaev in his holding cell on July 10, 2013, the day of his arraignment and less than three months after the bombing. He is flipping his middle finger at the camera in an apparent show of defiance.
"This is Dzhokhar Tsarnaev, unconcerned, unrepentant, and unchanged," she said. "Without remorse, he remains untouched by the grief and the loss that he caused. And without assistance, he remains the unrepentant killer that he is."