The prosecutor displayed family portraits as the siblings spoke, prompting Arias to break down in tears herself.
Sister Samantha Alexander became emotional as she described how their grandmother, who raised the victim, saw her health fail after the killing and died around the time of jury selection.
"Travis was the glue in our family," Samantha Alexander said. She also recalled her brother's charisma, sense of humor, insight and "huge smile."
"I thought my brother was bulletproof," Steven Alexander said. "I thought he was stronger than anyone. He couldn't be cut down or knocked down."
Meanwhile, defence lawyer Kirk Nurmi said Arias will testify as he listed several factors that the jury can consider in deciding to grant mercy, including her age, troubled upbringing, lack of criminal history before the killing, and even her skills as a talented artist.
Prosecutor Juan Martinez went through each factor and sought to turn the attention to the gruesome killing, asking what her age, background and art skills have to do with what happened the day Travis Alexander was stabbed nearly 30 times.
Other witnesses in the penalty phase will include Arias' friends and an ex-boyfriend who lived with her for several years in California.
Arias' attorneys earlier asked to step down from the case, but a judge denied the request.
Details about the motion were sealed, but legal experts said Arias complicated efforts for her defence when she gave an interview to Fox affiliate KSAZ minutes after her conviction, saying she preferred death over life in prison.
"I believe death is the ultimate freedom, and I'd rather have my freedom as soon as I can get it," Arias said.
During a closed-door meeting with the judge on Tuesday, Nurmi and Jennifer Willmott sought permission to withdraw from the case, according to court minutes released Thursday.
Los Angeles-area criminal defence lawyer Mark Geragos said Arias' attorneys have a conflict of interest with their efforts to keep their client off death row and Arias' assertion that she'd rather die for her crime.
"It's not highly unusual," he said. "There are cases where defendants make decisions that they're better off on death row, but that puts the lawyer in a conflicted position. You've got a duty as a lawyer to bring the conflict of interest to the courts and disclose it."
Added Phoenix criminal defence lawyer Julio Laboy: "It would be something I would do in my major felony cases if I found that a client was actually working against me and not working with her defence."
Arias cannot choose the death penalty. It's up to the jury to determine a sentence.
On Wednesday, the panel took less than three hours to determine that Arias should be eligible for death in the killing of her one-time lover after prosecutors proved the murder was especially cruel.
Arias, 32, acknowledged killing Travis Alexander at his suburban Phoenix home after a day of sex. She initially denied any involvement then later blamed the attack on masked intruders. Two years after her arrest, she settled on self-defence.
The victim suffered nearly 30 knife wounds in what prosecutors described as an attack fueled by jealous rage after Alexander wanted to end his affair with Arias and prepared to take a trip to Mexico with another woman.
- AP
