She could face the death penalty if convicted in a case that has been cable news fodder for weeks with lurid stories of sex, lies and violence.
On Tuesday, Arias continued testifying about boyfriend after boyfriend before she met Alexander who cheated on her, lied to her, had alcohol problems and didn't treat her well. The defense claims Alexander, a successful businessman and motivational speaker, too, was abusive, both physically and mentally.
On Monday, Arias told jurors how she endured an abusive childhood at the hands of her parents and planned to commit suicide after she killed Alexander.
She has been laying out her life in painstaking detail, beginning with the day she killed her lover. Arias claims her parents abused her starting at the age of 7, and that numerous boyfriends cheated on her and lied to her, but because of her naivety, she stayed with them on and off throughout her teenage and young adult life.
"Did you kill Travis Alexander on June 4, 2008?" defense attorney Kirk Nurmi asked her on Monday.
"Yes I did," Arias replied softly. "He attacked me and I defended myself."
Arias' defense is attempting to build sympathy with jurors in hopes they won't convict her of first-degree murder, something that could potentially lead to a death sentence, by establishing a past littered with abuse, said California criminal defense lawyer Michael Cardoza, who has been following the trial.
"What they're doing is trying to elicit sympathy from the jury, to show, look at what this poor person had to go through throughout her life," Cardoza said.
It's a good technique, he said, but it could backfire if her testimony drags too long into the minutia of her life.
"They could start losing some jurors," Cardoza said. "They should really step it up and move it along because if jurors get bored, they could stop paying attention."
The trial began in early January with salacious details about a torrid romance between Arias and Alexander after they met at a conference in Las Vegas in late 2006. She claims they dated for about five months, then broke up but continued to see each other for sex up until the day of his death. She initially told police she knew nothing of the killing, then blamed it on masked intruders. She eventually admitted her involvement, but claimed self-defense.
She said she lied early in the investigation about not being at the scene of the killing because she planned to commit suicide and never have a trial.
"At the time, I had plans to commit suicide. So I was extremely confident that no jury would convict me because I didn't expect any of you to be here," Arias told jurors on Monday. "I planned to be dead."
She testified Tuesday about yet another boyfriend she had in early 2000 who also eventually cheated on her, but she noted he treated her kindly.
"Did he ever hit you?" Nurmi asked.
"No," Arias replied.
"Did he ever call you a whore?" Nurmi prodded.
"No," Arias said.
Throughout the trial, defense attorneys have depicted Alexander as a liar and a cheater who called Arias derogatory names and told her and other girlfriends that he was a devout Mormon saving sex for marriage, while in reality he was having sex with other women.
Prosecutors have portrayed Arias as a jealous ex-girlfriend who stalked him for months after their breakup until finally snapping and killing him.
Authorities said they found her hair and bloody palm print at the scene of the killing, along with time-stamped photographs on a memory card in a camera discovered inside Alexander's washing machine that place Arias there on the day he died. The photos included one of Arias nude on his bed, one of Alexander alive in the shower, then one of his body on the bathroom floor.
Defense attorneys have yet to explain why Arias apparently attempted to clean the scene, washing Alexander's bedding and the camera, and what happened to the weapons.
Authorities say Alexander was shot in the head with a .25 caliber gun, the same caliber Arias' grandparents reported stolen from their Northern California home about a week before the killing.