It's been a long legal journey for Arias, 34, whom a jury found guilty last year of first-degree murder in the gruesome killing of ex-boyfriend Travis Alexander, 30.
This week's court proceeding in Arizona is a retrial of the penalty phase. In 2013, the same jury that convicted her became deadlocked later
on whether she should be executed for the 2008 murder of Alexander, who was stabbed 29 times, shot in the face and had his neck slit from ear to ear.
The impasse came when the jury voted 8-4 in favor of the death penalty for Arias, a source with knowledge of the jury's vote said at the time.
A death penalty requires a unanimous vote by the 12 jurors, and during the penalty retrial, a similar 12-0 vote will be required if Arias is to die by lethal injection, said Jerry Cobb, spokesman for the Maricopa County Attorney's Office.
During the retrial, if all 12 jurors can't vote for death, then Arias will be eligible for one of two life sentences: life without the possibility of release or life with the possibility of release after 25 calendar years, Cobb said.
That means Arias and her legal team will need to persuade only one of the 12 jurors to vote against the death penalty for her to be spared from execution, Cobb said.
Graphic testimony expected
The 12 jurors and eight alternates are expected to hear evidence for three to six weeks, Cobb said.
That testimony won't rehash whether Arias committed murder. That's already been decided.
Rather, the jury will hear evidence from the prosecution on why a death sentence is warranted and from the defense on how Arias' background and relationship with Alexander pose mitigations favoring a life sentence, Cobb said.
Nevertheless, the testimony is expected to be gruesome and grisly because prosecutors must show the murder was done in a "cruel, depraved or heinous" manner, among other factors, Cobb said.
"The state will be arguing and building on that theme," Cobb said.
Arias' legal team is arguing that life is "the appropriate penalty" for the convicted murderer for a number of reasons, according to court papers they filed this month.
Her legal team notes that Arias has no prior criminal history. She was only 27 when she killed Alexander and has since been remorseful, according to court papers. She also has a psychological makeup that "impaired her ability to cope with the tumultuous relationship she had with Mr. Alexander," court papers said.
No live telecast until verdict
Unlike the 2013 trial, the penalty retrial won't be televised live.
Rather, Judge Sherry Stephens, who will preside over the retrial as she did in the 2013 trial, has ruled that while TV cameras will be permitted in the retrial, no video can be aired until a verdict has been rendered.
The judge's decision came after the defense argued that live TV coverage would keep their witnesses from testifying.
The 2013 trial was sensational, attracting a media circus and a national audience riveted by themes of sex, violence and 18 days of testimony by Arias, who detailed what she called an abusive relationship with Alexander but claimed she remembered nothing of his killing.
The trial also featured phone sex conversations between Arias and her boyfriend as well as video of her interrogation by police.
The public also became fascinated with Arias because she took the stand in her defense. More recently, she sought to act as her own attorney in the penalty phase retrial and was initially granted permission in August. But Arias changed her mind in September.
During last year's trial, jurors and the public saw Arias on video making a number of declarations to police investigating the murder.
"I'm not a murderer," she told detectives. "If I killed Travis, I would beg for the death penalty."
The police video also showed her doing bizarre behavior when left alone in a police room: she began stretching and doing handstands.
In another police interview, Arias blamed Alexander's killing on intruders.
"They didn't discuss much, they just argued," Arias told a detective.
"About what?" the detective said.
"About whether or not to kill me."
"For what reason?"
"Because I'm a witness," Arias said on video.
Then came a moment of high courtroom drama: the packed gallery sat in stunned disbelief when Arias took the stand in her defense.
"Did you kill Travis Alexander on June 4th, 2008?" the attorney asked her.
"Yes, I did," she said.
"Um, the simple answer is that he attacked me, and I defended myself," Arias said.
But the jury didn't buy it and convicted her of first-degree murder.