Arias claims self-defense. Alexander attacked her because she dropped his camera while she was taking nude pictures of him, Arias says, and she grabbed a gun to fend him off.
To convict Arias of first-degree murder, prosecutors will have to prove she actually planned her attack.
The jury could also find her guilty of second-degree murder — which would mean she meant to kill Alexander but didn't plan it — or manslaughter, which would mean she didn't mean to kill him but was so reckless that she did.
Arias' self-defense argument, which would get her off completely, is tough to believe in light of how badly mutilated Alexander was. His back was reportedly covered in stab wounds, and he was nearly decapitated, though Arias says she has no memory of stabbing him. He was also shot in the head with a gun Arias says she recalls grabbing from his closet.
Prosecutor Juan Martinez pointed out that his stab wounds undermine her self-defense story.
“If he’s being stabbed in the back, would you acknowledge at that point that he’s no threat to you?” Martinez asked, according to the Associated Press.
It's hard to argue that Arias didn't mean to kill Alexander when she nearly cut his head off, and there's some evidence she planned to murder him.
Arias says she grabbed a gun from Alexander's closet, but previously told investigators that he didn't even own a gun to the best of her knowledge.
It's also possible that Arias stole a gun from her grandparents before she killed Alexander. A .25-caliber gun was reported stolen from their home just a few weeks before Alexander was shot with a .25-caliber gun, Reuters has reported.
Of course, the theft could be a coincidence. It's impossible to know for sure whether it was the same gun because Arias dumped the weapon in the desert after she killed Alexander.
If prosecutors manage to prove premeditation without a murder weapon, Arias could get the death penalty. It's unlikely Arias will be sentenced to death, however, in part because she's a woman. Since 1976, only a dozen women in the United States have been executed compared to more than 1,300 men.
The jury has also had an opportunity to watch Arias testify in her own defense for 18 days. She may not be the most likable defendant in history, but it could be tough for jurors to execute a 32-year-old they've come to know during a lengthy trial.
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