(CBS/AP) PHOENIX -- Jodi Arias' defense team introduced eight "mitigating circumstances" in a Phoenix courtroom Thursday, including her age, troubled upbringing and artistic talent, in an attempt to save the convicted killer from a death sentence.
The defense and prosecution delivered opening statements to jurors on whether Arias should get a life sentence or be executed as the case's penalty phase launched. The same jury convicted Arias of first-degree murder last week in the 2008 stabbing death of her lover, Travis Alexander.
"This isn't about excuses or justification," Kirk Nurmi, an attorney for Arias, told the jury. "But fairness and mercy come into play in your moral assessment of what the right thing to do is."
In Arizona, mitigating circumstances include "any aspect of the defendant's character, propensities or record and any of the circumstances of the offense." The defense also said Arias was a good friend, suffered abuse and neglect, tried to make the best of her life and improve herself, and had no previous criminal history.
Nurmi said witnesses including Arias' former boyfriend would take the stand in order to paint a picture of Arias' life before the crime and prior to her relationship with Alexander.
Arias herself would also speak, Nurmi said, "in a different way -- not about what happened, but about who she is."
"When you hear who Ms. Arias is, you will understand that life is the appropriate penalty," Nurmi said.
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.
"All of these items, every single one, is nothing more than the defendant's statements, an attempt to gain sympathy," Martinez said. "And in view of the fact that there are no mitigating circumstances in this case, based on what the jury instructions tell you to do, the only appropriate sentence is death."
Alexander's brother and sister also spoke to the jury, giving emotional victim impact statements. Steven Alexander, who described Travis as his "big brother," detailed the emotional and physical anguish he's suffered since losing his brother, including ulcers, a separation from his wife and nightmares.
"I don't want these nightmares anymore," he said. "I don't want to have to see my brother's murderer anymore."
Steven Alexander recalled the moments after he learned that his brother had been killed.
"I remember walking out my back door and screaming at the sky, asking why," Alexander said. "Then I sank down into a corner and I cried some more."
Crying, he read the jury a list of affirmations written by his slain brother for the year 2008, the year of his death. "2008 will be the best year of my life, in which I will lay the foreground for 2009 to dwarf the accomplishment of 2008," he read, recounting his brother's words. "This year will be the best year of my life, and I will succeed."
Travis Alexander's sister Samantha, sobbing as she read her statement, said her family's lives will "never be the same" following her brother's murder.
"Our minds are permanently stained with the images of our poor brother's throat slit from ear to ear," Samantha Alexander said. "To have Travis taken so barbarically is beyond any words we can find to express our horrific loss."
She described seeing her brother several weeks before his death, in May of 2008. During the visit, she said Travis was excited for her to read the introduction to the book he was writing.
The jury saw a picture of the siblings taken that day, with Travis' arm around his sister.
"He talked me into taking this picture even though I was in my PJ's," Samantha Alexander said. "It makes me cry every time I look at it. I'm so glad he made me take this picture. I will cherish it for the rest of my life."
Arias, wearing a black, short-sleeved shirt, cried during portions of the family's statements.
Once the penalty phase of the trial is over, the jury will deliberate again on Arias' sentence.
A unanimous decision for life in prison or the death penalty would not be a recommendation, but a binding sentence, Nurmi and the judge said. If jurors don't reach a unanimous agreement on the death penalty, the judge will sentence Arias to either the rest of her life in prison or life in prison with the possibility of release after 25 years.
"Make no doubt about it, as the judge said to you moments ago, the verdict you will render is not a recommendation," Nurmi said. "The judge is not free to disregard it...if you sentence her to death, she will stand at this podium and be sentenced by the judge to death."
Following the victim impact statements, the jury recessed for a noon break, and was set to return at 2 p.m.MST.