Jurors question expert witness in Arias trial

Psychologist Richard Samuels, a defense witness, testified for a fifth day Thursday after telling jurors his diagnosis explains why Arias can't remember much from the day she killed her lover.

Arizona is one of a few states where jurors have a legal right to query witnesses through written questions read aloud by the judge. In most other states, it's up to the judge to determine whether to allow it.

Samuels answered more than 100 questions Thursday, and then was questioned by attorneys on both sides about his answers. He resumes testimony on Monday.

Many of the juror questions Thursday focused on Arias' lies, how Samuels could be sure she is telling the truth now, whether her memory loss could be fabricated and his opinions on premeditation.

"How can we be certain that your assessment of Ms. Arias is not based on her lies?" one juror question read.

"The diagnosis of PTSD is a function of an evaluation based upon my 35 years of experience in working with individuals with PTSD," Samuels replied, noting he can say with "all reasonable psychological probability" that she meets the criteria.

Arias faces a possible death sentence if convicted of first-degree murder in the June 2008 killing of Travis Alexander in his suburban Phoenix home. Authorities say she planned the attack on her lover in a jealous rage. Arias initially told authorities she had nothing to do with it then blamed it on masked intruders. Two years after her arrest, she said it was self-defense.

When Samuels initially began his evaluation, Arias was sticking to the intruder story.

Jurors asked if Samuels could be certain that Arias wasn't still lying about the day of the killing.

"Not with 100 percent certainty," he said. "Psychology is the science of behavior so we're seldom 100 percent sure."

Samuels testified previously that Arias was likely suffering from acute stress at the time of the killing, sending her body into a "fight or flight" mode to defend herself, which caused her brain to stop retaining memory.

The jury asked Thursday whether this scenario could occur even if this was a premeditated murder, as the prosecution contends.

"Is it possible? Yes. Is it probable? No," Samuels said.