Video surfaces of Jodi Arias doing headstand during interrogation as murder trial continues

(CBS/AP) PHOENIX - In newly released interrogation video footage, accused murderer Jodi Arias is seen alone in a northern California interrogation room in 2008 seemingly unfazed by the fact that she is being questioned about murdering her boyfriend, Travis Alexander. The video, which is barred from being shown to jurors, shows Arias getting up from her chair, walking to the wall and doing a 20-second headstand minutes before being charged with murder on July 15, 2008.

PICTURES: Jodi Arias murder trial

Arias, who is currently on trial, 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.

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On Thursday it seemed apparent that jurors in Arias' murder trial paid close attention to an expert witness who diagnosed her with post-traumatic stress disorder and amnesia as many of the panel's questions focused on specific details of his evaluation and how he could come to any conclusions relying on Arias' repeated lies.

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.

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.

"Can acute stress occur if someone plans to kill versus defending themselves from danger?" the panel asked.

"Um, homicide is of a different nature," Samuels said before being cut off by an objection from the prosecutor.

"Possible but not probable," he continued.

The jury later asked if it is possible for a defendant to trick a psychologist into thinking they have PTSD.

Samuels said it was possible but unlikely, noting when a person is telling the truth their stories tend to change slightly as they are questioned repeatedly. He said Arias' intruder story remained exactly the same until she eventually said it was self-defense.

"It is my feeling that once the story changed (from intruders) she was essentially telling actually what happened," he said.

Defense attorney Jennifer Willmott later questioned Samuels.

"Is it rational for a person who was at a crime scene to leave evidence behind that they were at the crime scene?" Willmott asked.

"No," Samuels said.

"Well thought out?" she prodded.

"No," Samuels replied.

Prosecutor Juan Martinez seized on Samuel's credibility, accusing him of forming a relationship with Arias and being biased.

Samuels previously testified he had compassion for Arias.

In his typical dramatic fashion, Martinez displayed a page from the dictionary defining the word "compassion."

"A desire to alleviate someone's distress is an indication of sympathy isn't it?" Martinez yelled.

"According to Webster's," Samuels replied calmly.

"So you felt sorry for her," Martinez snapped back.

"No, I didn't, a sense of compassion," Samuels said.

Alexander suffered nearly 30 knife wounds, was shot in the head and had his throat slit. Arias' palm print was found in blood at the scene, along with her hair and nude photos of her and the victim from the day of the killing.

Arias said she recalls Alexander attacking her in a fury. She said she ran into his closet to retrieve a gun he kept on a shelf and fired in self-defense but has no memory of stabbing him.

She acknowledged trying to clean the scene, dumping the gun in the desert and working on an alibi to avoid suspicion.

None of Arias' allegations of Alexander's previous abuse, that he owned a gun and had sexual desires for boys has been corroborated.

Complete coverage of Jodi Arias on Crimesider