Jodi Arias was not on the witness stand on Thursday, March 14. She had testified in the Maricopa County court room for 18 days earlier in the trial and answered over 5, 500 questions during her first-degree murder trial for the 2008 Arizona killing of her ex-boyfriend Travis Alexander.

The 31-year-old is on trial for murdering her ex-lover, Alexander, a 30-year-old Mormon motivational speaker. Arias stabbed her victim over 27 times, slit his throat from ear to ear and shot him in the head. His body was discovered the day he was killed: June 4, 2008. Arias lied twice at first about how he was killed and later admitted that she killed him in an act of self-defense.

Arias' defense attorney Jennifer Willmot introduced Richard Samuels, a PhD psychologist onto the witness stand on Thursday. As a defense expert, Willmot testified about the conclusions he's drawn based on his therapy sessions with Arias. He had met with Arias 12 times over the course of three years. Samuels supported Arias' "foggy" memory issues she claimed is the reason why she cannot recall how and exactly when she stabbed her victim at least 27 times. 

Samuels said while Arias can remember killing Alexander, because she was in a state of acute stress, she may also have trouble remembering certain aspects of the crime she committed. He explained that Arias remaining silent about the sexual and emotional abuse she suffered during her on-and-off relationship wih Alexander, "is a classic symptom of an acute stress disorder." 

"She was not able to tell her family about what happened. She was not able to tell anybody about what happened," Samuels testified.

Samuels used a Powerpoint presentation, which prosecutor Martinez objected to many times on Thursday, with a diagram of a human brain. Samuels pointed out the part of the brains memory that is affected when stress occurs. 

Samuels also testified that Arias suffered from acute stress disorder, which only lasts a couple of months, but then  develops into Post Traumatic Stress Disorder. The psychologist learned this after he gave her two tests.   

Samuels cited a TIME article, Your Brain Under Fire, that states that "people who suffer from stress-inducing trauma frequently will not recall what happened for a certain period starting with the beginning of the trauma until sometime thereafter."

Willmott just brought up how Arias said she was in a "fog" during the attack and when she was driving out into the desert. Samuels said someone fleeing a scene seems to be able to function on automatic. So Samuels said in this "fog" people can even drive cars.

"Once a person enters this state, while the memories are not being formed, any activities that are involved in fleeing seem to be able to occur. Such as running away or getting into a car and driving away or getting on a horse and trotting away," said Samuels.

Samuels is explaining how amnesia can happen when someone experiences acute stress or have an acute stress disorder which is when someone experiences severe trauma that causes an individual great stress.

"Perpetrators of horrible crimes can also develop post traumatic stress disorder for having acted as the source of the crime," Samuels said.

Judge Sherry Stephens said an evidentiary hearing will be held on Friday, March 15  so Samuels can testify again without the jury present due to several objections by Martinez.

Testimony will resume on Monday.