Arias, 32, has admitted killing ex-boyfriend Travis Alexander in 2008 and lying about it for nearly two years, but insists she killed him in self-defense and has no memory of stabbing and shooting him, ABC News reported.
On Monday, psychologist Richard Samuels said people sometimes remember bits and pieces after a traumatic event. The defense witness said Arias has been consistent regarding her memory in 12 interviews.
"According to research, the more intense the trauma, the more likely and more complete the amnesia," Samuels said.
In explaining different types of amnesia, Samuels said amnesia is not "a fake or made-up kind of experience. It's not as if amnesia can only be made up, as to cover something up."
The defense team sought Samuels' insight to demonstrate differences between premeditated murder crimes and heat-of-passion crimes, CNN Headline News said Monday.
Prosecutor Juan Martinez objected to Samuels' testimony, pointing out Samuels would have to define those differences, potentially confusing the jury. In court last Thursday, Martinez said Samuels cannot be allowed to muddle the jury's understanding of the terms with his own definitions.
The defense announced at the end of Monday's proceedings Samuels would not testify about his research on amnesia before the jury, conceding the point to the prosecution. CNN said Samuels' comments could have been helpful to Arias.