He said the PTSD test was merely one tool used to come to his diagnosis.
"I based the information primarily on my interviews, the crime scene photographs and descriptions, interviews with family members, police reports, emails, text messages and the psychological tests," Samuels said.
Martinez had also questioned Samuels' credibility, accusing him of blurring the line between objective observer and therapist when he bought Arias a self-help book about building self-esteem.
Samuels denied the accusation.
"Is there ever blurring of the lines between evaluator and therapist?" Willmott asked Wednesday.
"There should not be," Samuels replied, explaining that sending Arias the book is not considered therapy.
Trial adjourned early on Wednesday after a woman in the gallery vomited.
Samuels was set to return to the witness stand Thursday to answer questions from jurors that will be read aloud by the judge. Arizona is one of a few states where jurors have the right to query witnesses. In most other states, it's up to the judge to determine whether to allow it.
Alexander suffered nearly 30 knife wounds, was shot in the head and had his throat slit before Arias dragged his body into his shower.
Arias spent 18 days on the witness stand during which she described an abusive childhood, cheating boyfriends, dead-end jobs, a shocking sexual relationship with Alexander, and her contention that he had grown physically abusive in the months leading to his death.
She said she recalls Alexander attacking her in a fury. Arias 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 has acknowledged trying to clean the scene of the killing, dumping the gun in the desert and working on an alibi in an attempt to avoid suspicion. She said she was too scared and ashamed to tell the truth.
None of Arias' allegations of Alexander's violence, that he owned a gun and had sexual desires for boys, has been corroborated by witnesses or evidence. She has acknowledged lying repeatedly but insists she is telling the truth now.