FORT BRAGG, N.C. — Army Sgt. Bowe Bergdahl, who deserted his post in Afghanistan and was held captive by the Taliban for five years, suffers from post-traumatic stress and will need a range of treatment for that and other disorders, a forensic psychiatrist testified Wednesday.

Charles Morgan, who has extensively studied prisoners of war, was called as a defense witness in the punishment hearing for Bergdahl, 31, who has pleaded guilty to charges of desertion and misbehavior before the enemy. He faces a potential life sentence.

Under questioning, Morgan said that the lack of control that prisoners face in confinement could aggravate symptoms of the post traumatic stress by reminding Bergdahl of his Taliban captivity. He was tortured and kept in isolation for much of the time he was held by the militants.

Defense attorneys are attempting to establish a case for leniency, calling witnesses Wednesday who have highlighted his struggles with mental health and who also talked about his work to rescue stray cats.

Prosecutors have called witnesses who highlighted the consequences of Bergdahl's decision to desert his combat outpost. Several servicemen who were seriously wounded in the manhunt to find Bergdahl testified about their injuries and the desperate all-hands manhunt to get him back.

Any punishment will be decided by the military judge presiding over the hearing, said Col. Jeffery Nance. Closing arguments in the case could come Thursday.

Morgan said Bergdahl suffered from a personality disorder even before he enlisted in the Army. The symptoms made him seem odd, eccentric and aloof.

People with the disorder, called schizotypal, also often indulge in grandiose fantasies or believe grand conspiracies about how the world works, he said. That "unique world view" might compel them to take action they are convinced is morally right, even if it isn't well grounded in reality.

Bergdahl has said he initially left the post because he had concerns about his command's leadership and wanted to bring those to the attention of top leaders. He had told fellow soldiers that he felt his unit’s tactics weren’t aggressive enough in pursuing the Taliban.

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"He's a smart guy," Morgan said, but can be painfully naive. Before he joined the Army he had traveled to France with plans to join the Foreign Legion, but seemed puzzled that people spoke French and had to ask at the airport when he arrived where to find the legion, Morgan said. He then needed help getting a return ticket home.

People with schizotypal can often have a range of interests and be curious about the world. Bergdahl's own interests ranged from ballet to guns. He mused about Socrates.

That existing disorder when he joined the Army made Bergdahl more susceptible to post-traumatic stress disorder from his captivity, Morgan said. Bergdahl may also have had PTSD before his ordeal in Afghanistan, Morgan added.

Morgan also described an odd and sometimes tense family upbringing in Idaho.

“Home life wasn’t always peaceful,” Morgan said. Bergdahl feared his father, who sometimes displayed a violent temper and would punch his fist through the walls.

As a boy Bergdahl would sometime hide when he heard his father's truck coming up the driveway. He described a feeling of panic when he realized he had not brought the lure that his father had told him to pack when they went fishing.

He was home-schooled and his mother had trouble trying to teach him to read.

He had trouble bonding with people but is attracted to helping animals, according to a witness allowed to testify by phone under an arrangement where she would not be identified by name. She runs an animal rescue shelter.

Bergdahl trapped feral cats and brought them to her shelter for care. She said Bergdahl had an "uncanny" bond with the cats. "He's almost like a cat whisperer," she said.

Morgan said that working with animals is good therapy for someone like Bergdahl, who has trouble trusting other people, particularly after his treatment in captivity where he was regularly beaten.

Animals are seen as innocent and "don't harbor ill will," he said.