Former Taliban prisoner Sgt. Bowe Bergdahl has retained a civilian lawyer to represent him during the ongoing Army investigation into his disappearance in eastern Afghanistan in 2009.

Yale law professor Eugene Fidell, an expert in military law, said he met with Bergdahl in Texas last week and would be present when he is interviewed by Gen. Kenneth Dahl, who is leading the Army’s inquiry into the circumstances of the soldier’s disappearance and whether he intended to desert his unit.

Fidell said he is working in conjunction with an “interim” military lawyer who has been appointed to represent Bergdahl.

“It’s certainly a most unusual case,” said Fidell, who declined to comment on his meeting with Bergdhal. “It’s a case that anybody who has heard about it feels engaged and gripped by.”

Bergdahl, who was held prisoner for five years, some of it in a locked cage, was released six weeks ago in a controversial prisoner exchange with the Taliban. On Tuesday, military officials said he had completed his medical treatment at Ft. Sam Houston in San Antonio, Texas, and is now on “regular duty” and living with fellow soldiers on the base.

Army investigators were not able to interview Bergdahl until he had made that transition; the deadline for the inquiry is mid-August.

An earlier Army inquiry into Bergdahl’s disappearance found that he left his post without permission but did not answer the question of his intent.