Desertion is a very specific charge under U.S. military law. And there are crucial differences between civilian and military criminal justice that make Bergdahl's conviction, or even a trial, unlikely.
As former Judge Advocate General lawyer and South Texas College of Law professor Geoffrey Corn told Business Insider, in the U.S. military, a conviction for desertion requires very narrow criteria to be met. The prosecutor would have to prove beyond a reasonable doubt that Bergdahl "quit his unit with an intent to remain absent permanently - and he had to have that specific intent," Corn explained.
Corn believes that it would be difficult to prove either of these in Bergdahl's case. The Pentagon has never considered him a deserter, and didn't removed him from the army's roster. "The military has to process paperwork so that you can't get back pay and leave and so that the unit can get a replacement," Corn says of the bureaucratic process of designating a soldier a deserter. "According to the Pentagon there's no evidence he was ever dropped from the rolls."
An AWOL conviction only requires proof that a soldier left his unit without permission. But that would also be difficult to obtain, Victor Hansen, a former JAG officer and professor at the New England School of Law, told Business Insider. Prosecutors would have to interview members of Bergdahl's unit about events that happened five years ago. "It would be challenging because of the time that's elapsed to piece together all the circumstances of him leaving the unit," Hansen said.
Bergdahl is also insulated from prosecution by an important difference between the U.S.'s civilian and military criminal justice systems. Corn explained that in civilian life, a suspect is mirandized as soon as they are arrested, which means that statements made during any subsequent interrogations are admissible in court.
In the military, a suspect is mirandized only after there's reason to believe a crime has been committed. Bergdahl's debriefers - the officers who will question Bergdahl upon his return to the U.S. - could render much of the evidence they collect inadmissible depending on when and if they mirandize him.
Bergdahl can be mirandized only after debriefers suspect he's committed a crime, a protection that could greatly limit the amount of evidence a military prosecutor could legally be able to use against him. Bergdahl's lawyers could also claim that debreifers delayed mirandizing him in order to extract additional evidence - a claim that could be used to make the entire debrief process inadmissible in court.
And there's one remaining hurdle to a court martial. Courts martial are the responsibility of the commander of a soldier's unit. Barack Obama has already called Bergdahl a prisoner of war, and Bergdahl was never designated as a deserter or taken off of the army's rolls. In fact, Bergdahl was promoted to sergeant in absentia. And he was freed in exchange for five high-value Taliban detainees.
It's doubtful that there would be much desire to prosecute Bergdahl unless the evidence of desertion or aiding the enemy is overwhelming. An AWOL charge might not even be worth the trouble in a commander's mind, Corn thinks. "If it turns out he just wandered off, I'm not so sure there would be much of an appetite to court martial him," Corn says.
From a commander's perspective, there would also be challenges attached to administratively discharging Bergdahl - effectively firing him from the military, with his benefits revoked. "They can't do that without giving him notice and opportunity for a hearing," says Hansen.
Bergdahl's case is troubling for a number of soldiers he fought alongside. In the Daily Beast, Nathan Bradley Bethea reached the blunt conclusion that "Bergdahl was a deserter, and soldiers from his own unit died trying to track him down."
But the law isn't concerned with the morally unsatisfying dimensions of Bergdahl's story - the fact that soldiers were killed in attempts to free him, or that the U.S. paid what some believe to be an unacceptably steep price to secure his release, is irrelevant to the evidentiary and procedural questions that go into a criminal prosecution. Unless debriefers determine that there's far more to Bergdahl's story than has been reported publically, the only U.S. prisoner of war in the Afghan theater likely won't be facing criminal charges when he returns home.