Fidell told The Associated Press in an interview that Trump stated more recently in Las Vegas, Nevada, that five soldiers were killed trying to find Bergdahl. The Pentagon has said no one died in the searches.
Trump also has pledged to review the case if Bergdahl is not appropriately punished, Fidell said.
"I have no idea what Mr. Trump has in mind and I don't think Mr. Trump has any idea of what he has in mind," he said. "I think he's a big faker."
The lawyer criticized Sen. John McCain, the Republican chairman of the Senate Armed Services Committee, for saying his committee would investigate and hold a hearing if it disagrees with the outcome of the case.
Fidell also took issue with a 98-page report issued last week by the House Armed Services Committee that criticized the Obama administration's decision to swap the five former Taliban leaders for Bergdahl. The report said the committee would ensure that "Sgt. Bergdahl's behavior is adjudicated as required." Fidell said he read that as a call to "hammer" Bergdahl for his actions.
"Given this sort of barrage of vilification and now arm-twisting by the Senate and House Armed Services committees, which obviously wield tremendous influence over the military, I have to say that this is very troubling," Fidell said, adding that a pending court case is not the business of congressional committees.
The U.S. Army Forces Command charged Bergdahl on March 25 with "desertion with intent to shirk important or hazardous duty" and "misbehavior before the enemy by endangering the safety of a command, unit or place." If convicted, Bergdahl could get life in prison on the misbehavior charge and up to five years for desertion. He also could be dishonorably discharged, reduced in rank and made to forfeit all pay.
Fidell, a military justice expert who is also a visiting lecturer at Yale Law School, said a high-ranking officer charged with deciding whether evidence warrants a court-martial did not follow the advice of a preliminary hearing officer.
Lt. Col. Mark Visger had recommended that Bergdahl's case be referred to a special court-martial, which is viewed in layman's terms as a misdemeanor-level forum. That limits the maximum punishment to reduction in rank, a bad-conduct discharge and up to a year in prison.
"I had hoped the case would not go in this direction," Fidell said.
In announcing the decision Monday, the Army said a date for an arraignment hearing at Fort Bragg, North Carolina, will be announced later.
___
Associated Press writer Robert Burns and video producer Mathew Friedman contributed to this report.
