The former chief military prosecutor at Guantanamo Bay said Thursday he would be a defense witness for the driver of Osama bin Laden, marking what is perhaps the most stunning turnaround at the first U.S. military tribunals since the World War II era.

Air Force Col. Morris Davis, once a passionate defender of the military commissions but who resigned last October over alleged political interference, told The Associated Press he has agreed to appear for the defense at an April hearing for Salim Ahmed Hamdan, whose lawyers are seeking to dismiss war-crimes charges against him.

"It is somewhat ironic," Davis conceded in a telephone interview from Washington.

At the pretrial hearing inside the U.S. military base in southeast Cuba, Hamdan's defense team plans to argue that the alleged political interference cited by Davis violates the Military Commissions Act, Hamdan's military lawyer, Navy Lt. Brian Mizer, told the AP.

Davis alleges, among other things, that Pentagon general counsel William Haynes said in August 2005 that any acquittals of terrorism suspects at Guantanamo would make the United States look bad, calling into question the fairness of the proceedings.

"He said 'We can't have acquittals, we've got to have convictions,"' Davis recalled.

A Pentagon spokesman, Navy Cmdr. Jeffrey Gordon, denied that Haynes made such a comment. Gordon also denied the former prosecutor's broader allegations of political interference, which he has repeated in newspaper opinion columns and in interviews in recent months.

If the judge rejects the motion to dismiss, Mizer said the defense will seek to remove two top officials in the military commissions system — legal adviser Air Force Brig. Gen. Thomas Hartmann and Convening Authority Susan Crawford — from participating in the Hamdan case. This would likely result in further delays to a trial that has been stalled by legal challenges.

It is not yet clear whether the Pentagon — which defends the commission system as fair — will allow Davis to testify. In December, two months after he resigned as the chief prosecutor for the Guantanamo war-crimes tribunals, the Defense Department barred Davis from appearing before a Senate Judiciary subcommittee.

The U.S. holds about 275 men at Guantanamo and plans to prosecute about 80 before military commissions. The Pentagon this month charged six detainees with murder and war crimes for the Sept. 11 terror attacks and said they could be executed if convicted.

Hamdan faces up to life in prison if the tribunal convicts him of conspiracy and supporting terrorism. His lawyers admit he was a driver for bin Laden, but say he had no significant role in planning or carrying out attacks against the U.S.

Davis, now head of the Air Force judiciary, said he firmly believes "there are some very bad men at Guantanamo and some of them deserve the death penalty." But he says civilian political appointees have improperly interfered with the work of military prosecutors.

"I think the rules are fair," he said. "I think the problem is having political appointees injected into the system. They are looking for a political outcome, not justice."

He alleges, for example, that senior officials pushed for a plea bargain in March 2007 for Australian David Hicks, allowing him to serve a nine-month sentence in his native country for aiding the Taliban.

Davis said the sentence was too lenient and was orchestrated to help Australian Prime Minister John Howard, who was under criticism domestically for his support of President Bush and U.S. policies.