A defence lawyer for a young Canadian terror suspect said Monday he has filed three motions to dismiss war-crimes charges against his client, arguing that "unlawful influence" by the government has tainted the military commissions.

The military lawyer for Omar Khadr, Navy Lt. Cmdr. William Kuebler, accused Pentagon attorneys of interfering in the commission's disclosure process by deliberately thwarting evidence that could help defend the 21-year-old detainee at trial.

Kuebler alleges the Pentagon urged interrogators at Guantanamo Bay to destroy handwritten notes in case they were called to testify about potentially harsh treatment of detainees.

Khadr's defence team also filed a motion to dismiss charges based on allegations that Air Force Brig. Gen. Thomas Hartmann, the legal adviser to the military commissions, applied "excessive interference" in the prosecution of cases, Kuebler told reporters in an email.

In May, a military judge barred Hartmann from participating in the case against Salim Hamdan -- whose war crimes trial went to the jury Monday -- because he aligned himself too closely with prosecutors.

Kuebler said the motion alleging improper influence by Hartmann is based largely on the testimony of Air Force Col. Morris Davis, the former chief military prosecutor at Guantanamo who resigned in October amid disagreements with his Pentagon superiors.

The final motion questions the integrity of the military commissions process after the Pentagon removed a judge, Col. Peter Brownback, earlier this year, Kuebler said.

Khadr's attorneys argue the timing of the May removal was suspicious because Brownback was resisting pressure to set a trial date and sided with Khadr in disputes over access to potential evidence.

The Pentagon has said Brownback was replaced because his service orders were expiring.

Air Force Maj. Gail Crawford, a spokeswoman for the Pentagon office overseeing the tribunals, said Monday it would be inappropriate to comment on the defence motions because they are pending before the court.

Khadr, the son of an alleged al Qaeda financier, is accused of hurling the grenade that killed Army Sgt. 1st Class Christopher Speer, a Special Forces commando, during a July 2002 firefight at an al Qaeda compound in Afghanistan.

He has been charged with war crimes and faces up to life in prison. His trial is scheduled for October.

Khadr's case drew attention last month after his defence team released video footage of the detainee being interrogated by Canadian officials at the U.S. prison in 2003, when he was 16.