A photograph and a U.S. soldier's testimony prove Canadian Omar Khadr could not have killed a U.S. soldier in a 2002 firefight in Afghanistan, the terror suspect's military-appointed lawyer said on Friday.

Khadr, who attended the pretrial hearing Friday at the U.S. detention centre in Guantanamo Bay, Cuba, is accused of killing a U.S. army medic with a hand grenade during a four-hour firefight at a suspected al-Qaeda compound.

Lt.-Cmdr. Bill Kuebler told the hearing that the photograph shows Khadr buried under the rubble of a collapsed building at the time the grenade that killed Sgt. Christopher Speer was thrown, proving he could not have thrown it.

The Globe and Mail reported that the Col. Patrick Parrish, the military judge in Khadr's case, barred Kuebler from showing the photograph to the media.

Kuebler said he wants the soldier who gave a similar account — identified in court documents only as "Soldier No. 2" — to testify at Khadr's Jan. 26 trial.

That account differs widely from another report from a soldier that says Khadr was sitting up and moving when the soldier, believing Khadr threw the grenade, shot him twice in the back.

Khadr, now 22, was 15 when he was wounded and captured before being sent to the controversial base at Guantanamo Bay to face a military tribunal on numerous charges, including murder and conspiring with al-Qaeda.

If convicted of the most serious charge against him, Khadr faces a maximum sentence of life in prison.

The commission's military prosecutors have disputed the defence's claims that Khadr, the only westerner remaining in detention in Guantanamo Bay, is a child soldier deserving leniency.

They also have said they will present definitive evidence showing Khadr threw the grenade that killed Speer, as well as videotape showing him planting roadside explosives in Afghanistan.

Khadr's trial is expected to be the first military commission held under the administration of U.S. president-elect Barack Obama, whose election has thrown the fate of the prison and the military commission into question.

The Democrat has called for the closure of the country's detention facility at Guantanamo Bay. He also has voiced opposition to the two-year-old law signed by President George W. Bush that allows the military commission to try those accused of war crimes.