TORONTO - Accused Canadian terrorist Omar Khadr could not have thrown a grenade that killed a U.S. soldier in Afghanistan in 2002 because he was buried under the rubble of a collapsed roof, his lawyer argued Friday.

The Globe and Mail reports a judge at the pre-trial hearings in Guantanamo Bay, Cuba, barred Khadr's lawyer from showing a photo that shows Khadr under the debris.

Defence lawyer, U.S. navy Lt.-Cmdr. Bill Kuebler, claimed it clearly refutes the government's version of events.

Khadr, the only Canadian citizen and westerner detained in Guantanamo Bay, is facing several charges before a military commissions court at the U.S. prison camp in Cuba.

The most serious charge is related to his alleged murder of a soldier during a firefight.

Khadr was 15 at the time.

A U.S. official present during the firefight previously testified he saw Khadr sitting upright facing away from him in such a position that he could have thrown the grenade over his shoulder.

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