The military trial of the only Canadian held at the Guantanamo Bay military prison is set to begin Thursday, five years after Omar Khadr was captured in Afghanistan.

Lawyers for the 21-year-old are expected to focus their arguments on whether the U.S. Defence Department has the right to try him at the naval base on the eastern tip of Cuba.

Omar Khadr, seen in a 2002 file photo, at the age of 15.
(Canadian Press)

Khadr is accused of murder in the 2002 death of American medic Sgt. First Class Christopher J. Speer in Afghanistan. He is also charged with spying, conspiracy and supporting terrorism.

Khadr, who has been at Guantanamo for five years, was charged with murder three years after he was first detained, one of four prisoners at Guantanamo to face charges. More than 300 prisoners are being held at the base.

Prosecutors will try to convince U.S. Col. Peter Brownback, who is presiding over Khadr's tribunal, that the Canadian is an "unlawful enemy combatant," a designation required by Congress in order to move ahead with the case.

In June, Brownback dropped the charges against Khadr, saying he didn't have proper jurisdiction. Khadr had been officially classified as an "enemy combatant," but the military courts in Guantanamo only have jurisdiction to try "unlawful enemy combatants."

The Pentagon argued it was a technicality and appealed the decision. In September, a U.S. military appeal court overruled the earlier decision and the charges against Khadr were reinstated.

A courtroom sketch shows Khadr, far left, in June 2007.
(Associated Press/Janet Hamlin, Pool)

Human rights groups argue that the Guantanamo military courts are illegal because they do not offer the same protections as U.S. courts.

Khadr's defence lawyers have complained they cannot make arguments based on the U.S. Constitution or international law.

The Bush administration created the commissions following the 2002 invasion of Afghanistan, arguing that neither military courts martial nor U.S. civilian courts were appropriate for trying the Guantanamo detainees because much of the evidence would involve sensitive issues of national security.

In 2006, the U.S. Supreme Court declared the Guantanamo court system illegal, but Washington quickly established a new military tribunal system.

The top court is also hearing a new challenge to the tribunal system after a group of prisoners argued they should have the right to go before a U.S. federal court to appeal their indefinite confinements.

Canada has refused to get involved in the case. Countries like Britain and Australia have demanded their citizens be sent home to face justice.

Khadr, whose father was an associate of al-Qaeda leader Osama bin Laden, is the last prisoner from a Western country at Guantanamo.

A new courthouse is under construction at the Guantanamo Bay military prison, along with a $12-million tent city to house lawyers, officials and journalists attending commission trials.