Omar Khadr made his first appearance before a U.S. military commission on Wednesday, after more than three years imprisonment.

There are more than 500 prisoners at the U.S. naval base at Guantanamo, Cuba, and Khadr is the only Canadian in the prison. He is also one of only nine prisoners accused of any crime.

Khadr is charged with murder for throwing a grenade that killed U.S. medic Christopher Speer in July 2002. The attack also wounded several other American soldiers, including Sgt. Layne Morris, who lost an eye.

Omar Khadr in 2002.

Fifteen years old when he was captured in Afghanistan, Khadr is now a young man, broad-shouldered, slim, with closely cropped hair and a beard. During his court appearance on Wednesday he wore a Roots sweatshirt and looked much like any other teen.

Khadr addressed presiding officer Colonel Robert Chester respectfully, at times in a voice so soft he had to be reminded several times to speak up.

He sat calmly with his hands folded in front as him as the military prosecutor read the charges against him: murder, attempted murder, aiding the enemy.

His defense team will challenge the legitimacy of the military commission process. It will argue that Khadr was legally and emotionally a child at the time he is alleged to have killed Speer.

Wednesday's session was a pre-trial hearing. Khadr's actual trial will not start for several months.

But before that happens Khadr has asked for an upgrade to his legal team. His court appointed military lawyer is a 31-year-old army captain John Meriman.

Meriman has no trial experience.

At one point Chester became so frustrated with Meriman, he dropped his head into his hands and rubbed both temples in dismay.

Khadr has requested that a senior military lawyer be added to his defence team, a request Chester seems inclined to facilitate.

One problem Chester had with Khadr was the Roots logo on his sweatshirt. He ordered his lawyer to buy him some other clothing before the hearing resumes.

The Khadr family is well known in Canada. All five Khadr children have been separately accused or investigated for alleged links to terrorism.

Their father, Ahmed Said Khadr, was killed in a gunbattle with Pakistani forces in 2003.