Canadian Omar Khadr will likely be convicted of murder by a U.S. military tribunal even though there's no hard evidence he committed the crime, his U.S. lawyer told a parliamentary committee Tuesday.

Omar Khadr is shown in a 2002 file photo, at the age of 15, around the time he was captured by U.S. forces in Afghanistan. (Canadian Press)

Lt.-Cmdr. William Kuebler told the committee in Ottawa that his client's only hope of a fair trial is if he's repatriated to Canada to face criminal proceedings here.

Khadr, 21, is being held at the U.S. naval base in Guantanamo, Cuba, on charges that he killed a U.S. soldier with a hand grenade during a firefight in 2002.

He was 15 years old at the time but will be tried by the same rules as an adult at the U.S. military trial. Critics say that violates international law on the treatment of so-called child soldiers.

"There is almost no real evidence to support the proposition that Omar actually threw a hand grenade in July 2002 that killed a U.S. soldier," Kuebler told the committee.

"Omar will probably nonetheless be convicted of murder by the military commission for little more than having survived the firefight."

Believes Khadr will get life sentence

Kuebler told the committee members that the U.S. military tribunal is stacked against his client and designed to secure convictions.

"Given the prejudicial nature of these proceedings, I believe that he will receive a life sentence or something very close to it," said Kuebler.

Khadr is the last citizen of a Western democracy to be held at Guantanamo since other countries, including Britain and Australia, successfully appealed to the U.S. to repatriate their citizens.

Khadr's defence lawyer urged the Canadian government to change its mind and seek Khadr's return to Canada where he can be tried as a juvenile.

But Conservative MP Jason Kenny said there is no legal mechanism under which to bring Khadr back.

He described the U.S. military tribunal system as legal and was skeptical about bringing Khadr before the courts in Canada.

"He didn't commit a crime in Canada. He didn't kill a Canadian abroad. What would trigger any treatment of him under the Canadian justice system if he were to be transferred here?"

Kenney denied that the government is setting a double standard when asked about his role in securing Brenda Martin's return to Canada from a Mexican prison.

"It's not an analogous situation," Kenney said after the committee hearing. "Ms. Martin has been convicted of a crime in a foreign country following a judicial proceeding [and] we're now seeking her penal transfer. That's not true of Mr. Khadr."

Ottawa's distaste for case due to Khadr family

Kuebler attributed Ottawa's reluctance to get involved in the case with the unpopularity of the Khadr family and tried to put distance between the family and his client.

The late patriarch, Ahmed Said Khadr, was accused of being a founding member of al-Qaeda, while the mother, Mahah, once mused she'd rather raise her sons in Pakistan than have them exposed to drugs and homosexuals in Canada.

"Canadians are right to be offended by the public comments of Mahah" and their expressions of sympathies for "our common enemies," said Kuebler.

But Kuebler argued that's no reason to convict Omar on flimsy evidence.

"Ahmed Khadr is dead, and the son should not go on being punished for the sins of the father … Omar is not one of our enemies in the war on terror, he is a fellow victim."

At pre-trial proceedings in the U.S., evidence has been disclosed that raised doubts about the credibility of initial claims that Khadr tossed the grenade.

With files from the Canadian Press