But murder convictions in Canada carry a mandatory life sentence, which may enable the parole board to alter its normal practice, said David M. Paciocco, a law professor at the University of Ottawa. And because Mr. Khadr was 15 at the time of his arrest, special provisions of Canada’s prisoner-transfer laws related to murder convictions may apply, said Allan Manson, a professor of law at Queen’s University in Kingston, Ontario.  Even if Mr. Khadr is turned down on his first application, Professor Manson said, he is almost certain to be released after serving two-thirds of his sentence.  Mr. Khadr was captured in Afghanistan in 2002 after a firefight with American troops.  During that battle, an American sergeant, Christopher Speer, was killed by a grenade that Mr. Khadr was accused of throwing. A videotape found after the firefight was said to show Mr. Khadr making and planting roadside bombs.  Last week, Mr. Khadr, who was born in Toronto and comes from a Qaeda-linked family, pleaded guilty to all five charges against him, including murder in violation of the laws of war, spying and providing support to terrorism.  After his plea, a jury of seven military officers — who had not been told how long his maximum imprisonment would be under the plea agreement — spent several days hearing testimony about how to sentence him. Under tribunal rules, he would serve either the sentence imposed by the panel or the maximum time laid out in the plea agreement, whichever was shorter.  Prosecutors called Tabitha Speer, the widow of the Army sergeant killed by the grenade, who read letters from their children about their sadness at losing their father. The children were 3 and 9 months when their father died.  The defense, which argued for leniency because of Mr. Khadr’s youth, submitted evidence that he would probably attend a college in Edmonton, Alberta, after his release. Mr. Khadr also acknowledged responsibility for his acts and apologized to Ms. Speer.  Although prosecutors asked for a sentence of 25 years, the panel decided instead on a 40-year term. After the official sentence was announced, the judge disclosed Mr. Khadr’s eight-year plea agreement.  The judge also released the text of diplomatic notes exchanged by the United States and Canada over Mr. Khadr’s eligibility for eventual transfer.  In them, the United States said it would support his application to transfer after a year, and the Canadian government said it was “inclined to favorably consider Mr. Khadr’s application to be transferred to Canada to serve the remainder of his sentence.”  Both governments expressed doubt about whether the parole board in Canada — an independent agency— would release Mr. Khadr early, emphasizing “that eligibility for parole does not mean that the release will be granted.”  Ian Austen contributed reporting from Ottawa.  A version of this article appears in print on November 2, 2010, on Page A16 of the New York edition with the headline: Child Soldier For Al Qaeda Is Sentenced For War Crimes. Order Reprints| Today's Paper|Subscribe
Omar Khadr was sentenced to 40 years in custody for war crimes, but he might be released in fewer than three years, the Defense Department said.