Omar Khadr was only 15 years old when he threw a grenade in an Afghanistan firefight that killed an American soldier. Today, more than eight years later, jury selection begins in his military trial at Guantanamo Bay.

Khadr, a Canadian citizen, moved with his family to Afghanistan in the 1990s after which time his father pushed him and his brothers to join al Qaida. Following the firefight which killed Sergeant Christopher Speer, Khadr was captured by American forces in Afghanistan. He has remained at Guantanamo Bay prison facility awaiting trial since his capture.

Since his arrest, the case against Khadr has been dropped and reinstated numerous times amid legal challenges and political calculations surrounding military commissions at Guantanamo (see here, here, and here). Last week, the United States Supreme Court refused to delay the trial after his attorneys sought to have it put on hold while they challenged the constitutionality of the military tribunals at the US army base in Cuba.

Now, it appears that after years of traversing the American judicial system, Khadr is set to stand trial for his crimes. He is charged with, among other offenses, murder in violation of the laws of war. The case has been widely criticized by domestic and international human rights groups who say that Khadr was a "child soldier," and should not be prosecuted. But Khadr appears willing to accept responsibility for his actions. He has previously refused plea deals, telling prosecutors:

"I have been used too many times when I was a child, and that is why I am here, taking blame and paying for things I did not have a choice in doing but was told to do by elders."

On Monday, the court met for a final pre-trial hearing to receive Khadr's not guilty plea and to rule on a number of outstanding evidentiary issues. The military judge accepted his plea and ruled that confessions Khadr made to police after his capture be used against him during the trial. Defense attorneys argued that the confessions were coerced and unreliable.

Opening arguments are set for Wednesday in what will be the first military commission since President Obama took office.