Omar Khadr's Pentagon-appointed defence lawyer was taken to hospital by ambulance Thursday, after he collapsed just moments before the first day of the military commission trial in Guantanamo Bay was due to close.

The Canadian Press reports that Lt. Col. Jon Jackson, who is Khadr's only representation at the hearing, was cross-examining a witness when he asked the judge for a brief recess. He stepped away from the podium and collapsed.

A military spokesperson said Jackson, who recently underwent gall bladder surgery, was conscious when taken from the courthouse to hospital.

The deputy chief defence counsel with the Office of Military Commissions said late Thursday that Jackson might need to be flown to the U.S. for treatment.

"We don't know what his short-term prognosis is," Bryan Broyles told The Associated Press.

"He will not be in court Friday."

Jackson's unexpected departure just minutes before court was due to recess for the day brought a dramatic end to the opening day of Khadr's trial.

Opening statements paint contrasting pictures

The prosecution began its opening statements by calling the Toronto-born Khadr an al Qaeda-trained terrorist and murderer.

Prosecutor Jeff Groharing said the U.S. government will prove Khadr, 15 at the time of his alleged crimes, threw the grenade that killed an American soldier at a compound in Khost, Afghanistan.

Khadr boasted killing an American made him feel good, Groharing said in his opening statements.

"Omar Khadr is a terrorist who was trained by al Qaeda who murdered Sgt. 1st Class Christopher Speer," Groharing said, as the soldier's widow sat in court.

"Khadr decided to conspire with al Qaeda so that he could kill as many Americans as possible."

The prosecution said Khadr confessed to throwing the hand grenade that landed at the feet of Speer. He died eight days later from a shrapnel wound to the head.

Khadr's Pentagon-appointed lawyer countered that his client was only 15 at the time -- a scared, bleeding and blinded child who was not a war criminal and did not throw the deadly grenade.

Lt.-Col. Jackson emphasized Khadr was only in the compound the day of the July 2002 battle because his father, notorious al Qaeda financier Ahmed Khadr, sent him there.

"Ahmed Khadr hated his enemies more than he loved his son. He is a boy, with three other men who are bad men," Jackson said.

"He is scared. He is bleeding. He is blinded."

Jackson noted Khadr was already wounded by shrapnel to the eye and cowered in the compound as a fierce gunbattle took place, after hours of aerial bombings.

Jackson said Khadr has been waiting eight years to tell his story and the defence will show Khadr's confessions were only made because of threats of torture.

Khadr's American interrogator told him about an Afghan kid who was gang-raped by "four big black guys," possibly to death, while in custody, Jackson said.

"That is not just some story," Jackson said. "This is someone who is in the control of the United States army and he is scared to death."

Prosecution calls first witness

The first prosecution witness, the commanding officer of the battle identified only as Col. W, testified that he discovered Speers in the rubble of the bombarded compound.

"I held his hand for a minute. I noticed his eyes were not focused. He was mumbling incoherently. I tried talking to him, tell him things were OK, ask him to hold on," W said.

W also described seeing Khadr there, with two large gaping wounds in the upper area of his chest.

"He was mumbling," W said, noting that three others were lying dead nearby.

Col. W told the court that Khadr's condition appeared so grave he reported the alledged grenade-thrower died of his wounds. He changed his report two years later, after he was contacted by prosecutors preparing their case against Khadr.

The prosecution only needs to convince five out of the seven jurors – all U.S. military officers – to convict Khadr.

Reporting from Guantanamo Bay, CTV's Daniele Hamamdjian said Speer's widow sat mostly stoned faced in court.

"At times, she was emotional, specifically when the prosecution was talking about her deceased husband (and) she was in direct view of the jury, right behind the prosecution," she told CTV News Channel.

Charges against Khadr include spying, supporting terrorism and murder. He has pleaded not guilty on all counts.

The trial is expected to take several weeks.

The controversial system of war-crimes trials, known as military commissions, was established during the previous administration of George W. Bush. In response to critics, Obama revised the system to offer more protections to defendants. This is the first such trial during the Obama presidency.

With files from CTV's Daniele Hamamdjian, The Canadian Press and The Associated Press