Canadian Forces Capt. Robert Semrau is accused of killing a severely wounded insurgent during an encounter in Afghanistan's Helmand province in October 2008. (Sean Kilpatrick/Canadian Press)

The fate of a Canadian Forces captain charged with committing a battlefield murder in Afghanistan is now in the hands of a jury of his uniformed peers.

As the historic murder court martial entered its final phase, the four-member military panel began deliberations Saturday in the case of Capt. Robert Semrau, 36, charged with second-degree murder in the October 2008 shooting death of an injured Taliban fighter.

Military Judge Lt.-Col. Jean-Guy Perron took more than four hours to deliver his final instructions to the jury.

"It is not enough for you to find Capt. Semrau is probably guilty," Perron told jurors. "Likely guilt is not proof beyond a reasonable doubt."

Semrau never testified, and his lawyer presented no evidence in a trial that spanned four months. And Perron told the jury the accused man was under no obligation to do so.

Perron read 84 pages of legal instructions to guide deliberations. No one knows for certain when the panel will reach a verdict. Under law, their deliberations will remain forever secret.

The panel deliberated for about three hours on Saturday and will resume on Sunday morning.

Before beginning their task, the jurors asked Perron in a written question about Semrau's mental state, but the judge told them this issue was not raised during the trial. They were to restrict their deliberations to what was heard in court, he said.

The trial heard evidence that Semrau told fellow officers after the shooting that he simply wanted to put a wounded and dying enemy fighter out of his misery.

This dramatic legal-military saga began Oct. 19, 2008, on a dusty battlefield in the Taliban-infested Helmand province, just west of Kandahar, the province where most of Canada's soldiers are stationed.

Semrau was part of a team of Canadian Forces mentors to the Afghanistan National Army.

Following an intense firefight that pitted Canadian and Afghan forces against the Taliban, an insurgent lay on the verge of death. Semrau fired two rounds from his rifle into the dying man, the court heard.

An Afghan National Army captain, who was on the patrol with Semrau, testified the Taliban fighter was "98 per cent dead" when he was found.

The insurgent had been strafed by a U.S. helicopter gunship and witnesses described serious injuries, including a severed leg and a gaping hole in his abdomen.

Semrau faced two charges under the Criminal Code and two under the National Defence Act. The most serious is second-degree murder, which carries a mandatory life sentence with no parole eligibility for 10 years.

If the jury acquits him of second-degree murder, it will consider whether he is guilty of attempted murder.

Semrau is charged under the National Defence Act with behaving in a disgraceful manner and being negligent in performing his duty.

Based on Perron's instructions, the jury could acquit Semrau of the most serious charge — second-degree murder — if it finds a reasonable doubt that his decision to fire two rounds into a badly wounded insurgent actually contributed to his death.

"The fact that no body has been found is an important factor," Perron said, but he added that the prosecution does not have to provide a corpse to prove the offence.

Semrau's lawyer has argued the prosecution did not prove its case beyond a reasonable doubt. The prosecution has argued there was no doubt Semrau fired the fatal two rounds, and that the evidence shows he made self-incriminating statements.

Semrau is a married father of two girls and had a spotless record with the British and Canadian militaries.

He was joined in court by his wife, Amelie, and his older brother, Bill, who came from Western Canada.