A U.S. Army National Guardsman was sentenced Wednesday to life in prison with the chance of parole for the murder of an Afghan civilian.

Sgt. Derrick Miller of Hagerstown, Md., shook hands with several soldiers in his unit after the 10-member military jury delivered the sentence at Fort Campbell after two hours of deliberation. The 28-year-old was found guilty of premeditated murder.

His attorney had argued during two days of testimony that Miller acted in self-defense when he shot a man last September. The military has identified him as Atta Mohammed but his name was not used in court.

Defense attorney Charles Gittins told the jury that Miller stopped the man for questioning when he walked through a defensive perimeter that Miller's unit had set up around a mortar unit.

Gittins said Miller believed the man could be a threat to his unit and that during questioning the man tried to grab Miller's weapon.

Gittins told the military panel during closing arguments that if they believed Miller acted in self-defense, they must acquit him.

"You have Sgt. Miller's life in your hands," Gittins said.

But Spc. Charles Miller, an eyewitness and Guardsman from Maryland, testified he heard Sgt. Miller threatening to kill the man if he didn't tell the truth and then straddling the man, who was lying on his back, before shooting him in the head.

Prosecuting attorney Maj. Matt Calarco said during closing arguments, "Immediately following the event the accused said, 'I shot him. He was a liar.'"

The jury deliberated for less than three hours before finding Miller guilty.

Miller showed no reaction to the jury's decision to convict, but family members cried quietly in their seats.

Miller, a husband and father of two, was assigned to a Connecticut National Guard unit and attached to the 101st Airborne Division at the time of the shooting in Eastern Afghanistan. After joining the National Guard in 2006, Miller had three combat deployments and had recently been promoted, said Capt. Michael Tregle, one of his two attorneys.

"Derrick Miller made a bad decision, but he deserves the opportunity for life," Tregle said during the sentencing phase.

Calarco said Miller's shooting of an unarmed Afghan civilian and leaving his body in a latrine, was not in accordance with military standards.

"Your sentence certainly makes a statement about how soldiers should behave," Calarco told the panel before sentencing.

Gittins said after the sentencing that he plans to appeal and ask for clemency.

"My concern is a verdict like this could cause soldiers to hesitate in the future," Gittins said.

Fort Campbell's commanding general must approve the sentence.