A U.S. Army officer was sentenced to 25 years in prison by a military jury in Kentucky Saturday for shooting and killing an Iraqi detainee during an interrogation in Iraq.

First Lt. Michael Behenna of Edmond, Okla., was convicted a day earlier of murder and assault, but acquitted of making a false statement. He had faced up to life in prison.

"We are disappointed at the jury's verdict and the sentence," Behenna's lawyer Jack Zimmermann said.

Zimmermann said he has filed a motion for a mistrial, claiming prosecutors withheld evidence that could help Behenna's defence. The judge has scheduled arguments on the motion Monday, Zimmermann said.

Behenna testified he was trying to defend himself when he shot Ali Mansour Mohammed, and that the detainee reached for the officer's gun in a secluded railroad culvert near Beiji, Iraq, in May.

Prosecutors said the detainee was defenceless against Behenna, and the officer's threats and other actions showed he had planned to kill the man.

Zimmermann argued Behenna wouldn't have brought along an Iraqi translator if he had planned to kill the detainee.

Behenna testified that he threatened Mohammed and pointed his gun at him to scare out information about a roadside bombing that had killed two members of his platoon.

After the detainee was shot twice, once in the head and once in the chest, another soldier testified that he tossed an incendiary grenade on the body.

Staff Sgt. Hal Warner pleaded guilty this month to charges of assault, maltreatment of a subordinate and making a false statement. He was sentenced to 17 months in prison and testified against Behenna.