TACOMA: A US soldier accused of killing five fellow servicemen at a military combat stress centre in Baghdad in 2009 was psychotic and suffered from post-traumatic stress disorder during the shooting frenzy, a top US forensic psychiatrist testified on Tuesday.

Sergeant John Russell, 48, is accused of going on a shooting spree at Camp Liberty, near the Baghdad airport, in an assault the military said at the time could have been triggered by combat stress.

Russell, of the 54th Engineer Battalion based in Bamberg, Germany, faces five charges of premeditated murder, one charge of aggravated assault and one charge of attempted murder in connection with the May 2009 shootings.

Six months ago, he was ordered to stand trial in a military court that has the power to sentence him to death, if he is convicted.

Russell’s civilian attorney, James Culp, entered no plea at an arraignment on Monday at a military base in Washington state.

Russell’s court martial is tentatively set for mid-March and could last four to five weeks, attorneys said on Tuesday.

If the defence can persuade a jury that Russell was not in control of his actions, it may be able to argue that he is not legally responsible and could spare him from the death penalty, if convicted.

In a second day of hearings to discuss Russell’s state of mind at the time of the shooting and establish what evidence or testimony to admit at the court martial, Robert Sadoff, a University of Pennsylvania forensic psychiatry expert, gave the opinion that Russell was suffering from post-traumatic stress disorder.

Russell has “dissociative disorder,” or a lack of memory about the shootings, said Sadoff, who examined Russell for a total of 20 hours after the shootings.