Premeditation key in trial of U.S. soldier who killed fellow servicemen TACOMA, Washington (Reuters) - A U.S. soldier who pleaded guilty in the shooting deaths of five fellow servicemen at a military counseling center in Iraq faced a court-martial on Monday in which a judge's sentence will hinge greatly upon whether he finds premeditation. Army Sergeant John Russell pleaded guilty last month to killing two medical staff officers and three soldiers at Camp Liberty, adjacent to the Baghdad airport, in a 2009 shooting the military has said could have been triggered by combat stress. Russell, who was attached to the 54th Engineer Battalion based in Bamberg, Germany, struck a plea deal to avoid the death penalty in a case that marked one of the worst episodes of soldier-on-soldier violence in the Iraq war. The court-martial before a military judge at Joint Base Lewis-McChord in Washington state will determine whether he acted on impulse, as his defense attorneys argue, or with malice of forethought, as alleged by military prosecutors. Russell faces up to life in confinement without the possibility of parole, forfeiture of pay and a dishonorable discharge. At issue is whether the soldier "had the ability to premeditate his intention to kill," the judge, Colonel David Conn, said Monday. Russell's state of mind has been the focus of legal proceedings over the past year at Lewis-McChord. Defense lawyers said Russell suffered a host of mental ailments after several combat tours and was suicidal before the attack. An independent forensic psychiatrist, Dr. Robert Sadoff, concluded that Russell suffered from post-traumatic stress disorder and psychosis at the time of the shootings. Sadoff suggested Russell was provoked to violence by maltreatment at the hands of mental health personnel at Camp Liberty. Conn ruled on Monday that Sadoff, who relied on another doctor's findings that "brain abnormalities" affected Russell's judgment, would not testify. Defense attorneys will argue that damage to Russell's frontal lobe inhibited his judgment. "My plan was to kill myself," Russell said during his plea hearing. I wanted the pain to stop. Prosecutors said Russell, upset with a healthcare worker, stole a Ford SUV, locked and loaded one 30-round magazine into a M16-A2 rifle, and drove 40 minutes to the stress clinic area. There, he smoked a cigarette, removed identification tags and the gun's optic, and slipped into the clinic through the back entrance to commit the "five cold-blooded murders." "He knew everyone in that clinic was unarmed, helpless, and defenseless," an Army prosecutor said during pre-trial hearings, according to court documents obtained by Reuters. Editing by Cynthia Johnston and Doina Chiacu