The US soldier accused of slaughtering 16 Afghan villagers last weekend saw his friend's leg blown off the day before the rampage, his lawyer said.
Attorney John Henry Browne said his client's family provided him with details of the injury to another US soldier. The details have not been independently verified.
"His leg was blown off, and my client was standing next to him," he said.
Mr Browne said the incident affected all of the soldiers at the base. It isn't clear whether it might have helped prompt the middle-of-the-night attack on civilians in two villages last Sunday.
The suspect had been injured twice during his three previous deployments to Iraq, Mr Browne said. He said the soldier has two young children, aged three and four.
The soldier, a 38-year-old father of two, who is originally from the Midwest, was deployed last December with the 3rd Stryker Brigade and on February 1 was attached to a "village stability operation",
Mr Browne described him as highly decorated. During tours in Iraq, the soldier suffered a concussive head injury in a car accident caused by a roadside bomb and suffered a battle-related injury that resulted in surgery to remove part of his foot.
He was screened by health officials after the head injury before he redeployed, Mr Browne said. He did not know if his client had been suffering from post-traumatic stress disorder, but said it could be an issue at the trial.