Doctors to take stand for U.S. soldier's defense in Afghan massacre case TACOMA, Washington (Reuters) - Attorneys for the U.S. soldier who massacred 16 unarmed Afghan civilians last year will call witnesses on Thursday as they try to show he suffered a breakdown under the pressure of his final deployment to Afghanistan. The first witnesses to be called by the defense in the sentencing phase of Army Staff Sergeant Robert Bales' trial will be a number of medical doctors flown in from across the United States, his attorney John Henry Browne told reporters. Defense testimony on Wednesday appeared aimed at telling the story of Bales' transformation from a dutiful young man to a soldier who his civilian attorney says broke under the pressure of overseas deployment. "I don't think anybody with a rational mind could say Bob Bales didn't snap," Browne told reporters on Wednesday after the court-martial session before a military jury. A decorated veteran of four combat tours in Iraq and Afghanistan, Bales pleaded guilty in June in a deal that will spare him the death penalty. The jury will decide if he will spend the rest of his life in prison or if he will be eligible for parole after 20 years. After Bales' brother testified on his behalf of Wednesday, Browne he planned to call up to 10 more witnesses, including Bales himself and the doctors. William Bales on Wednesday described his brother as a good-natured young man who felt duty-bound to enlist in the Army in the aftermath of al Qaeda attacks on the United States on September 11, 2001. The prosecution rested its case on Wednesday after calling to the stand a string of witnesses including nine Afghans, among them a man who lost six of his seven children. They testified to the devastating toll inflicted by Bales on civilians before dawn on March 11, 2012, during two forays from his military base in Kandahar province. Bales' attorneys have said he suffered from post-traumatic stress disorder and a brain injury even before his deployment to Afghanistan. Browne said on Wednesday that the defense's final witness would be Bales himself, who under military court rules would be exempt from cross-examination. The killings marked the worst case of civilian deaths blamed on a rogue U.S. soldier since the Vietnam War and further eroded strained U.S.-Afghan relations after more than a decade of conflict in that country. Editing by Alex Dobuzinskis, John Stonestreet