LOS ANGELES -- During two tours of duty in Iraq, Navy corpsman Melson J. Bacos said he experienced everything combat had to offer -- fire fights with insurgents, soldiers dying in his arms, thoughts of whether he'd live another day. Now he's got another unnerving assignment. On Friday, the 21 year old is scheduled to give testimony that military prosecutors hope will help them convict seven Marines accused of kidnapping and murdering an Iraqi man in the town of Hamdania. Bacos, a medic who patrolled with the Marines, will have similar charges dropped in exchange for testimony during his court...