Air Force Base Instructor Guilty of Sex Assaults With 11 more instructors accused, case forces major review of Air Force By Mark Russell, Newser Staff Posted Jul 21, 2012 7:50 AM CDT 31 comments Comments Air Force Staff Sgt. Luis Walker arrives for the fourth day of his trial at Lackland Air Force Base in San Antonio, Texas, Friday. (AP Photo/San Antonio Express News, Billy Calzada) (Newser) – Staff Sgt. Luis Walker, an instructor at Lackland Air Force Base, was found guilty yesterday of raping one trainee and sexually assaulting several others, reports AP. Walker faces life in prison and a dishonorable discharge after being found guilty on 28 counts, including adultery, violating regulations, and committing sexual crimes against female trainees, notes the San Antonio Express-News. Thirty-one women have accused Walker and at least 11 other instructors of sexual misconduct over a two-and-a-half year period, which has led to a major policy review across the Air Force. "We're not satisfied that this one unit is all there is," the commander of the Second Air Force, which oversees basic training, tells the New York Times. "We want to assure ourselves through a disciplined approach that we’ve caught everything or everyone involved in this kind of behavior." The Defense Department estimates there may be up to 19,000 sexual assaults a year across the services, although just 3,192 were reported in 2011, with 191 convictions.