SAN ANTONIO (AP) — Instructors and trainees at a Texas military base at the center of an Air Force sex scandal are under constant surveillance, a witness testified Thursday in the trial of an instructor facing rape and sexual assault charges.

Technical Sgt. Richard Capestro was the sole defense witness in the case of Staff Sgt. Luis Walker, who is accused of having illicit relationships with 10 women in basic training at Lackland Air Force base in San Antonio. He faces seven charges including rape, aggravated sexual assault, obstructing justice and violating rules of professional conduct. The case against him contains 28 total specifications of wrongdoing, and Walker faces up to life in prison.