John L. Mone, Associated Press
In this June 22, 2012, image made from video, female airmen march during graduation at Lackland Air Force Base in San Antonio. A widening sex scandal has rocked Lackland Air Force Base in Texas, one of the nation's busiest military training centers, where four male instructors are charged with having sex with, and in one case raping, female trainees.

SAN ANTONIO — An instructor at an Air Force base in San Antonio is facing rape and sexual assault charges at court-martial, the first to stand trial in a sex scandal implicating a dozen people that has rocked one of the busiest military training centers.

Staff Sgt. Luis Walker faces up to life in prison and a dishonorable discharge if convicted.

Walker is among 12 instructors at Lackland Air Force Base who are being investigated in the scandal. Walker faces the most serious charges. He is charged with 28 counts, including rape, aggravated sexual contact and multiple counts of aggravated sexual assault.

Procedural issues were discussed Monday morning and opening statements are expected Monday afternoon.

Walker's father and two other family members were in the courtroom at the base.