LOS ANGELES — Prosecutors say a Los Angeles police officer has been charged with sexually assaulting a 15-year-old cadet.

The Los Angeles County district attorney’s office says Robert Cain is expected to be arraigned Friday on charges that include unlawful sexual intercourse.

Cain was arrested in June amid a widening probe into wrongdoing in the department’s cadet program for minors who are aspiring officers.

Prosecutors say Cain befriended the teenage cadet and had sex with her on three occasions at three locations.

Cain’s attorney declined to comment Friday on the allegations.

In a separate case, Cain has pleaded not guilty to 10 felonies after police said they found illegally modified assault rifles and other restricted firearms while searching his San Bernardino County home during the sex investigation.