Roberto Machuca, 32, of Riverside turned himself in Monday and was charged with five felony sex crimes for allegedly having sexual encounters with a 16-year-old girl enrolled in the Garden Grove Police Department's Explorer program.

The Orange County District Attorney's office filed charges on July 28. He pleaded not guilty. A judge set bail at $100,000 and ordered Machuca to surrender all his firearms and his passport.

His next court date is a pretrial hearing on August 4 at the Stephen K. Tamura West Justice Center in Westminster.

The charges

Machuca faces three felony counts of unlawful sexual intercourse with a minor more than three years younger than himself, one count of sexual penetration by a foreign object of a minor, and one count of oral copulation with a minor. If convicted on all five, he faces up to five years in state prison and a 10-year sex offender registration requirement.

How it started

Machuca joined the Garden Grove Police Department in 2019 and served as an advisor to its Explorer program. The program accepts volunteers ages 14 to 21 who want to learn about law enforcement careers, and the advisor role put Machuca in regular contact with the participants.

On June 26, the department received a report about an inappropriate relationship between Machuca and a 16-year-old participant. He was placed on leave immediately. When he showed up to his shift the following day, he was arrested. He is no longer employed by GGPD.

Prosecutors say the sexual encounters began in May 2026 — about a month before the department first learned of the relationship.

DA's statement

"Law enforcement officers occupy a position of immense trust, and he exploited that trust to take advantage of a child for his own sexual gratification," said Orange County District Attorney Todd Spitzer. "That conduct will never be tolerated among the ranks of those sworn to protect and serve, and justice will be pursued to the fullest extent."

Senior Deputy District Attorney Sarah Rahman of the Sexual Assault Unit is handling the prosecution.

Earlier this year, Westminster Police arrested a 19-year-old on five felony charges after he allegedly sexually assaulted an 8-year-old child in a residential neighborhood. That case remains pending.

Machuca has pleaded not guilty to all charges.