Former Oakland cop will not face charges in sex assault case

Oakland Mayor Libby Schaaf, left, and former Oakland Chief of Police Sean Whent announced on Friday, May 13, 2016, that an internal investigation was launched into alleged sexual misconduct by four Oakland police officers. less Oakland Mayor Libby Schaaf, left, and former Oakland Chief of Police Sean Whent announced on Friday, May 13, 2016, that an internal investigation was launched into alleged sexual misconduct by four Oakland ... more Photo: Ben Margot, Associated Press Photo: Ben Margot, Associated Press Image 1 of / 4 Caption Close Former Oakland cop will not face charges in sex assault case 1 / 4 Back to Gallery

A former Oakland police officer, one four under investigation for alleged sexual misconduct while a member of the department, will not face prosecution on a charge of forcible sodomy of a young woman in a Contra Costa County park, officials said Thursday.

A Contra Costa County prosecutor said there was “insufficient evidence” to charge Terryl Smith with a crime stemming from the Feb. 1 incident involving an 18-year-old woman in Wildcat Canyon Regional Park in Richmond.

The announcement by Paul Graves, who heads the sexual assault unit of the Contra Costa County District Attorney’s office, came just hours before a surprise announcement by Oakland Mayor Libby Schaaf that Police Chief Sean Whent submitted his resignation.

It was not immediately clear if the ongoing investigation of Smith and three other Oakland police officers on sexual misconduct allegations had anything to do with Whent’s resignation.

“The criminal investigation involving a former Oakland police officer is closed,” Officer Johnna Watson, a Police Department spokesman, said without elaborating or mentioning Smith by name.

She added that an administrative investigation into the sexual misconduct allegations lodged against Smith and three other officers will continue.

The four Oakland officers were placed on leave in May as part of the investigation that began following the 2015 suicide of Oakland police Officer Brendan O’Brien and the 2014 suicide of that officer’s wife, Irma Huerta Lopez.

During a May 13 press conference called by Whent and Schaaf, officials revealed that during the investigation of O’Brien’s death, evidence was recovered that lead them to launch an Internal Affairs investigation into allegations of potential sexual misconduct, possibly with an underaged girl. They declined to discuss the evidence.

Smith resigned on May 17 after being placed on leave, said Watson. Another officer being investigated also resigned shortly after being placed on leave.

Watson said she could not discuss whether Smith was still being investigated for additional sexual misconduct allegations.

The Alameda County district attorney’s office is also conducting a parallel investigation into the sexual misconduct case.

Jenna Lyons is a San Francisco Chronicle staff writer. Email: jlyons@sfchronicle.com Twitter: JennaJourno