OAKLAND — The top brass at the Oakland Police Department was aware for months of allegations that several officers had had sex with a minor, yet they downplayed the wide-ranging scandal, conducted a halfhearted, inept investigation, and only pursued a criminal probe and disciplinary actions after the U.S. District Court intervened, according to a scathing report released Wednesday.

“OPD’s investigation of this case … was seriously deficient,” investigators Edward Swanson and Audrey Barron wrote in a report commissioned by U.S. District Court Judge Thelton Henderson, who has been overseeing court-ordered reforms of OPD under a longstanding negotiated settlement agreement. “If not for the court’s intervention, we have no confidence that correct discipline would have ever been imposed, criminal charges filed, or departmental shortcomings examined.”

Henderson brought in the two attorneys to conduct a probe after Oakland Mayor Libby Schaaf’s outside investigator failed to interview any witnesses or issue any findings in the department’s handling of the internal probe of a widespread sex scandal that involved several Oakland police officers and the teenage daughter of a police dispatcher, according to the report.

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Oakland police sex scandal: triggered ‘crisis’ in department, monitor says

Oakland police sex scandal: City hires private investigator to find media leaks The young woman, who used to go by the name Celeste Guap, has said she had sex with as many as 30 police officers from Bay Area departments, some while she was a minor and others in exchange for giving her confidential police information or protection. Five Oakland officers or former officers have been charged in the case.

The attorneys reserved much of their criticism for former police Chief Sean Whent, who they said, “sent an unmistakable signal that this case was not a priority.” The report alleges that Whent pressured internal affairs to end its investigation.

He abruptly resigned last June as details of the extent of the scandal and the involvement of OPD officers grew, and there was a revolving door of interim chiefs until Anne Kirkpatrick’s hiring in January. At the time, Schaaf decried a frat house atmosphere in the department.

The investigators were also critical of Schaaf and City Administrator Sabrina Landreth for their handling of the case.

“Despite the fact that the investigation stalled, the city administrator and the mayor did not press (their hired outside) investigator to find out whether OPD’s investigation was conducted appropriately, nor did they inquire as to the status of the investigation,” the report said.

At a news conference at City Hall on Wednesday, Landreth said city officials treaded carefully “so as to not compromise our ability to hold these officers accountable.”

Schaaf acknowledged that the investigation probably would not have been handled properly were it not for the monitor, but she said her administration took serious action.

“We disciplined 12 officers seriously and quickly; four termination findings,” Schaaf said. “Four officers are being held on criminal charges.”

The allegations, which made national headlines, first came to light in September 2015 when Oakland police Officer Brendan O’Brien killed himself. He left behind a suicide note revealing the scandal and implicating other officers. The department opened a criminal investigation but, according to the report, closed it after just one week.

According to the court’s investigative report, Guap deleted cellphone messages from at least six people, who she said worked at OPD, in the presence of investigators who were interviewing her. It also said that one department investigator referred to the teen as a “whore” during an interview with one of the officers alleged to have had sex with her.

The court-appointed monitor found out about the allegations against the officers in early 2016 and pressed OPD to assign new staff to investigate. The Alameda County district attorney also began investigating the allegations.

Last month, the city agreed to pay the now 19-year-old woman $989,000 to settle her civil claim against the city. Also last month, she testified against former Oakland officer Brian Bunton, who was ordered to stand trial for felony obstruction of justice and a misdemeanor for engaging in prostitution.

John Burris, one of the attorneys representing the young woman, said he was most surprised by the “covert activity” of police supervisors who did not pursue leads in an apparent effort to prevent more officers from being implicated.

“If the chief had told the monitors on the very night O’Brien committed suicide that there was a suicide note and phone messages linking the officers to being involved with this woman in a sexual way, the monitors would have been involved in actively pursuing all of the leads,” Burris said. “This case should have never reached the level it did.”

Chief Kirkpatrick said she does not view the report as a setback.

“I see reports like this … as a launching pad for the future,” she said. “We are ready to go forward.”