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District Attorney Launches New Probe Into Fired Antioch Detective

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Former Antioch police Sgt. Santiago Castillo was suspected 'as far back as 2010' of giving 'confidential police department information to known criminals,' according to recently released internal investigation records.

The Contra Costa County District Attorney is investigating a former Antioch detective fired in 2017 for leaking sensitive information to drug dealers for as long as seven years, and the county public defender wants a review of any case he worked on that resulted in people being charged with crimes.

The Antioch Police Department fired Sgt. Santiago Castillo in 2017 for the alleged leaks as well as submitting time sheets for hours he didn’t work and stealing evidence, according to records released under the state’s new police transparency law.

Antioch Police Chief Tammany Brooks met with the staff of then-District Attorney Mark Peterson to discuss criminal options, but no charges were filed. The FBI also investigated Castillo but no federal charges were filed.


District Attorney Diana Becton, elected last year, is now investigating “everything that’s been raised” in records released about Castillo, her spokesman Scott Alonso said Thursday. Antioch never made a formal submission of charges against Castillo, but the DA’s office was involved in the case.

The internal records released by the Police Department late Monday revealed that an inspector in the DA’s office participated alongside an Antioch investigator in at least one interview of an unnamed informant about Castillo’s involvement with criminals.

“It was a request for investigative assistance,” Alonso said, adding that it was the DA’s office only involvement at the time. The information from that one interview was not enough to launch an independent investigation in the district attorney’s office, Alonso said. Brooks later met with Peterson’s staff, but no charges were filed.

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Contra Costa Public Defender Robin Lipetzky is calling for a review of all prosecutions “that might have been impacted by” Castillo, she wrote in an emailed response. It was not immediately clear Thursday how many cases that might be, but it’s likely to be “a fair amount,” Alonso said, noting that Castillo was a prominent detective.

Castillo could not be reached for comment. His attorney did not respond to an email.

This is the second time that recent reporting on the release of police disciplinary records in Contra Costa County has led to Lipetzky asking for a review of cases involving problem officers. She made a similar request last month for cases involving Walnut Creek Officer Curtis Borman, who falsified 31 police reports and lied when asked about missing drugs found during a traffic stop.

The new law, Senate Bill 1421, requires police departments to release internal records of officer-involved shootings and other uses of force, police dishonesty and sexual assault. The Antioch records released Monday show internal affairs investigators believed Castillo had improper relationships with criminals and shared secret police information. The leaks could have put other officers’ lives at risk, according to the internal reports.

Castillo was suspected “as far back as 2010” of giving “confidential police department information to known criminals,” Antioch police Captain Tony Morefield wrote in a 60-page report.

Castillo leaked information to “a known drug user and associated with many key figures involved in criminal street gangs, drug sales and even homicides in Antioch,” Morefield wrote.

In 2014, police became more suspicious when informants being used in a major drug investigation indicated that an Antioch sergeant was communicating with a drug dealer, whose name is blacked out in the documents.

Phone records showed 42 exchanges between Castillo’s personal cell phone and the drug dealer’s phone, Morefield wrote, and seven connections with the detective’s work cell. But the department didn’t act at that time.

Police later learned that Castillo had ties to another unnamed drug dealer who had attended a barbecue at the detective’s home. The detective claimed that person wasn’t a gang member or drug dealer “despite the fact that (the person) was covered in gang tattoos, including a gang moniker,” according to a report.

Even as the DA begins investigating Castillo anew, he is being prosecuted in a separate matter.

After being fired from the Antioch Police Department, Castillo got a job as a loss prevention investigator at a Target store in Pittsburg, court records show. He was arrested last year on misdemeanor charges of stealing items from the store.

Sukey Lewis of KQED News contributed to this report.

This story was produced as part of the California Reporting Project, a collaboration of more than 30 newsrooms across the state to obtain and report on police misconduct and serious use-of-force records unsealed in 2019.

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