PHOENIX — Phoenix Police Chief Jeri Williams was slapped with a one-day suspension after lawyers hired by the city issued a report that heavily criticized her agency’s role in a now-discredited gang case filed against demonstrators arrested nearly 10 months ago at a police protest.

The report released Thursday said the decision to charge 15 protesters with assisting a street gang was made without seeking input from Phoenix police’s gang enforcement unit. It also said the agency didn’t have credible evidence to support the claim that the protesters were members of an anti-police gang called “ACAB,” meaning “All Cops Are Bastards.”

Concluding that ACAB is a slogan rather than a group, the outside lawyers said they “found no credible evidence to support the assertion that ACAB is a criminal street gang, that it organized the protest of October 17, or was prone to violence.”

The gang charges were later dismissed at the request of prosecutors.

The city is asking the Arizona Attorney General’s Office to investigate any criminal matters arising from the report. Three assistant chiefs were removed from those roles, and a sergeant at the center of the report was put on administrative leave.

The report came a week after the U.S. Department of Justice announced a widespread investigation of the Phoenix Police Department to examine whether officers have been using excessive force and abusing people experiencing homelessness.

The probe also will examine whether police have engaged in discriminatory policing practices and will work to determine if officers have retaliated against people engaged in protected First Amendment activities.