‘They got a private police force for themselves and their friends,” U.S. Attorney Preet Bharara said as he laid out corruption charges against some NYPD brass.

As Bharara described the quid pro quo relationship between top NYPD supervisors and real estate developers in an alleged pay-for-favors scandal, Commissioner Bill Bratton stood next to him. The Justice Department had charged three police bigwigs with the help of the NYPD’s Internal Affairs Bureau. “The system works,” Bratton claimed.

No, the system doesn’t work.

Deputy Insp. James Grant, who, according to court papers, complained to businessmen about “elves” who “didn’t come for [expletive] Christmas,” retired last month rather than face an IAB interview. Grant and three other police supervisors who have filed for retirement will keep their pensions because Bratton did not fire them. Mayor Bill de Blasio, who received donations from the same developers, has defended their right to retire.

Bratton says he knew of the federal investigation when he was appointed in 2013. Grant and other officers charged by Bharara’s office were promoted during that time. Grant, who moved from Brooklyn’s 72nd Precinct to the more desirable 19th Precinct on the Upper East Side, had a developer friend call an NYPD chief to secure the move, the federal complaint indicates. Grant was transferred in June 2014 in a decision approved by Bratton, who can block Grant’s retirement.

It was only after a leak to the media about the investigation that the cops were held to account. Faith in the investigation, then, may be based on how strongly you believe in the system. Can you trust an NYPD-involved investigation of the NYPD? The independence and depth of a federal probe that the department knows about should be scrutinized.

Twenty-one years ago, a younger Bratton dismissed then-head of internal affairs Walter Mack because he wanted more resources and independence.

Bratton has pledged to root out bad apples. To city and state officials who’ve been deafeningly silent: form an independent commission that checks out the entire apple tree.

Josmar Trujillo is a trainer, writer and activist with the Coalition to End Broken Windows.