Phoenix's police union has a secret deal with the department to purge dirty cops' disciplinary records

For two decades, the Phoenix police union has had a secret deal with the police department that required that the disciplinary records of cops would be "purged," so that no one, not even their supervisors, would be able to retrieve them.

As a result, Phoenix cops who repeatedly committed violent, corrupt acts -- including acts that resulted in severe injuries -- were allowed to serve on the force, even collecting commendations for their "good behavior."

The Arizona Republic undertook a deep investigation into the practice and uncovered more than 600 acts of wrongdoing committed by 525 cops (out of 3,000 PD employees) in just the past five years, with 90% of all "serious misconduct" incidents being purges from cops' records.

And as bad as this policy is, the Republic revealed that it was routinely abused, allowing cops to purge their records more quickly, and for graver offenses, than were officially permitted.

Scholarly work has found that serving alongside corrupt officers makes otherwise honorable officers corrupt, too, with a few bad apples actually spoiling the barrel. Allowing violent, corrupt cops to continue to serve, and to reoffend, compromises the whole force.

Officer Kevin McGowan, for example, earned top marks in his 2015 evaluation despite being disciplined for serious misconduct during the previous year.

An internal investigation concluded McGowan used excessive force when he stomped on an 18-year-old mans neck, driving his face into the tile floor of a convenience store and knocking out three of the man's teeth.

The incident was captured in surveillance footage taken from the store.