Meek Mill was released from prison on Tuesday after the Pennsylvania Supreme Court overrode his trial judge’s stubborn resolution to keep the hip-hop star behind bars. Judge Genece Brinkley had previously sentenced Mill to two to four years for alleged probation violations, with Mill’s defenders accusing the judge of punishing him out of a personal vendetta.

Soon after the decision, Mill tweeted his gratitude toward the current Philadelphia district attorney’s office, which backed Mill’s appeal, while also pledging this: “I understand that many people of color across the country don’t have [the] luxury [I did] and I plan to use my platform to shine a light on those issues.”

He also noted that this is not the end of his legal saga. Mill, whose legal name is Robert Williams, will remain on probation unless his underlying case is overturned. A key piece of evidence recently made public lends a good amount of weight to Mill’s case to clear his name: His arresting officer, and a key witness in his case, Reginald Graham, was found to be corrupt by an internal police investigation before he ever cuffed a 19-year-old Mill on a Philadelphia corner. Last week, three other Graham cases were tossed out by Judge Sheila Woods-Skipper because of issues with the officer’s “credibility.”

Indeed, Mill’s understanding that other “people of color across country” have faced the same sort of corruption that landed him in prison hits a lot closer to home than even his statement indicated.

Two of the men accused by Graham, siblings then in their 40s, were convicted of drug and gun charges from 2005 that hinged on a search of their home by the officer. The other was convicted for allegedly peddling cocaine. One of these men was sentenced to two and a half years in prison, another to a year on probation, and all three racked up hundreds of dollars in court fines and fees. (None of the defendants could be reached for comment.)

These three are among 105 people that defense lawyers are arguing were wrongfully convicted because of Graham’s involvement. Philadelphia District Attorney Larry Krasner, known for suing cops in his civil rights days, has attorneys reviewing all of these cases. The next hearing for a local judge to hear petitions to overturn these old convictions is scheduled for late June.

The scope of the convictions secured by these corrupt officers is jarring.

Mill’s case isn’t in this cohort for purely administrative reasons: His lawyers filed a petition for a retrial before the mass investigation proved Graham’s wrongdoing, so it stayed under Brinkley’s purview. That the other three cases were tossed is significant to Mill, however, because they predate his. So a local judge and Philly’s prosecutor have each agreed that Graham should have been sidelined years before he arrested Mill. This broader review was catalyzed by the March release of a “do not call” list—a dossier of “bad cops” compiled by the previous district attorney—but the initial review had previously cited a 2013 incident. Since the list was released, the DA’s office has obtained and reviewed files from a 2005 internal police investigation that allegedly found Graham to have stolen drugs on the job and lied about it, says Ben Waxman, Krasner’s spokesperson. Evidence revealed last week could push the date of proven corruption even further back to 2002.

Graham was one of 29 flagged officers on the “do not call” list, and so these overturned convictions represent the beginning of a wide-spanning case purge in Philadelphia. Brad Bridge, the public defender in charge of the review, said that he has marked about 5,000 potentially tainted files. He is negotiating with the judge to be allowed more than the 60 days that would normally be allotted by Pennsylvania law to present these cases to the court and expects an extension—but “there is a clock running,” he says.

The scope of the convictions secured by these allegedly corrupt officers is jarring, and it raises a larger issue: Why were these officers on the street and in the courtroom in the first place? Their higher-ups knew about the misconduct, and if the DA’s office did not, it could have found out.

Maintaining a “do not call” list is one way to increase transparency in criminal cases—so long as it’s not kept internal. This is a practice that is uncommon, but not unprecedented. But this doesn’t mean that prosecutors are in the dark about corruption even in places where these lists don’t exist. “It’s an open secret in most urban court systems prosecutors know that there are certain officers that will stretch the truth if not give an outright lie,” says David Harris, a professor at the University of Pittsburgh School of Law who studies police behavior.

The argument against maintaining such a list is that minor indiscretions or debatable accusations, if officially documented and disclosed, could have very negative consequences on an officer’s career. In Baltimore, for example, the state’s attorney used to keep such a list but stopped because it became controversial for this reason. A subsequent state’s attorney candidate promised to abolish the city’s list, which he promptly did after taking office in 2011.

Harris is doubtful that wrongly accused officers have actually been marked in Philadelphia, though. “If an officer’s name is on that list and it doesn’t belong there it would be terrible,” he told me. “But prosecutors and police work hand in hand every day—if they have a reputation of not being trustworthy it’s bigger than one incident.”

Harris continued, “The bigger question is: If prosecutors don’t trust them to give testimony, why are those officers still in that business?”

In the case of Meek Mill, it’s one that should have been asked a long time ago.