Alexander Villa was one of three defendants charged in the murder of Clifton Lewis, and the only one who was still incarcerated before Wednesday.
The Cook County State's Attorney's Office dropped its case against Villa Wednesday, making him the third defendant whose case was dropped in the officer's 2011 murder.
Villa asked a judge to overturn his life sentence, based on allegations that prosecutors hid crucial evidence that would've proven his innocence.
The alleged misconduct prompted prosecutors to drop charges against Villa's co-defendants, Edgardo Colon and Tyrone Clay, last year, nearly 12 years after the men were arrested.
A large group of Villa's family and friends attended Wednesday's criminal court hearing at 26th Street and California Avenue in support. All were wearing matching shirts.
On the other side, a group of police officers with the Fraternal Order of Police also attended the hearing.
The 41-year-old slain Chicago police officer was working as a security guard at a West Side convenience store in 2011 when he was shot and killed trying to break up a robbery.
Lewis' sister said this feels unjust and unfair to their family. She asked: If these three men didn't kill her brother, who did?
The officer's family now wants his case to be picked back up so they can find out who killed Clifton Lewis.
It's unclear at this time if prosecutors will reopen the case.
Villa's lawyer said he likely won't be released until Thursday.
The video in the player above is from an earlier report.