Judge throws out remaining gun charge against Sean Ellis in 1993 killing of Boston police officer By John R. Ellement Globe Staff,Updated May 4, 2021, 4:24 p.m. Email to a Friend Sean K. EllisPat Greenhouse/Globe Staff Calling it a âsad chapter in the history of our criminal justice system,â a Suffolk Superior Court judge on Tuesday effectively ended the prosecution of Sean K. Ellis in the killing of a Boston police detective, John J. Mulligan, who was shot in the face with a .25-caliber pistol in Roslindale in 1993. Ellis spent 22 years in state prison before his murder conviction was overturned because of police and prosecutorial misconduct. Speaking at a hearing that lasted just five minutes, Judge Robert Ullmann said Ellisâs conviction for illegal firearm possession was likewise flawed and could not stand.