Sean Ellis Granted New Trial For Remaining Gun Conviction In Boston Police Officer's 1993 Murder

BOSTON (CBS) -- Sean Ellis, the man at the center of the Netflix documentary Trial Four, earned a significant legal victory Tuesday. A judge is allowing Ellis's motion for a new trial on the gun conviction that remains on his record from the 1993 killing of Boston Police Detective John Mulligan.

Ellis was initially convicted of murdering Mulligan and served 21 years in prison for it before the conviction was overturned in 2015.

"This whole case is a very sad chapter in the history of the criminal justice system. Thankfully, this chapter seems to be nearing its conclusion," said Superior Court Associate Justice Robert Ullman in his decision.

Suffolk County District Attorney Rachael Rollins has said in the past if Ellis is granted a new trial for the gun conviction, she will not re-prosecute him, meaning Ellis's record will be wiped clean.

In a statement on Tuesday, Rollins said both the Mulligan and Ellis families have suffered since Mulligan's death.

"As Judge Robert Ullman found today, 'Justice was not done' in this case. We need to continue to work together as law enforcement partners to make sure the criminal and unconstitutional behavior that infected every part of the investigation into Detective Mulligan's death, can never happen again. I am committed to doing just that. Filing a nolle prosequi is part of that commitment," said Rollins.