DA: Dorchester Man Who Served 22 Years For Murder Of Boston Detective Will Remain Free

The Suffolk County district attorney's office announced Monday that it will not retry a Dorchester man convicted in the murder of a Boston police officer 25 years ago, saying there is not enough evidence to win in a new trial.

Sean Ellis, 44, spent nearly 22 years in prison after being found guilty of first-degree murder in the slaying of Detective John Mulligan during an armed robbery in 1993. In 2015, a judge found he did not receive a fair trial and granted Ellis' motion for a fourth trial in the killing.

Ellis, who has maintained his innocence, has been free on bail since 2015. In 2016, the state's highest court upheld the judge's decision to grant him a new trial.

Boston officers involved in the murder investigation later pleaded guilty to unrelated corruption charges.

Suffolk County District Attorney John Pappas told reporters Monday that "the state of the evidence today makes it very unlikely" that prosecutors would secure a new conviction against Ellis. He blamed unreliable witnesses and the corruption charges against detectives in the original case.

"As we all know, Detectives Kenneth Acerra, Walter Robinson, and John Brazil disgraced themselves and tarnished their badges in a wide variety of criminal conduct unrelated to this case — the extent of which was unknown to prosecutors or defense counsel in 1995," Pappas said. “Perhaps more than any other factor, their shameful conduct presents a major challenge to our ability to put a successful case to a new jury."

Pappas added, however, that no evidence has ever pointed to another suspect beyond Ellis and Terry Patterson, a man who was tried and convicted separately in the case as Ellis' accomplice. He said Ellis' "convictions for possessing the murder weapon and Det. Mulligan’s service weapon, which was stolen from his body, remain undisturbed."

At the DA's announcement, Boston Police Commissioner William Gross said he did not believe Ellis was innocent.

"This new case would be based on the strength of the evidence, [on] what does the evidence look like after 25 years," he said. "And the decision was based upon that, not innocence — at all."

In Ellis' last trial, his attorneys argued that Patterson acted alone in the murder. Patterson served 12 years in prison before his release in 2006.

On Tuesday, Ellis' defense attorney Rosemary Scapicchio rejected the district attorney and police department's comments as a judge approved a motion to remove Ellis' GPS ankle monitor and drop the robbery charge in the case.

"If they thought for one second that Sean was responsible, they would’ve gone forward with the trial," Scapicchio said. "They know they can’t prove it because he didn’t do it. They steered it in the direction of Sean Ellis 25 years ago, and now they can’t fix it. They can’t find anyone out there who’s willing to say Sean did it."

She also says Suffolk County District Attorney-elect Rachael Rollins, who takes office on Jan. 2, likely would not have praised the current district attorney's handling of the case.