The state’s highest court ordered a new trial Friday for a Dorchester man convicted in the 1993 murder of a controversial Boston police detective, saying that newly discovered evidence about the detective’s relationship with corrupt investigators casts “real doubt on the justice’’ of the conviction.
The Supreme Judicial Court decision upheld a 2015 lower court ruling that freed Sean K. Ellis after 22 years, seven months, and 29 days in prison for the killing of Boston police Detective John J. Mulligan.
Suffolk District Attorney Daniel F. Conley promptly announced that he plans to again prosecute Ellis, meaning that Ellis may be tried for the fourth time in connection with the murder.
The SJC said its decision was based on new evidence that Mulligan was a corrupt police officer who robbed drug dealers and pimps, that the FBI had heard about a contract out for his murder, and that he associated with other corrupt detectives who later investigated his case. The high court said a jury should have been aware of such evidence.
Ellis maintains his innocence, saying he was the victim of the department’s push to quickly solve a high-profile murder. He and his lawyers called for an independent investigation into the corrupt police officers, their supervisors, and any other cases that may have been wrongfully prosecuted around the time Ellis was first charged in 1993.
“I would ask that they take another look, not only at my situation, but at the department as a whole, to make sure justice is being done in every case in Massachusetts,” Ellis, 42, said during a Friday morning meeting with reporters and his lawyers, Rosemary Scapicchio and Jillise McDonough.
Ellis, who was 19 at the time of his arrest, said he was “ecstatic” with the ruling and described what it felt like to work again, spend time with his family, and enjoy the outdoors in the 15 months since he has been free.
“I am happy to be home enjoying my family and freedom,” he said.
Juries in his first two trials were hung on murder convictions, though Ellis was convicted in each trial of possessing Mulligan’s gun and the one used to kill him. Ellis was convicted of murder in 1995. Conley inherited the case from his predecessors.
“Never once in more than 20 years has a single piece of reliable evidence undercut the compelling case against Mr. Ellis, and we intend to present that case to a jury once again,” Conley’s office said in a statement.
The unanimous Supreme Judicial Court decision, written by Chief Justice Ralph D. Gants, did not point to any evidence suggesting Ellis was innocent, but it cited several categories of newly discovered evidence that could provide a “powerful” defense.
The court cited evidence that Mulligan and several detectives who investigated his death had weeks earlier robbed a marijuana dealer of more than $26,000; informants had told the FBI that Mulligan was known for robbing pimps and drug dealers, that he “liked” young girls, and that a contract was out for his murder. Also, the court found, the police department had received several leads that detectives failed to investigate and that information was not turned over to the defense.
Prosecutors, however, argued that key pieces of evidence against Ellis remain: the murder weapon and Mulligan’s service pistol, with the fingerprint of Ellis’s then-girlfriend on it.
Boston Police Commissioner William Evans said before a peace walk in Roxbury late Friday afternoon that he was disappointed in the SJC ruling.
He said he had not spoken with Mulligan’s family, but recalled that he had worked with him.
“It’s always a tragedy when we have one of our officers killed and we get a verdict that goes against the department,” he said. “Our thoughts go out to the Mulligan family.”
A second man was also convicted of murder in the case, Terry L. Patterson, but he later had his conviction overturned on appeal. The SJC barred prosecutors from presenting questionable fingerprint evidence that was used to tie Patterson to Mulligan’s car, and prosecutors agreed in 2006 to settle on a reduced charge of manslaughter and a new sentence of 25 to 30 years in prison, with 22 years to serve. Patterson was released soon after, based on time served and accumulated good time.
Scapicchio said her client would not plead guilty to any agreement alleging murder, even if it avoids a new trial and spares him more time in prison.
“Sean didn’t do it, and he’s not pleading to it,” she said.
Mulligan was slain while working a paid detail at a Walgreens drugstore in Roslindale in the early morning of Sept. 26, 1993. In uniform and apparently sleeping in his Ford Explorer in front of the store, he was shot five times in the face with a .25-caliber pistol.
His 9mm Glock was stolen, what authorities called at the time a move by the culprits to claim the gun as a “trophy.”
Patterson and Ellis, who said he had gone to the store to buy diapers, were convicted in separate trials. Witnesses said they saw Patterson’s Volkswagen Rabbit at the scene; a witness, Rosa Sanchez, said she saw a man she later identified as Ellis crouched down by Mulligan’s car before the shooting; a forensic examiner initially reported finding Patterson’s fingerprints on Mulligan’s car; and Ellis’s then-girlfriend told authorities she saw Ellis retrieve two guns from his home and then leave them in her apartment. Later, she and a friend discarded the weapons — Mulligan’s pistol and the one used to kill him — in a field, where they were found by police.
The SJC had earlier rejected Ellis’s request for a new trial based on evidence that several of the investigators in the case were corrupt and they had tainted the investigation. One of them had known Sanchez from a past relationship with her aunt, and Scapicchio suggested that the officer influenced Sanchez’s identification as Ellis as the man at the scene.
Sanchez had initially identified another man as the one she saw, and so did her husband.
The SJC rejected that argument, but found that new evidence the lawyers discovered about Mulligan’s own corruption and his relationship with the investigators raises new and powerful questions.
Two of the detectives, Kenneth Acerra and Walter Robinson, pleaded guilty to federal corruption charges; the third, John K. Brazil, was immunized from prosecution in a corruption investigation by a federal judicial order in return for his testimony.
“These detectives would likely fear that a prolonged and comprehensive investigation of the victim’s murder would uncover leads that might reveal their own corruption,” Gants wrote in the 40-page decision Friday.
Gants also noted that other leads in the murder investigation, including tips that drug dealers wanted Mulligan dead, were not followed and that information was not turned over to the defense, possibly because authorities did not want to expose internal corruption.
“With this newly discovered evidence, a reasonable jury likely would have had diminished confidence in the integrity and thoroughness of the police investigation in general,” Gants said.Travis Andersen of the Globe staff contributed to this report. Milton J. Valencia can be reached at email@example.com. Follow him on Twitter @miltonvalencia.