In the pre-dawn hours of September 26, 1993, a chilling discovery was made in the parking lot of a Walgreens drugstore in Boston's Roslindale neighborhood. John James Mulligan, a 52-year-old White male and a 27-year veteran detective of the Boston Police Department, was found slumped in his Ford Explorer. He was working a paid security detail, a routine task in a long career, but his death was anything but ordinary.
Mulligan had been shot five times in the face in what was described as an execution-style killing. The methodical nature of the slaying, with no signs of a struggle and no broken windows, suggested a deliberate and personal act. His service weapon was missing from its holster.
The initial investigation cast a wide net, delving into the complexities of Mulligan's own controversial career. The detective was known for a tough policing style that had earned him numerous civilian complaints and a reputation as a "problem officer" within his own department. Investigators initially pursued the theory that his death was an act of revenge, a violent repercussion from one of the many enemies he had made on the streets of Boston. However, this line of inquiry soon shifted dramatically. The focus turned away from seasoned criminals with a vendetta and onto two local teenagers, 19-year-old Sean Ellis and 18-year-old Terry Patterson. The official theory became that the two youths had stumbled upon the sleeping detective and killed him simply to steal his gun as a trophy, a narrative that many found difficult to reconcile with the brutal, assassination-like nature of the crime.
Despite the public's skepticism, both Sean Ellis and Terry Patterson were arrested and, in 1995, convicted of first-degree murder in separate trials. The case, however, was far from closed and would unravel over the next two decades. Allegations of police corruption and investigative misconduct began to surface, casting a long shadow over the convictions. Key detectives involved in the case were later found to be corrupt, raising serious questions about the evidence and witness testimony they had procured. In 2000, Terry Patterson's murder conviction was overturned; he later pleaded guilty to the lesser charge of manslaughter and was released from prison in 2007 after admitting his involvement.
The fight for Sean Ellis's freedom was longer and more arduous. After multiple mistrials, his 1995 conviction was finally overturned in 2015 by a judge who concluded that "justice may not have been done," citing the involvement of the corrupt detectives in the original investigation. After serving 22 years behind bars, Ellis was released on bail. Finally, in 2018, the Suffolk County District Attorney's office announced it would not retry him for the murder, officially dropping the charges. The strength of the decades-old evidence had withered, and the proven corruption of the investigating officers had irrevocably compromised the case. While Ellis's convictions for possessing the murder weapon and Mulligan's stolen gun remained, the final chapter on who was truly responsible for the detective's execution-style death remained unsettled.
