A new Netflix documentary series tells the story of a Boston man freed after 22 years in prison

The story of Sean Ellis will be told by Netflix in the eight-part series "Trial 4."


A new Netflix documentary series will examine the case of a Dorchester man who spent 22 years in prison after being found guilty of murdering a Boston police detective before being freed in 2015.

“Trial 4,” which debuts Nov. 11 on Netflix, tells the story of Sean Ellis, who was charged with armed robbery and first-degree murder in the 1993 death of Boston Police detective John Mulligan. Ellis was found guilty and sentenced to life in prison in 1995 during his third trial after the first two resulted in hung juries.

A second man, Terry L. Patterson, was also found guilty on murder charges, but later had them reduced to manslaughter on appeal and was released in 2006 on time served and good behavior, according to The Boston Globe.


Mulligan, 52, was shot five times in the face with a .25-caliber pistol on Sept. 26, 1993, while working a detail at the Walgreens on American Legion Highway. Mulligan was reportedly inside an SUV, sleeping, when the shooting occurred, and his service weapon, a 9mm Glock pistol, was stolen.

The show begins with Ellis, who has always maintained his innocence, out on bail awaiting his fourth trial on first-degree murder charges — hence the title “Trial 4.”

“My name is Sean Ellis and I was wrongfully convicted of murder at 19,” Ellis says in the trailer. “Now I’m facing my fourth trial and the possibility of going back to prison for life.”


Attorneys for Ellis had long asked for a new trial based on questions relating to the case evidence and the fact that the trio of lead detectives in Mulligan’s murder investigation were corrupt. Two of the detectives, Kenneth Acerra and Walter Robinson, pleaded guilty to federal corruption charges in 1998, while the third, John K. Brazil, was given immunity in exchange for his testimony in the case.

Additionally, Rosa Sanchez, a witness who placed Ellis at the crime scene, initially identified the wrong person in a photo lineup. She lived in the same house as Acerra, who was in a relationship with Sanchez’s aunt, according to the Globe.


In 2015, Ellis was released on bail after a judge ordered a new trial, saying that exculpatory evidence had been withheld from the defense.

That new evidence included the fact that one BPD officer had implicated another in the murder, and that Mulligan himself was corrupt, according to the Globe.

In 2018, prosecutors declined to pursue a fourth trial for Ellis, with acting District Attorney John Pappas saying that while the 1995 trial “proved Mr. Ellis’s guilt beyond a reasonable doubt,” prosecutors weren’t convinced a new trial would end with a guilty verdict.

“In the 25 years since Det. Mulligan was murdered in cold blood, not one piece of evidence developed by prosecutors, defense counsel, or anyone else has pointed to anyone but Sean Ellis and Terry Patterson,” Pappas said. “Of all the people in all the world who might have killed John Mulligan, only they were present at the time and place he was killed — by their own admissions, supported by eyewitnesses and physical evidence.”


In the first trailer for “Trial 4,” documentarians speak to multiple sources, some who believe Ellis is innocent and some who maintain he is guilty.

One interview subject is Boston Globe columnist Adrian Walker, who says in the trailer that he believes “the cops were just looking for someone to pin this murder on.”

“The death of a police officer, it’s not handled like other homicides,” Walker says in another clip. “And this one wasn’t.”

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