How accurate is Hulu’s ‘Boston Strangler’? Here’s what to know.

Keira Knightley in "Boston Strangler."20th Century Studios

“Boston Strangler” premieres on Hulu on Friday, and is based on the true story of the notorious serial killer (or killers) who strangled 13 women around Boston between 1962 and 1964. Starring Keira Knightley as reporter Loretta McLaughlin and Carrie Coon as colleague Jean Cole, the film follows two investigative journalists as they report on the terrifying string of murders.

“Having lived through those times, I can confirm it was a very scary period,” one reader wrote in an email to the Globe on Thursday.

But there’s much about the crimes that remains shrouded in mystery. Sixty years later, all but one of the 13 cases remain open.

As audiences get reacquainted with this dark time in Boston’s past, questions around accuracy will likely arise. And while director Matt Ruskin aimed to achieve authenticity, this is Hollywood, where creative liberties are allowed.

So — just how true is this true-crime thriller? Here’s what to know.

Spoilers ahead.

The ritualistic stranglings

All 13 women were indeed murdered in the gruesome, ritualistic ways described in the film. Many of the victims were found dead days later, with nylon stockings or the belts of bathrobes tied around their necks in a bow. All of the victims were sexually assaulted, and their apartments were left ransacked, with no signs of break-ins or traces left behind.

Boston on alert

“Don’t open the door to strangers,” law enforcement can be heard warning Boston’s general public in the film. This also happened in real life.

“Few women set out on the street alone, day or night,” reporter Loretta McLaughlin wrote in the Boston Globe in 1992, looking back on the case. “Locks, door chains, guard dogs, and weapons were bought faster than they could be stocked.”

The victims

The victims depicted in the film are the true victims of the Boston Strangler crimes.

The victims ranged between the ages of 19 and 85. Most worked as nurses in a hospital and had an affinity for classical music. Many lived alone and were described as “matronly,” according to McLaughlin’s 1992 look-back.

Because of the varying ages of the victims, many started to believe there could be more than one killer.

‘Two Girl Reporters Analyze Strangler’

McLaughlin starts to put the pieces together after the fourth murder, and she persuades her editor to let her pursue the case.

“Why? They are nobodies,” her editor said of the four murdered victims.

“That’s the whole point. Why should anyone be going around killing women who are no one?” McLaughlin responds. A version of this conversation plays out in both the movie and in real life.

Soon after, colleague Jean Cole is also assigned to the story. “Two Girl Reporters Analyze Strangler” is a real headline published in the Boston Record American as McLaughlin and Cole began covering the homicides.

As is depicted in the film, McLaughlin and Cole’s photos are printed next to the article in the paper — an effort to sell more papers.

But McLaughlin and Cole held their ground, and their reporting led to changes in how the police handled the cases.

Massachusetts Attorney General Edward Brooke declared a special task force would be set up so that all five police departments working on the homicides could coordinate their findings. This task force was set up after Jean Cole suggested in an article that law enforcement create a centralized system.

McLaughlin and Cole also get credit for coining the phrase “Boston Strangler.”

Carrie Coon as Jean Cole.20th Century Studios

Trouble at home

McLaughlin and Cole balanced their careers with having a family in both the film and real life.

“She managed to not bring it home,” McLaughlin’s son Mark McLaughlin said in an interview on the “Truth And Lies: The Boston Strangler” podcast, reported by Dick Lehr.

As depicted in the film, McLaughlin’s once-supportive husband becomes exasperated with her long hours at work, and in real life, the couple divorced.

The Measuring Man/Green Man

Albert DeSalvo of Malden was picked up by police in 1964 after his photo was identified by several dozen women who had been sexually assaulted in and around Boston. Known by law enforcement as “The Measuring Man” and later “The Green Man,” DeSalvo would go door-to-door complimenting women and asking to measure them, or pretending he was sent to fix a leak. These assaults were separate from the Boston Strangler murders.

One woman reported the incident, and DeSalvo eventually confessed to the police. He was sentenced to prison at Bridgewater State Hospital.

While in prison, DeSalvo shared a cell with convicted murderer George Nasser. Nasser told his lawyer, the famous F. Lee Bailey (who would later successfully defend O.J. Simpson), that he thought DeSalvo was the Boston Strangler. At the same time, news reports raised questions about whether Nasser was the strangler.

The reward

Law enforcement was desperate to make headway on a case reporters were cracking faster than they were. Former Massachusetts governor Endicott Peabody announced a $10,000 reward per case.

Bailey ended up representing DeSalvo, too, and made a deal with Assistant Attorney General John Bottomley that if DeSalvo confessed, it couldn’t be used against him in court. Bottomley agreed to Bailey’s terms, and DeSalvo confessed to being the Boston Strangler in 1975.

But witnesses at Bridgewater say they saw Nasser feeding DeSalvo information, and that both men were eyeing the reward money. DeSalvo was also told he’d get a payout for any upcoming movies or book deals. (Although he never did.)

The politics

DeSalvo’s recorded confession allowed prosecutors to publicly say they caught the Strangler, but he was never charged or convicted of the murders, leaving many feeling unsatisfied with the outcome.

DeSalvo was found guilty of the Green Man crimes in 1967, and sentenced to life in prison.

The phone call

Toward the end of the film, McLaughlin gets a phone call from DeSalvo from jail. He says he has something to tell her, and invites her to visiting hours the next day. But overnight, inmates slipped into DeSalvo’s cell, and he was repeatedly stabbed and killed. Three men were eventually charged.

In reality, it was forensic psychiatrist Dr. Ames Robey who DeSalvo tried to reach the night he was killed.

The killer(s)

In 2015, new forensic DNA evidence linked DeSalvo to the murder of Mary Sullivan, the strangler’s final victim.

“People still ask if DeSalvo was really the Boston Strangler,” Loretta McLaughlin wrote in 1992. “Yes, he was.“