The chilling true story behind serial killer film Boston Strangler

Watch: Boston Strangler trailer

The chilling true story of the Boston Strangler, one of America's most notorious serial killers, has been turned into a new Disney+ film.

Keira Knightley and Carrie Coon star as Loretta McLaughlin and Jean Cole, the pioneering reporters who covered the story in the early 1960s.

The true-crime thriller, simply titled Boston Strangler, is out on the streaming platform today. Here's everything you need to know about the real case.

Who was the Boston Strangler?

The Boston Strangler was a serial killer who murdered at least 11 women in the US city from 1962 to 1964.

Most of the victims were sexually assaulted and strangled with articles of their own clothing, mostly their nylon stockings. The killer was given several nicknames by the press, including the 'Phantom Fiend', the 'Phantom Strangler' and the 'Mad Stranger of Boston', as the crimes sent shockwaves through the city and made national headlines.

The youngest and final victim, Mary Sullivan, was 19 when she was raped and murdered in her apartment, just days after moving to Boston. The oldest victim, Mary Mullen, was 85.

Read more: The best movies new to streaming this weekend

Albert DeSalvo, a factory worker and military veteran, confessed to being the killer in 1965, when he was held in a psychiatric ward after being charged with an unrelated rape.

However, police lacked the evidence to bring him to trial, and he was never convicted of the murders. According to the Associated Press, DeSalvo did not match witness descriptions of the attacker, and was not on investigators' lists of more than 300 suspects.

In 1967, he was jailed for life at a maximum-security prison for a string of armed robberies and sexual assaults. He later recanted his confession to the 11 killings, and was fatally stabbed in his cell by another inmate in 1973.

The mystery of the killer's identity lingered for decades, and police reopened the case in 1999 in an attempt to get closure for the victims' families. The remains of DeSalvo and victim Mary Sullivan were exhumed in 2001 for DNA testing.

Forensic scientists found no DNA match until 2013, when new technology finally linked DeSalvo to Sullivan's killing.

Martha Coakley, the then-attorney general of Massachusetts, said: "This leaves no doubt that Albert DeSalvo was responsible for the brutal murder of Mary Sullivan, and most likely that he was responsible for the horrific murders of the other women he confessed to killing."

Despite the breakthrough a decade ago, the full case may never be solved. Similar DNA was not recovered from the scenes of the other murders, meaning there is no conclusive proof that DeSalvo was responsible for all the killings.

Daniel Conley, the then-district attorney for Suffolk County, said at the time: "These developments bear only on Mary Sullivan's murder. They don't apply to the other 10 homicides popularly attributed to the Boston Strangler. Even among experts and law enforcement officials there is disagreement to this day about whether they were in fact committed by the same person."

Who were Loretta McLaughlin and Jean Cole?

The new film Boston Strangler focuses on two female reporters, Loretta McLaughlin and Jean Cole, who covered the story for the Boston Record American newspaper. The pair, portrayed by played by Knightley and Coon, battled sexism from police and colleagues to uncover the truth about the killings.

The film's director and writer Matt Ruskin, who grew up in Boston, told Empire magazine: "I always loved journalism stories and in researching the case, I discovered these two journalists, starting with Loretta McLaughlin, the first journalist to connect the murders, and in her reporting, she actually gave the Boston Strangler his name.

"It was a really monumental story for her in her career in the early 1960s. She was a very ambitious reporter in a male-dominated field and this was a real turning point for her. In reading about Loretta and her partner Jean Cole, the other reporter she worked with, I discovered that Jean Cole's granddaughter is an old friend of mine."

McLaughlin died aged 90 in 2018 and Cole died aged 89 in 2015, but the film has the blessings of both their families.

Ruskin says the journalists' relatives welcomed him "with open arms" as he researched the murder cases, sharing press clippings and old photos with him.

"So at that point, I was really hooked and devoted to telling their stories," he said.

Boston Strangler is streaming on Disney+ now.