Does DNA prove Albert DeSalvo is the Boston Strangler?

The question of who sexually assaulted and murdered 55-year-old Anna Slesers and 10 other women in the Boston area over 19 months in the early 1960s has been debated for decades.

Now a new lead could help put the case to rest after forensic evidence linked Albert DeSalvo – the man who confessed to the murders but was never prosecuted for them – to the final victim of the serial killer who became infamous as the Boston Strangler.

DeSalvo was stabbed to death in prison in 1973. Officials in Boston said his body would be exhumed after DNA testing showed a “familial match” between DeSalvo and evidence from the body of Mary Sullivan, the 19-year-old woman who was the last of the Boston Strangler’s victims. She was raped and murdered in January 1964. Ms Slesers, a Latvian seamstress who lived in Boston’s 19th-century Back Bay neighbourhood, was the killer’s first victim. She was found by her son on 14 June 1962, the belt of her blue bathrobe tied around her neck.

In and around Boston, women were warned by police to lock their doors and windows and be wary of strangers. Countless hours were spent poring over evidence and hundreds of potential suspects were questioned. The victims’ ages ranged from 19 to 85.

In 1965, DeSalvo, who at the time was in a psychiatric hospital, is said to have confessed to his cellmate, who went on to inform a lawyer. Although DeSalvo’s confession reportedly included details about the killings that were not widely known, there was no physical evidence connecting him with the crimes. He was later jailed for life in connection with other crimes, including a string of sexual assaults.

DeSalvo became known in the popular imagination as the Boston Strangler, but questions about his confession continued to linger after his death. Some experts have even suggested that the killings might have been the work of multiple murderers, not an individual. Among those questioning DeSalvo’s account of what happened during those 19 months in the early 1960s was Casey Sherman, the nephew of Ms Sullivan, the serial killer’s final victim. Mr Sherman expressed doubts about the confession. Moreover, a decade ago, the bodies of Ms Sullivan and DeSalvo were exhumed and tested. DNA tests at the time did not produce a match.

“Everybody who’s taken an independent look at this case and doesn’t have dogs in the fight believe that there are serious doubts,” he told The Boston Globe in 2012.

But police believe they might now finally have the evidence they need to connect DeSalvo to Ms Sullivan’s murder. The new lead, which police attributed to “the miracle of science and DNA evidence”, came when officials obtained a bottle discarded by one of DeSalvo’s descendants.

Forensic evidence from the bottle showed a “familial match” to a preserved semen sample found on Ms Sullivan’s body, leading the police to ask a judge to authorise the exhumation of DeSalvo’s body for further testing.

While questions still remain unanswered – the new link only connects DeSalvo to Ms Sullivan, not the other victims – the breakthrough is significant.

“There was no forensic evidence to link Albert DeSalvo to Mary Sullivan’s murder until today,” Daniel Conley, the Suffolk County District Attorney, told reporters in Boston.

Mr Sherman was present at the briefing. He thanked officers for persisting with the case and said: “I only go where the evidence leads.”

Timeline: The investigation

14 June 1962 55-year-old Anna Slesers is found strangled to death in the first killing attributed to the serial murder who became known as the Boston Strangler.

4 January 1964 19-year-old Mary Sullivan is the killer’s final victim. She is found raped and murdered in her Boston apartment.

1965 29-year-old Albert DeSalvo confesses to the 11 killings, including the murders of Ms Slesers and Ms Sullivan, that police believe might be linked. But there is no physical evidence to connect him to the murders. He is later sentenced to life in prison for other crimes.

1973 DeSalvo is killed in prison.

2000-01 A forensic investigation, including tests on the bodies of DeSalvo and Ms Sullivan, do not show any links.

11 July 2013 Officials announce that DeSalvo’s body will be exhumed after new technology shows a “familial match” between DNA from one of his descendants and preserved evidence taken from Ms Sullivan’s body.