Image caption Albert DeSalvo was never convicted for the Boston Strangler's murders

US authorities say DNA evidence links a dead convict long suspected to have been a notorious serial killer to a woman murdered nearly 50 years ago.

The remains of Albert DeSalvo, who confessed to the Boston Strangler murders, will be exhumed and compared to DNA from the body of Mary Sullivan.

DNA from DeSalvo's nephew matches a sample found on her body, police say.

Authorities say that "familial" match is the first hard evidence DeSalvo was the Boston Strangler.

Sullivan, strangled in her flat in 1964 at age 19, was suspected - but never proven - to be the Strangler's last victim.

DeSalvo, a married father and military veteran, confessed to killing 11 victims attributed to the Boston Strangler, as well as to two other killings.

But he was never convicted of them. Instead, he was sentenced to life in prison over a series of armed robberies and sexual assaults.

Media playback is unsupported on your device Media caption Conley said the DNA evidence would "prove" DeSalvo's guilt

He recanted his confession to the killings before he was stabbed to death in prison in 1973.

Law enforcement officials in Boston have long debated whether DeSalvo was in fact responsible for all of the murders to which he confessed.

Accountability

But now, authorities say tests of a DNA sample taken surreptitiously from a water bottle from which DeSalvo's nephew had drunk is a 99.9% match with DNA retrieved from Sullivan's body and from the blanket on which her body was found.

Suffolk County, Massachusetts, District Attorney Daniel Conley said he expected tests on DeSalvo's remains would show an exact match.

"For almost five decades, the only link between Albert DeSalvo and Mary Sullivan's murder was his confession," Mr Conley told reporters.

"That confession has been the subject of scepticism and controversy from almost the moment it was given.

"These developments give us a glimmer of hope that there can be one day finality, if not accountability, for the families of the ten other women murdered so cruelly in Boston, Cambridge, Lawrence, Lynn and Salem."

Image caption Mary Sullivan, shown in a photo held by her sister and nephew, is the only victim with DNA linked to her case

DeSalvo's relatives say they are furious police tracked DeSalvo's nephew. And Elaine Sharp, a lawyer for DeSalvo's family, says her clients believe that even if there is a 100% match there is still room for doubt.

The lawyer added that private tests revealed other male DNA on Sullivan's body that did not match DeSalvo's.

Officials emphasised that the DNA tests only link DeSalvo to Sullivan's murder. There is no other DNA known to exist for the other victims' cases.

For many years, Sullivan's nephew Casey Sherman believed that DeSalvo was not his aunt's killer, and even wrote a book exploring other possible suspects.

But he said he found the new evidence to be overwhelming.