The Boston Strangler is one of history's longest unsolved murder mysteries.  On Friday, law enforcement officials plan to exhume the body of confessed strangler Albert Desalvo, whose admission years ago was met with skepticism.

WGBH's Phillip Martin looked at the "Boston Strangler" case and explains why this week's developments this may not be the end to the matter. 

On January 4,1964, Bobby Vinton’s single “There I Said It Again” hit the top of the charts, a commuter train collided with a passenger train in Yugoslavia, enemy forces in Vietnam were upgraded in a secret report, and a 19-year-old woman named Mary Sullivan was found dead in her Beacon Hill bedroom by her roommates.

She had been strangled and sexually assaulted. The killer left a card that read “Happy New Year”.

The crime bore a resemblance to the murders of 10 other women of various ages and ethnicities in Boston, Lawrence, Salem, Cambridge, and Lynn. Police were baffled by the case, and the competing egos and jurisdictions made it even more difficult to solve.   

Police finally got a break in October 1964 when a rapist who had posed as a Boston detective was identified as Albert Desalvo. Desalvo, who claimed he had been sold by his own father into slavery on a farm, eventually confessed to the killings. 

Though police believed they had found their man, inconsistencies in his stories made much of what he said inadmissible. He was sent to a Walpole prison on unrelated charges, was killed there, and the mystery of the “Boston Strangler” persisted... until yesterday

At a news conference Thursday, Suffolk County District Attorney Dan Conley announced a major development in the investigation of the homicide of a 19-year-old Mary Sullivan, one of the nation’s oldest murder mysteries.

Conley announced that advances in the sensitivity of DNA testing had allowed investigators to make a familial match between biological evidence uncovered at the crime scene, and a suspect in Mary Sullivan’s murder: Albert Desalvo.

A judge authorized the exhumation of DeSalvo's remains for confirmatory testing that Conley said would prove “once and for all” that DeSalvo murdered Sullivan.

Police were not the only ones pursuing leads and falling short over many decades. Mary Sullivan’s nephew, Casey Sherman, had long doubted that DeSalvo killed his aunt.

For the past 20 years, Sherman said he and his mother had been raising legitimate questions about DeSalvo’s guilt or innocence in the “Boston Strangler” case. DeSalvo’s confession to the murder had raised doubts about his guilt, as it was not consistent with the evidence in the murder.

“I’ve lived with Mary’s memory every day. My whole life,” Sherman said tearfully at the news conference. “I did not know, nor did my mother know, that other people were living with her memory as well. It’s amazing to me today to understand that people really did care about what happened to my aunt.”

District Attorney Dan Conley said investigators used seminal fluid from Sullivan’s body and stains from a blanket at the scene of the crime for DNA testing in the 1990s and the early 2000s, but technology was not advanced enough to make a clear connection between DeSalvo and Sullivan’s murder.

Last year, however, advances in DNA testing allowed investigators to renew testing. Conley said police obtained DNA from a water bottle from which DeSalvo’s nephew drank, and were able to make a familial match between the nephew's DNA and the DNA found on Sullivan’s body and the blanket found at the scene of the crime.

The final confirmation will come from the exhumation of DeSalvo’s body, which is scheduled to happen Friday afternoon.

Not everyone is convinced by the DNA evidence. The DeSalvo family's attorney Elaine Whitfield Sharp said in 2000 independent investigators tested DNA found on a different part of Sullivan's body and did not find a match DeSalvo's DNA. 

But, F. Lee Bailey, the attorney who represented Albert DeSalvo, said he placed a great deal of confidence in the three detectives who interrogated DeSalvo about his confession to the murder and believed it to be true.

The National Institute of Justice provided a $300,000 grant to work on DNA evidence of cold cases that led to this breakthrough. 

As with many mysteries, one step forward in solving the case could also mean several steps backward. This development raises new questions about the 10 other women who were strangled murdered in Cambridge, Boston, Lynn, and Salem between 1962 and 1964. The questions of those will still persists and lingers in the public imagination.