DNA tests have proved that the man thought to have been the Boston Strangler killed the last of the 11 victims of the 1960s serial killer, officials said on Friday.
Albert DeSalvo was never convicted of the rapes and murders of 11 women carried out in Boston between June 1962 and January 1964.
He was stabbed to death in prison in 1973 while serving time for other sex offenses, having earlier confessed to a fellow prisoner that he was the Strangler.
Recent advances in DNA technology made it possible for investigators to match samples from a DeSalvo relative to semen found at the scene of the January 1964 rape and murder of 19-year-old Mary Sullivan.
That led to DeSalvo's body being exhumed for definitive tests, the results of which were made public on Friday.
"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," said Massachusetts Attorney General Martha Coakley.