BOSTON – DNA tests confirm that the man who once claimed to be the Boston Strangler did kill the woman believed to be the serial killer’s last victim and was likely responsible for the deaths of the other victims, authorities said Friday.

Albert DeSalvo admitted to killing Mary Sullivan and 10 other women in the Boston area between 1962 and 1964 but later recanted.

The DNA finding “leaves no doubt that Albert DeSalvo was responsible for the brutal murder of Mary Sullivan” and it was “most likely” that he also was the Boston Strangler, Massachusetts Attorney General Martha Coakley said.

Eleven Boston-area women between the ages of 19 and 85 were sexually assaulted and killed between 1962 and 1964, crimes that terrorized the region and grabbed national headlines.

Authorities said recently that new technology allowed them to test semen left at the crime scene of Sullivan’s death using DNA from a living relative of DeSalvo’s. That produced a match with DeSalvo that excluded 99.9 percent of suspects, and was the first forensic evidence tying DeSalvo to the nearly 50-year-old case.

To confirm the match, investigators unearthed his remains a week ago and said Friday that the odds that the semen belonged to a male other than DeSalvo were 1 in 220 billion.

An attorney for DeSalvo’s family, Elaine Sharp, said last week that even a perfect DNA match wouldn’t mean he killed Sullivan and suggested that someone else was present at the slaying. She said previous private testing on Sullivan’s remains showed the presence of DNA from what appeared to be semen that wasn’t a match to DeSalvo.

Police said the evidence used in private testing from Sullivan’s exhumed remains was “very questionable.”

Sharp also said that DeSalvo’s brother and his nephew — whom police secretly trailed to collect a family DNA sample from a discarded water bottle — won’t comment on the new DNA result because it hasn’t been proven to be relevant to the question of whether DeSalvo raped and strangled Sullivan.

But the idea that the DNA match doesn’t identify DeSalvo as Sullivan’s killer is bizarre, responded Jake Wark, a spokesman for Suffolk District Attorney Daniel Conley.

“It suggests that Mary Sullivan had consensual sex with Albert DeSalvo moments before another person who has never been identified sexually assaulted and strangled her to death, leaving no trace of his presence,” Wark said.

F. Lee Bailey, a defense lawyer who once represented DeSalvo, said Friday that DeSalvo provided so many details that only the perpetrator would know that he became convinced that his client was the Boston Strangler.

Bailey said it’s fortunate that the DNA test was run because the failure to try DeSalvo for the 11 homicides led to speculation about the Strangler’s identity. He said Friday’s announcement shows that case detectives did good police work when they devised questions for DeSalvo that only the killer could answer correctly.