For nearly four decades, the families of the women murdered by the Boston Strangler believed they knew the identity of the killer: Albert DeSalvo, a factory worker who confessed to the murders.

But new forensic evidence has the family of one of his victims convinced DeSalvo wasn't the infamous strangler.

DeSalvo's son, Michael DeSalvo, said Friday the DNA finding comes after "four decades of pain and shame for my family."

"I'm convinced my father wasn't a killer now, and that's a big weight off my shoulders," he said.

The strangler terrorized the Boston area between 1962 and 1964, killing 11 women. DeSalvo, a blue-collar worker with a wife and children, confessed in 1965 to those murders, as well as two others, but later recanted. He was stabbed to death in 1973 while serving a sentence for rape and other crimes.

One of the victims was Mary Sullivan, who was found murdered in her apartment on Jan. 4, 1964, three days shy of her 20th birthday. State Attorney General Tom Reilly began reinvestigating Sullivan's murder last year at the request of the DeSalvo and Sullivan families.

Sullivan's body was exhumed last year and DeSalvo's six weeks ago. Scientists revealed this week that tests on her clothing and remains found DNA from two individuals other than Sullivan, and neither was DeSalvo.

"We have found evidence, and the evidence does not and cannot be associated with Albert DeSalvo," said James Starrs, a professor of forensic science and law at George Washington University. He has worked on other high-profile forensics cases, including the Lindbergh baby kidnapping, the Lizzie Borden hatchet murders and the outlaw Jesse James.

"I, as a juror, would acquit him with no questions asked," Starrs said Thursday.

The evidence appears to clear DeSalvo only of sexual assault, but Starrs and other forensic scientists who took part in the investigation said it also raises significant doubt that DeSalvo killed Sullivan.

A prosecutor who worked on the original strangler investigation in the 1960s said the new DNA tests do not prove that DeSalvo is innocent of Sullivan's killing or any of the other slayings.

"It doesn't prove anything except that they found another person's DNA on a part of Miss Sullivan's body," said Julian Soshnick. "I believe that Albert was the Boston Strangler."

Soshnick, who interviewed DeSalvo twice after he confessed to the killings, said he asked him specifically about the Sullivan case and seven or eight of the other murders.

"There were things that only the killer would know that were not known publicly," he said. "We knew a lot more than was made public, and he knew them."

Specifically, Soshnick said, DeSalvo described accurate details about what type of ligatures were used and how he tied them around the victims' necks.

DeSalvo family attorney Elaine Whitfield-Sharp said Friday that DeSalvo knew murder details only because his lawyer, F. Lee Bailey, fed him information through leading questions. Bailey did not immediately respond to a call for comment.

DeSalvo never was charged in the killings, and those who question whether he was responsible point to a string of circumstances that raise doubts about his involvement. Among them: There was never any physical evidence putting him at the crime scenes; he did not match witness descriptions of possible suspects; and he was never on investigators' lists of more than 300 suspects.

"If he didn't kill Mary Sullivan, yet he confessed to it in glaring detail, he didn't kill any of these women," said Casey Sherman, Sullivan's nephew. The DeSalvo and Sullivan families believe DeSalvo may have confessed in hopes of making money from book and movie deals.

Reilly said in a statement that the new findings don't resolve the question of whether DeSalvo killed Sullivan.

Reilly repeated a call for the DeSalvo family to provide a DNA sample from a family member so investigators can conduct further tests. The family has refused to do so until Reilly's office turns over crime scene evidence.

"Tom Reilly, stop hiding behind the shadow of the past and do your job," said Dan Sharp, an attorney for the DeSalvo and Sullivan families.

He said he knew of no plans to exhume other bodies.

DeSalvo's family also wants to clear up the circumstances of his death. Three inmates were tried for the killing, but a jury failed to reach a decision in one trial, and a mistrial was declared in another. Prosecutors had said they believed the men were trying to keep DeSalvo from entering the prison drug trade.