One of America's most notorious child murder cases was finally solved yesterday after a 27-year saga that led to the dead boy's father becoming the nation's leading anti-crime crusader.

John Walsh, host of the television show America's Most Wanted, wept as police in Florida announced that his six-year-old son Adam was killed by Ottis Toole, a cannibalistic drifter who died of liver failure in 1996 while serving life sentences for seven other murders.

“For 27 years we have been asking: ‘Who could take a six-year-old boy and murder him and decapitate him? Who?' Now we know who,” Mr Walsh said at a press conference in Hollywood, Florida. “The not knowing has been a torture but that journey's over ... Today is a wonderful day. We can end this chapter of our lives.”

Since the boy's disappearance during a shopping trip with his mother, Revé, in 1981, and the discovery two weeks later of his severed head in a canal 125 miles away, Mr Walsh and his wife have been high-profile advocates for victims' rights and spurred new legislation to change the way in which missing children's cases are handled. They founded the National Centre for Missing and Exploited Children (NCMEC), launched a “Code Adam” programme for helping children lost in department stores and helped to get the faces of thousands of missing children on to milk cartons and shopping bags.

Their activism led to the creation of child fingerprinting programmes, new safety codes for schools and the creation of missing persons units at every majorbig police department in the country. In 2006 they stood on the South Lawn of the White House to watch President Bush sign into law the Adam Walsh Child Protection and Safety Act, which instituted tougher penalties for crimes against children and established a national database of child predators.

“The tragedy of Adam Walsh shook a nation to its core ... and fundamentally changed the way America addresses the problem of missing children,” said a statement from the NCMEC, calling it the most high-profile child abduction case since the kidnap and murder of the aviator Charles Lindbergh's 20-month-old son in 1932.

Through America's Most Wanted, launched in 1988, Mr Walsh has also taken the stories of countless missing children into millions of homes each week, helping to reunite many missing children with their families and prompting the capture of more than 1,000 fugitives. Yet, until now he was unable to get justice for his own son, whose case was dogged by police bungling, investigative failures and repeated confessions and then retractions by Toole.

Only with the appointment last year of Chief Chad Wagner at the Hollywood Police Department, who undertook a personal review of the case, did it take a positive turn. “This investigation had flaws,” Chief Wagner admitted yesterday, issuing a personal apology to the Walsh family as they clutched each other's hands and wiped away tears. “For years we took a defensive posture on this case rather than sealing the deal with Ottis Toole as we should have done.

“In three decades of investigation, Ottis Toole has been the suspect - from confessions, to sightings, to witness interviews, it's all there and I think it was time to sit back and say: 'Why do we want to keep denying what we really think is the suspect - Ottis Toole',” Chief Wagner said.

Mr Walsh said: “Some big, bad mistakes were made but for us it ends here.” He added: “I'm not about revenge. I never have been. I believe wherever Ottis Toole is, he's paying and being held accountable ... I believe that Ottis Toole is probably getting what he deserves, somewhere.”

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