"Who could take a 6-year-old and murder and decapitate him? Who?" an emotional John Walsh said at Tuesday's news conference. "We needed to know. We needed to know. And today we know. The not knowing has been a torture, but that journey's over."
Walsh's wife, Reve, at one point placed a small photo of their son on the podium.
The suspect, Ottis Toole, had twice confessed to the killing, but later recanted. He claimed responsibility for hundreds of murders, but police determined most of the confessions were lies. Toole's niece told the boy's father, John Walsh, her uncle confessed on his deathbed in prison that he killed Adam.
Many names have been mentioned in connection to the case in the years since the killing, including serial killer Jeffrey Dahmer, but Toole's has persistently nagged detectives. John Walsh has long said he believed the drifter was responsible, saying investigators found at Toole's home in Jacksonville a pair of green shorts and a sandal similar to what Adam was wearing.
The Walshes long ago derided the investigation as botched. Still, he praised the Hollywood police department for closing the case.
"This is not to look back and point fingers, but it is to let it rest," he said.
Adam Walsh went missing from a Hollywood mall on July 27, 1981. Fishermen discovered his severed head in a canal 120 miles away two weeks later. The rest of his body was never found.
Authorities made a series of crucial errors, losing the bloodstained carpeting in Toole's car - preventing DNA testing - and the car itself. It was a week after the boy's disappearance before the FBI got involved.
"So many mistakes were made," John Walsh said in 1997, upon the release of his book "Tears of Rage," which harshly criticized the Hollywood Police Department's work on the case. "It was shocking, inexcusable and heartbreaking."
For all that went wrong in the probe, the case contributed to massive advances in police searches for missing youngsters and a notable shift in the view parents and children hold of the world.
Adam's death, and his father's subsequent activism on his behalf, helped put faces on milk cartons, shopping bags and mailbox flyers, started fingerprinting programs and increased security at schools and stores. It spurred the creation of missing persons units at every large police department.
It also prompted national legislation to create a national center, database and toll-free line devoted to missing children, and led to the start of "America's Most Wanted," which brought those cases into millions of homes.