HOLLYWOOD, Fla. -- In the end, there was no smoking gun, no new evidence, not even anyone police could charge. All they had was what was right in front of them the whole time.

And, so, on Tuesday investigators finally closed the 27-year-old case of a little boy whose gruesome killing helped spur improvements in finding missing children and catapulted his father to fame as the host of "America's Most Wanted."

"For 27 years, we've been asking who can take a 6-year-old boy and murder and decapitate him. We needed to know. We needed to know," said John Walsh, the father of Adam, the victim. "The not knowing has been a torture, but that journey's over."

Police said the man long considered the lead suspect, Ottis Toole, was conclusively linked to the murder, but largely with circumstantial evidence that they've had all along. And it came far too late: Toole died in prison more than a decade ago.

"Our agency has devoted an inordinate amount of time seeking leads to other potential perpetrators rather than emphasizing Ottis Toole as our primary suspect," said Hollywood Police Chief Chadwick Wagner. "Ottis Toole has continued to be our only real suspect."

Wagner acknowledged numerous missteps in the investigation and apologized to the boy's parents, John and Reve Walsh, who long ago derided the probe as botched.

For all that went wrong, the case contributed to massive advances in police searches for missing youngsters and a notable shift in the view that parents and children hold of the world.

Adam's death, and his father's transformation from a hotel developer to an activist, 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. And it prompted national legislation to create a national center, database and toll-free line devoted to missing children, and, of course, "America's Most Wanted," which brought those cases into millions of homes.

"In 1981, when a child disappeared, you couldn't enter information about a child into the FBI database. You could enter information about stolen cars, stolen guns but not stolen children," said Ernie Allen, president of the Center for Missing and Exploited Children, which was co-founded by John Walsh. "Those things have all changed."

Jim Larson of Orlando has witnessed first-hand the effects of Walsh's work. His wife Carla was abducted in a grocery store parking lot one afternoon in 1997 and was raped and strangled. He credits "America's Most Wanted" with catching her killer.

"Maybe, eventually, they would have gotten there," Larson said of police. "But it seemed like right after the show aired, calls were coming in and leads were followed and they got him."

The man convicted in the killing, John Huggins, is now on Florida's death row.

Others are more hesitant to credit John Walsh with good. His efforts, said Mount Holyoke College sociologist and criminologist Richard Moran, have made children and adults exponentially more afraid.

"He ended up really producing a generation of cautious and afraid kids who view all adults and strangers as a threat to them and it made parents extremely paranoid about the safety of their children," Moran said.

Adam disappeared on July 27, 1981. His mother left him playing in the toy department at a Sears store at a Hollywood mall, but didn't find him when she returned. Over the loudspeaker, the plea sounded: "Adam Walsh, please come to customer service."

Two hours after the disappearance, police were called. His mother and grandmother searched the mall in a growing panic and John Walsh tried to work with uniformed officers to find his son.

Two weeks passed before the boy's fate was learned. Fishermen discovered his severed head in a canal 120 miles away near Vero Beach; his body never was 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 became actively 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."

Still, on Tuesday the Walshes said they felt they had finally gotten what they long sought.

"We can end this chapter of our lives," John Walsh said. "It's not about closure. It's about justice."