Hollywood, Fla. ? n 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 fliers, 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.”