After 27 years, Florida police say they have finally solved the brutal murder of six-year-old Adam Walsh -- a crime that inspired the boy's father to become the host of "America's Most Wanted."

Police in Hollywood, Fla., said that Ottis Toole, a notorious serial killer who died in prison in 1996, killed the young boy in 1981.

"It's not about closure ... it's about justice," said the boy's father John Walsh during an emotional press conference on Tuesday.

Toole was considered the prime suspect in the case, and at one point, he even confessed to the crime. However, since Toole confessed to hundreds of murders, police eventually ruled him out.

But John Walsh said he always believed that Toole -- a drifter who murdered at least four people -- was responsible for the killing.

"For 27 years, we've been asking, who could take a six-year old and murder and decapitate him?" said John Walsh.

In a deathbed confession, Toole told to his niece that he had killed the boy. The niece later told Walsh about the confession.

"We needed to know. We needed to know. And today we know. The not knowing has been a torture, but that journey's over."

Police declined to say what evidence was used to link Toole to the killing, but they said that no DNA proof was available.

After the killing, officers found a pair of green shorts and a sandal at Toole's home, which were similar to items worn by Adam before his death.

While serial killer Jeffrey Dahmer was once considered a possible suspect, Hollywood police Chief Chadwick Wagner said Tuesday that Toole is the only plausible culprit.

"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 Wagner.

The young Walsh disappeared from a mall in his home town of Hollywood on July 27, 1981. Two weeks later, the boy's head was found in a canal about 200 kilometres away.

No other body parts were ever found.

Police also admitted Tuesday that officers made several key mistakes during the crucial early stages of the investigation.

For instance, a piece of blood-stained carpet which police took from Toole's car was lost during the investigation, meaning officials couldn't test it for DNA evidence, and even the car itself.

While John Walsh has criticized police for bungling the investigation, he praised them Tuesday for finally closing the case.

"This is not to look back and point fingers, but it is to let it rest," he said.

While the murder remained an unresolved tragedy for the Walsh family, it pushed John Walsh into activism.

He created the National Center for Missing and Exploited Children, which put the faces of missing children on milk cartons and changed the way police investigated missing kids.

But Walsh's activism also led to a kind of mass paranoia about the safety of children in the greater society, said criminologist Richard Moran.

"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."

With files from The Associated Press