Investigator Neil Purtell told Radaronline compelling evidence that linked the serial killer to the 1981 murder of six-year-old Adam Walsh had been bungled by Florida police.
Mr Purtell interviewed Dahmer in prison after he was sentenced to life in prison for the murder of 17 boys and men in Wisconsin.
“He said if he did admit to it, he would be killed in prison as a paedophile,” Mr Purtell told RadarOnline. “My impression was he was admitting he did it.”
Adam was abducted from a Sears department store in the Hollywood Mall in Florida in 1981. His severed head was found 16 days later in a canal 120 miles away, and the case became one of the most infamous child murders in American history.
In 2008, Florida police announced they had concluded that convicted serial killer Ottis Toole was responsible for the gruesome murder.
Toole had confessed to the killing before recanting, and died in prison in 1996. Police failures in the search for Adam and lost evidence meant that police were unable to secure a conviction against Toole.
Investigators found that Dahmer had been living in Miami Beach at the time, and two witnesses placed him near the Hollywood Mall on the day of Adam’s abduction.
Mr Purtell was one of the first law enforcement officers to arrive at Dahmer’s Milwaukee apartment after his arrest, and says he immediately saw parallels to Adam Walsh’s murder.
Dahmer publicly denied any involvement in Adam’s murder, and authorities eventually ruled him out.
In a 1992 interview, Dahmer said: “I’ve told you everything—how I killed them, how I cooked them, who I ate. Why wouldn’t I tell you if I did it to someone else?”
Mr Purtell’s claims come on the heels of a new Netflix dramatisation of the Dahmer saga, Monster: The Jeffrey Dahmer Story. A journalist who broke the story in 1991 spoke to The Independent earlier this week about what the series got wrong.
The murder of Adam Walsh stunned America, and led to a total overhaul in the way missing child cases were investigated.
Speaking about his son’s murder in 2008, John Walsh said he was convinced that Toole had been responsible.
“The not knowing has been a torture. That journey’s over,” he said.
“A lot of horrible memories in this police department looking for that little boy. Now I think it’s only fitting that it ends here, in this police department.”
John Walsh founded the Adam Walsh Child Reform Centre with wife Reve and became a tireless advocate for missing person cases, appearing in dozens of TV commercials warning parents to not let children out of their sight.
He went on to host America’s Most Wanted from 1988 to 2012 and was responsible for apprehending more than 1,000 criminals.
In 2006, on the 25th anniversary of Adam’s disappearance, George Bush signed the Adam Walsh Child Protection and Safety Act, which established a national database of child sex offenders.
Toole, who was found guilty of a slew of unrelated killings, lived near the mall where Adam disappeared.
Later, behind bars, he confessed to Adam’s murder several times, but Hollywood police refused to believe him as he had a reputation for trying to claiming murders with which he had no association.