Qld police expect Morcombe case debate

Queensland's Police Commissioner Ian Stewart says debate about how long it took to arrest and convict schoolboy Daniel Morcombe's murderer, a known pedophile, will rage for the next decade.

A jury has found Brett Peter Cowan guilty of indecently dealing with 13-year-old Daniel, killing him and interfering with his body in December 2003.

But former Queensland police officer Kenneth King has told the ABC there were flaws in the investigation that saw detectives focus on a blue car instead of searching the house of Cowan, who had previously been convicted of child sex crimes.

Mr Stewart declined to say if Cowan should have been arrested earlier.

"That issue is going to be the debate for the next 10 years and I suspect there's going to be books and films made of this investigation," he told reporters in Brisbane on Friday.

"Look, I'll leave that decision up to the public to make.

"Police work is about meticulous, rigorous process to make sure when we do get the evidence, it'll stand to the scrutiny that is required for arrest and will ultimately lead to a court case."

Cowan, a 44-year-old father of three, was arrested in August 2011 after he told undercover police posing as members of a criminal gang that he had killed Daniel in the Sunshine Coast hinterland.

Asked whether Cowan, with his history of child sex convictions, should have been on the streets in 2003, Mr Stewart said: "Now that his history has come out more broadly, I think there are people who have to answer that question, but it's not us."

Cowan had previously served jail time for raping boys in Brisbane and Darwin in 1987 and 1993.

The commissioner said police were the victim of their own success given the fact their covert police operation was revealed to the Supreme Court jury that convicted Cowan.

"The more widely it's known, the less effective it becomes," he said.

Police Minister Jack Dempsey said he thought officers and detectives had done an outstanding job to bring Cowan to justice.

"They have gone above and beyond the normal call of what police officers are called on to do," he said.

"All Queenslanders are rightfully proud of the work the police have done in this particular investigation."

Mr Dempsey said the Queensland government would be introducing tough new sex offender legislation to parliament in an attempt to prevent another person like Cowan from preying on children.

Federal Attorney-General George Brandis praised authorities for bringing Cowan to justice.

"I think Australians, and Queenslanders in particular, will breathe a sigh of relief that he's behind bars," he told reporters in Sydney.

"No doubt he will stay there for many, many years to come."

Senator Brandis was also asked why Cowan was free despite his history of abuse.

He said that was a matter for state law and that people were entitled to the presumption of innocence.