But, finally, the end is firmly in sight.

The parents of Daniel Morcombe, the 13-year-old Sunshine Coast boy who was killed on December 7, 2003 – 11 years ago next month – were on Thursday left to wait for the outcomes of two concurrent appeals.

Brett Peter Cowan, the man convicted in March of murdering their son, has appealed his conviction on the basis that his taped confession "circumvented" his right to silence, and that his trial judge erred in her directions to the jury.

At the same time, the Crown argued Cowan's sentence – life with a non-parole period of 20 years – was "manifestly inadequate" and must be increased.

On Thursday afternoon, Mr and Mrs Morcombe trod the all-too-familiar path out of the Brisbane Supreme Court building, where the appeals were heard on Wednesday and Thursday.

"We won't say anything now, but yeah, we're good," Mr Morcombe said as he left the court.

"It's over."

While the hours, the days, the weeks and months in court rooms may be over for the Morcombes, the wait remained for the court's final decision.

The two-day hearing at the Court of Appeal in Brisbane, presided over by Chief Justice Tim Carmody, Justice Margaret McMurdo and Justice Hugh Fraser, heard Cowan's defence team argue their client had been "tricked" out of his right to silence.

Peter Davis, QC, for Cowan, on Thursday said his client's rights had been "circumvented" by undercover police, posing as underworld figures, who solicited a taped confession out of him.

Mr Davis said without that confession, the Crown had no case against his client.

But even with that confession, Mr Davis said the Crown needed to prove not only that the confession was made, but also that it was true.

Mr Davis said a big factor in the jury's decision to convict would have been the fact that Cowan led police to Daniel's final resting place, which would have appeared to add credence to his confession.

"We don't shy away from the fact that the fact Mr Cowan took police to a place on the Sunshine Coast where evidence was found," he said.

But Mr Davis said it was possible Cowan knew the location through other means, namely communication from convicted paedophile Douglas Jackway, to convicted criminal Leslie McLean, and from McLean to Cowan.

Mr Davis said the trial judge erred by not raising that possibility in her summary to the jury because, if it had any doubt about how Cowan knew the location, "all of a sudden it's a completely different case".

"Unless there's some doubt in the jury's mind about how Mr Cowan came to know about the location of the evidence found on the Sunshine Coast, then adding his knowledge to the confession, the case is very strong," he said.

"But there was an explanation, and not a bad one."

Mr Davis said Cowan had a right "not to convict himself from his own mouth", which was a critical factor in the defence's case.

"It was his right to do (not make admissions), police knew that was his right and they circumvented it," he said.

Chief Justice Carmody asked Mr Davis if Cowan's previous declarations that he would not make any admissions meant Cowan could not change his mind in the future.

"That's not what happened," Mr Davis said.

"He continued through vigorous cross examination at the (coronial) inquest, through interviews...the one thing he did constantly was he didn't admit to persons of authority that he killed Daniel."

After the Justices were asked to consider whether to quash Cowan's conviction, they were asked to consider whether to increase his sentence.

Counsel for the Attorney-General Tony Moynihan, QC, said Cowan's guilt had been properly and appropriately proven at his trial and it was now up to the Court of Appeal to ensure he was appropriately punished.

Cowan received the mandatory life sentence for Daniel's murder, with a non-parole period of 20 years – an increase of five years from the normal 15-year non-parole period.

Mr Moynihan told the court that was "manifestly inadequate".

"(Cowan) killed a child, which is a matter that society rightfully regards with absolute abhorrence," he said.

"He intentionally killed a child to avoid detection.

"He abducted a child waiting for public transport and whether it be for a child to go to school, or to go to the shops, that attacks at the heart of our way of life.

"The evil and monstrous nature of the killing needs to be deterred, be denounced and, as (Daniel's) family indicated, (the sentence) does not in any way facilitate the administration of justice."

But Angus Edwards, QC, for Cowan, said increasing the non-parole period by more than five years was unprecedented in murder cases with just the one victim.

Mr Edwards said Max Sica, whose non-parole period was extended to 35 years, and Scott Maygar, who was jailed for at least 30 years, had multiple victims.

Sica murdered his ex-girlfriend Neelma Singh and her two younger siblings, Kunal and Sidhi, in 2003.

In May 2005, Maygar killed 17-year-olds Ty Wilson and David Lyons, along with 30-year-old Michael Thompson, in a brutal evening in Toowoomba.

Mr Edwards says Cowan was convicted of killing just the one person, Daniel Morcombe.

"(Those cases) involved the killing of at least three people," he says.

The Court of Appeal has reserved its decision.