Twenty years behind bars isn't long enough to punish serial sex offender Brett Peter Cowan for the "evil" murder of Daniel Morcombe, a court has heard.
Queensland's attorney-general has appealed against Cowan's sentence for murdering schoolboy Daniel Morcombe, arguing it's inadequate and fails to protect the community.
The appeal on Thursday immediately followed Cowan's own legal challenge to his murder conviction, with both being heard in the Court of Appeal in Brisbane.
Daniel's long-suffering parents Bruce and Denise Morcombe must wait to learn Cowan's fate after Supreme Court Chief Justice Tim Carmody and Court of Appeal Justices Margaret McMurdo and Hugh Fraser reserved their decisions on both appeals.
Their judgment, on Cowan's appeal at least, is not expected until next year.
The 45-year-old was convicted of Daniel's murder in March and sentenced to life imprisonment with a non-parole period of 20 years - five years above what was then mandatory for murder.
The mandatory custodial murder sentence has since been raised to 20 years.
Director of Public Prosecutions Tony Moynihan QC, for Attorney-General Jarrod Bleijie, said Cowan's sentence was plainly unreasonable considering his crime and criminal history.
"He abducted a child waiting for public transport and ... that attacks at the heart of our way of life," Mr Moynihan told the court.
"The evil and monstrous nature of the killing needs to be deterred and denounced and Daniel's family vindicated, and it (the sentence) did not in any way facilitate the administration of justice."
Mr Moynihan added Cowan was a serial violent sex offender who displayed a "complete lack or remorse" for his offending, and the sentence wouldn't protect the community from the "real" danger he represents.
In answer Cowan's barrister Angus Edwards said the request for a harsher punishment was "simply insupportable" and far out of step with other murder sentences.
Earlier, during an appeal spanning one-and-a-half days, Cowan's legal team argued their client hadn't be granted a fair trial and should be acquitted or granted a retrial.
Their main argument was that Cowan's confession, made to police posing as gangsters, was given involuntarily and under threat, and therefore was inadmissible evidence.
Top barrister Peter Davis QC said police, aided by the coroner, unfairly denied Cowan his right to silence by tricking him into confessing in what amounted to an abuse of process.
It was further argued there had been a miscarriage of justice because the trial judge didn't give proper weight to certain defence evidence in her instructions to the jury.
Daniel's parents said there had been "a lot of talk" without much substance and they were confident Cowan's conviction would be upheld.
"We maintain that the trial was conducted properly and the verdict was sound and we maintain faith on that," Bruce Morcombe told reporters outside court.
Their son was 13 when he was abducted while waiting for a bus on the Sunshine Coast hinterland in 2003.
