A Queensland prisoner who scalded schoolboy Daniel Morcombe's killer with a bucket of boiling water has been sentenced to three years' jail.
Adam Paul Davidson, 31, pleaded guilty in the Brisbane District Court on Monday to torturing Brett Peter Cowan at the Wolston Correctional Centre on August 5, 2016.
Judge Ian Dearden sentenced Davidson to three years' jail but with time already served he will be released on parole in late November.
The court heard Davidson plotted and watched Cowan's movements for a month to find the best way to harm the high-profile sex offender.
Prosecutor Mark Whitbread said Davidson got the idea to use boiling water after he saw another inmate with horrific scars and wearing a burn suit after a similar attack.
"He would love that scarring to be on Cowan," Mr Whitbread said.
The court heard Davidson poured a mop bucket over Cowan's head while the then 46-year-old was playing cards with other inmates.
He then struck Cowan in the head with the bucket three to four times.
Daniel Morcombe disappeared in December 2003, aged 13, while going Christmas shopping. Source: AAP
Cowan received superficial burns to 15 per cent of his body and was treated in hospital to prevent infection.
Davidson told investigators he attacked Cowan "for a little bit of retribution" and he wanted him "to feel the pain like someone like Daniel Morcombe has felt".
"I did it. Only me no one else was involved. He had it coming, he's a f***king grub," Davidson said.
Judge Dearden said every person was entitled to be treated respectfully, no matter how appalling the crimes they had committed.
"We are all precious human beings, it doesn't matter who we are," Judge Dearden said.
"You have no entitlement to act as a vigilante."
Cowan, 48, is serving a life sentence for abducting and murdering Daniel on the Sunshine Coast in December 2003.
The 13-year-old's remains were found in August 2011 after an elaborate police operation prompted Cowan to confess and lead undercover officers to where he dumped Daniel's body.
