DANIEL MORCOMBE: PRISONER SENTENCED TO THREE YEARS FOR BOILING WATER ATTACK ON BRETT PETER COWAN

PHOTO Brett Cowan was attacked in August 2016 while playing cards with other inmates.

A prisoner who tortured Daniel Morcombe's killer in a "vigilante act" in a Brisbane jail has been sentenced to three years' imprisonment.

Brett Peter Cowan is serving a life sentence for the 2003 murder of the 13-year-old Sunshine Coast schoolboy.

Adam Paul Davidson, 31, pleaded guilty in the District Court in Brisbane today to torturing Cowan in August 2016 by pouring boiling water from a mop bucket over him and then striking him with it.

Davidson has served almost 11 months in custody for the attack and is due to be released on parole next month.

Prosecutor Mark Whitbread told the court Davidson attacked Cowan from behind while he was playing cards with other inmates, with the intention to hurt but not kill him.

"He immediately tipped the bucket over the complainant's head," he said.

"[Cowan] felt extreme pain ... he started screaming and stood up."

The prosecutor said Davidson later admitted to the crime to officers and described it as "a vigilante act on behalf of Daniel Morcombe".

"I did it ... he had it coming. He's a f***ing grub," the court heard Davidson told officers.

Cowan was treated in hospital for superficial burns to 15 per cent of his body.

The attack occurred at the Wolston Correctional Centre in Wacol, west of Brisbane.

In sentencing, Judge Ian Dearden quoted Mahatma Gandhi.

"An eye for an eye makes the whole world blind," he said.

"His punishment is to be in prison, not to be the subject of physical, mental or other abuse.

"People can never be entitled to take the law into their own hands.

"You have no entitlement to act as a vigilante."