A father and son, who tortured, murdered and burnt the remains of Gold Coast drug dealer Shaun Barker, have been sentenced to life behind bars.

The 33-year-old was last seen alive in December 2013.

His charred remains were found in a forest near Gympie four months later.

A jury found William Francis Dean guilty of Mr Barker's murder, torture and interfering with his corpse in March 2017.

Shaun Barker (pictured) was last seen in December of 2013 before his remains were found scattered throughout a forest just outside Gympie, Queensland four months later

Stephen John Armitage and his son Matthew Leslie Armitage were also convicted of torture and interfering with his corpse, but it took a retrial in September for the pair to also be found guilty of killing him.

Brisbane Supreme Court Justice David Jackson said, in sentencing on Wednesday, questions about the exact injuries inflicted on Mr Barker and what ultimately killed him could not be answered because there were no witnesses.

Throughout the two trials, the court heard evidence he had been kept in one of Stephen's commercial fishing eskies, denied food and water and tied to a tree.

There were also reports his bones had been broken and his genitals had been covered in honey to attract ants.

Stephen John Armitage (pictured) was sentenced to life in prison for the savage torture and murder of Gold coast drug dealer Shaun Barker

Justice Jackson said while it was difficult to know how reliable some of the evidence given during both trials was, he said the trio inflicted 'severe pain and suffering' on their victim.

'Shaun Barker was being tortured to provide some kind of information, probably about drugs, that the defendants ... thought he had taken,' he said.

His body was later burnt in a fire pit, before his bones were scattered in the forest.

Matthew Leslie Armitage (pictured) was also sentenced to life behind bars alongside his father, Justice Jackson said Mr Barker was being tortured 'to provide some kind of information, probably about drugs'

Justice Jackson said it was likely the Armitages and Dean did that to cover up his death.

The trio was sentenced to life in jail for Mr Barker's murder and also received prison sentences for the torture and interference with a corpse charges, to be served concurrently.

They will be eligible for parole after they have served 20 years behind bars.