A drug-addicted father who abandoned his baby son at a boat ramp south of Brisbane has been sentenced to 12 years in jail for manslaughter.

Key points: Justice Peter Applegarth called Shane Arthur Simpson's offending a "gross negligence of an extreme kind"

Justice Peter Applegarth called Shane Arthur Simpson's offending a "gross negligence of an extreme kind" Two-year-old Baden Bond was left near the Logan River at dusk in May 2007

Two-year-old Baden Bond was left near the Logan River at dusk in May 2007 Baden's mother, Dina Colleen Bond, was sentenced to three years in prison

Shane Arthur Simpson left his two-year-old son Baden Bond near the Logan River at dusk in May 2007 because he was tired of looking after him.

The child's body was never found but the Supreme Court heard on Thursday he probably drowned.

The boy's mother, Dina Colleen Bond, was also sentenced to three years in prison for being an accessory to manslaughter because she covered up the crime.

Baden Bond was last seen in at a property in Woodridge, south of Brisbane, in 2007. ( Supplied: Queensland Police Service )

She was eligible for release from custody on Thursday after serving almost two years in prison.

The court has previously heard Simpson had a long-term addiction to methamphetamine that was "particularly intense" in 2007 when he abandoned Baden.

Simpson, 51, was originally charged with murder but pleaded guilty to the lesser offence of manslaughter.

Final moments 'full of fear'

In sentencing, Justice Peter Applegarth called the offending a "gross negligence of an extreme kind".

"Having abandoned him so callously and in such danger and having driven off, you did not turn around 10 minutes later or return to the area that night to remove Baden from danger," he said.

"You had ample time to reflect on your actions and the high risk that Baden would die before anyone found him.

"You went home and got on with your life."

Sorry, this video has expired Justice Applegarth called Simpson 'callous' in his sentencing remarks

Justice Applegarth called the abandonment "planned", adding there was no suggestion Simpson was on drugs at the time he left his son.

Instead of abandoning him at a relatively safe place like a school or hospital, Justice Applegarth said Simpson "practically invited a tragic end to his life".

His final moments would have been "full of fear".

Simpson refused to tell police who the child was "given to" when they called on him in 2016. ( AAP )

"Even abandoning him beside the main street of Beenleigh would have given him a better chance of survival," Justice Applegarth said.

"He would, at least, have stood a chance at being spotted and made safe by a passing citizen."

'Staying with relatives'

The court heard Bond and Simpson had a history of hostility with the Queensland Department of Child Safety, who took Baden into care just after his birth in 2005 because the baby had drugs in his system.

The toddler was released back into his parents' care in October 2006.

Flowers and teddy bears left outside a Woodridge house in March 2016. ( ABC News: Casey Briggs )

The court was told Centrelink was advised in May 2007 that Baden was no longer in his parents' care but no notification was made to the department.

Bond and Simpson told officers he was staying with relatives. When they came to do checks at the home, the child was not there.

Department officers drove past the house again in August 2007 but it was locked and vacant because the pair had moved to NSW.

The NSW child safety department began focusing their attention on the missing child in September 2015, but Simpson told them Baden was travelling with relatives around Western Australia.

When NSW police came to the parents' home in March 2016, Simpson told them: "I gave him to someone, it's none of your business … I don't have to tell you, to who."

Outside the court Detective Inspector Damien Hansen said Baden had been robbed of his childhood.

"That's what someone does to get rid of a pet they don't want — to do it to a two-year-old child is inhumane, and the lack of a remorse I think sums it up," he said.

Simpson will be eligible for parole after serving 80 per cent of his sentence behind bars.