Man who plead guilty to killing four-year-old stepson smiles and laughs leaving court

Matthew Scown plead guilty to manslaughter and was sentenced to a maximum four years in jail.

The remainder of his sentence was suspended, having already spent two years and eight months in custody. Scown's former de facto partner, Heidi Strbak, is also charged with manslaughter.

Tyrell died in 2009 from an abdomen injury caused by at least one blunt force trauma, but an autopsy revealed he had also suffered 53 bruises and 17 abrasions.

Justice Martin Burns told the court it is not suggested Scown knew about or inflicted the fatal blow on the little boy, but said Tyrell would have been 'in extreme pain.'

'The horror of all of this is that the injuries Tyrell sustained were treatable,' Justice Burns said, acknowledging that Scown had asked Stbak to seek medical attention for Tyrell on the day he died.

'Clearly you were very worried about the little boy,' he said. 'You ought to have acted yourself, regardless of her wishes.'

Queensland Premier Anna Palaszczuk has slammed Scown for his behaviour when leaving court.

'How insensitive is that for the man to be laughing after the death of his stepson, it's absolutely unacceptable, she said.

'I understand that his partner is due to face court shorltly, and I hope that she feels the full force of the law.'