A father who forgot his baby was in the back of his car, a dad who beat his daughter so severely she had brain damage and his partner who desperately tried to take her to the hospital would be treated the same under mandatory sentencing, the Attorney-General argues.
Ms D'Ath argued against mandatory sentencing while introducing Labor's child killer laws on Tuesday, sharing details of two manslaughter cases.
In the first, a little girl, not even two months old, had four of her ribs broken by her father, her arm fractured and skull fractures so severe that she received brain damage.
The mother tried to seek medical treatment for the girl but her abusive partner actively discouraged her from calling an ambulance.
Over seven to 10 days, the mother repeatedly suggested taking the child to the hospital but he refused.
Unfortunately, when the mother, a victim of domestic violence, took the girl to the hospital, it was too late and her baby could not be saved.
With medical intervention, their daughter would have lived.
In the second case, a father forgot his nine-month-old child was in the back of his car and left her unattended for several hours.
She died of dehydration and the father was greatly distressed at the scene and afterwards when he realised what had happened.
All three parents, including the mother, entered pleas of guilty to manslaughter.
Ms D'Ath said a "fair-minded person" could not reasonably argue all three should be sentenced to the same mandatory minimum penalty of 15 years in jail.
"The mother, who pleaded guilty to manslaughter on the basis that she did not obtain medical assistance for her child quickly enough, in a domestic and family violence context, would be sentenced potentially to 15 years jail under the LNP's proposed mandatory regime for manslaughter," she said.
"The same as her partner who violently assaulted her child and showed a callous disregard for their child's needs."
Ms D'Ath said mandatory sentencing for child manslaughter was a simplistic approach to a complex issue.
"These examples demonstrate the unacceptable injustice that would follow if this Parliament were to legislate for a minimum mandatory sentence for manslaughter," she said.
However, the LNP has argued Ms D'Ath got it wrong.
The opposition plans to introduce a private member's bill with an offence of child manslaughter on Wednesday, which would attract a mandatory 15-year jail penalty.
An LNP spokeswoman said their new offence would only target people who intentionally killed children.
LNP Shadow Attorney-General David Janetzki said any claim opposition's bill would capture accidental deaths was false.
"Without mandatory sentencing, Labor’s laws aren’t worth the paper they are written on," he said.
LNP leader Deb Frecklington has described Labor's laws as "soft".
The LNP has proposed a new offence of child manslaughter that would include a mandatory 15-year jail penalty.
The LNP would also increase the minimum non-parole period for the murder of a child from 20 to 25 years.
Labor's laws would redefine murder to include the unlawful killing of another if the death was caused by an act or omission with reckless indifference to human life.
It would add an aggravating factor to manslaughter of a child under 12, which would increase the lengths of sentences.
The bill would also increase the maximum penalty for the offence of failure to supply necessaries from three years imprisonment to seven years.
Family members of slain toddler Hemi Goodwin-Burke and Tiahleigh Palmer were in the public gallery as the bill was introduced. The average jail sentence for child manslaughter in Queensland is 6.8 years, compared with 8.5 years for an adult.