The mother of two little girls who died in a hot car parked outside their home is the first person to be charged under Queensland's new definition of murder.

Kerri-Ann Conley, 27, was on Saturday charged with two counts of murder after her one and two-year-old daughters died inside a black station wagon at their home in Logan.

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This year, the Queensland government passed laws which expanded the legal definition of murder - an offence which carries a mandatory life sentence.

Now, an act can be considered to be murder if the death is caused by "reckless indifference" to human life.

Queensland Law Society president Bill Potts said the law changes mean a person who commits "an act of negligence" could "find themselves treated as if they ... intended to kill".

"Eventually, a Supreme Court jury is going to have to look at this to see whether the actions of a person who's been charged amounts to reckless indifference," he said.

Sentences 'not sufficient'

The laws were introduced following controversial manslaughter cases in Queensland.

"There's been a concern in the public that sentences for manslaughter were not sufficient," Potts said.

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Conley's matter was heard in Brisbane Magistrates Court on Monday when she was remanded in custody on two counts of murder and two drug-related charges.

Her daughters were declared dead at the scene and police say they showed signs of being exposed to extreme heat.

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