Conley, 30, of Waterford West, pleaded guilty in Brisbane Supreme Court this week to two counts of manslaughter and was sentenced on Thursday.

Justice Peter Applegarth said Conley had shown “gross criminal neglect” as her daughters’ sole custodian at the time and had made the “inexcusable” decision to leave the children in the car.

Conley had taken her daughters Darcey-Helen, aged two-and-a-half, and Chloe-Ann, 18 months, to her friend’s place at 11.30pm on November 22, 2019 and returned home at about 4am the next day.

Conley left the children in the car seats because she did not want to wake them and went inside her home to sleep.

“You decided to leave the children in the car for a completely inadequate reason … it was not a momentary lapse,” Applegarth said.

The car was left in direct sunlight with no shade and all doors and windows closed, leading to the car reaching an estimated temperature of 61.5C by 10.30am.

“They were uncared for, unheard and unobserved in the dark. The sun had risen by 5am and did you check if the children were crying or upset? No, you did not. You were on your phone until 5.55am,” Applegarth said.

He said he could not bear to think about the possibility of the children suffering in the car for hours.

“Their skin was blistered, they were dehydrated. One can only hope they succumbed early in the morning,” he said.

When Conley returned to the car she found the children dead and took them out of the car before trying to dispose of drugs in her house.

She called Darcey-Helen’s father, Peter Jackson, as well as an ambulance and told paramedics she had fallen asleep but gave a false account of her movements to police when they arrived.

Conley also pleaded guilty this week to possessing cannabis and a drug smoking pipe and had admitted to using methamphetamine the day before her daughters’ death and passing out when she got home the next day,

“No child should have a mother who uses methamphetamine. You told an undercover police operative that your children always came first. That is a statement only a drug addict could make,” Applegarth said.

“Meth also comes first in that race … in this case it led to the death of two young girls.”

He said Conley had told the truth that she told police she was an “exhausted single mother who did not have the support that she needed”.

Jackson was in the court on Tuesday and Thursday to hear what Applegarth described as the distressing and graphic details of his daughter’s death.

Speaking briefly outside court, he said he was “obviously not happy with the sentence”.

“I can’t help what the other parent does. You can’t always be around, unfortunately,” he said.

“I miss their laughs, their giggles, everything. They’re toddlers, what’s not to love about them?”

The judge noted that Conley had an abusive childhood and been diagnosed in custody with a major depressive disorder and psychosocial stress from guilt resulting in nightmares and feeling like she was “eating herself alive”.

“I accept you are remorseful and not a day goes by that you don’t think about the death of your daughters and the effect this had on others,” he said.

He said Conley’s meth use was ultimately the cause of her daughters’ deaths and she had failed to learn of its effects on her parenting from previous drug convictions and had left her children in the car on previous occasions.

Conley has already spent nearly three years and three months on remand, most of which was spent in protective custody, and Applegarth declared that period as time served.

She will be eligible for parole after November 22, 2024.

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-AAP