Darcey-Helen, 2, and Chloe-Ann Conley, 18 months, died on November 23, 2019 at Waterford West, south of Brisbane after the car they were in reached an estimated temperature of 61.5C.
Their mother, Kerri-Ann Conley, had left them in the car outside her home since 4am after returning from a drive to a friend's place and using the drug methamphetamine.
Conley pleaded guilty in February 2023 to two counts of manslaughter and was sentenced to nine years' jail to be eligible for parole in November 2024.
Peter Jackson said he called Child Safety four to six times in the two weeks before the girls died. (Jono Searle/AAP PHOTOS)
The inquest in Brisbane on Tuesday heard from Detective Sergeant Ty Williams, who watched numerous hours of footage from Conley's security camera system as part of a Queensland Police investigation into the two girls' deaths
A police timeline of the footage noted Conley left her vehicle at 4.11am without taking the girls with her about six minutes after parking in her home's yard and returning to them at 1.16pm.
"Upon exiting the dwelling, CCTV depicts Kerri-Ann lighting a cigarette casually before walking down the steps and identifying that the children were still in the vehicle," Det Sgt Williams said.
He testified that Conley later told him she woke up at 1.15pm then brought the girls inside and put them under a shower to cool them off before contacting Darcey's father, Peter Jackson, and contacting triple zero.
A police report stated Conley turned off her security camera system's video recorder just over 10 minutes after finding the girls in the car.
"Once Kerri-Ann returns to the dwelling (for a second time) the CCTV stops," Det Sgt Williams said.
Mr Jackson also testified on Tuesday and said he called the Queensland Department of Child Safety four to six times in the two weeks before the girls died but "to no avail".
"My concern (was) about the drug use around Darcey and Chloe. I also informed them of the (meth pipe and small clipseal bags) I found just walking through the house, the utter pigsty the house was in ... to no avail. Nobody seemed to be listening," Mr Jackson said.
The hearing was briefly adjourned after Corrective Services accidentally showed a camera feed to the court of Conley as she listened to the proceedings remotely from custody.
The inquest heard Child Safety also received a notification concerning Darcey's welfare after Mr Jackson brought her to hospital because he suspected she had been exposed to meth.
Mr Jackson said Conley told him she had bought synthetic urine in an attempt to test negative. (Jono Searle/AAP PHOTOS)
A doctor told the department on November 3, 2019 that Darcey did not have signs of intoxication based on a general examination without a blood or urine test.
The doctor also recorded Mr Jackson's concerns at the time.
"Mr Jackson reported seeing pipes and needles in the house. The father has been advised Ms Conley is using methamphetamine in the house regularly," the doctor stated.
Mr Jackson said one of the first calls he made was about a text message he received from Conley in late October 2019.
"I got Chloe in the car. Woke up at 2am. Left Chloe in the car. Oops," Conley's message stated.
Mr Jackson said he responded like anyone else would to such a message.
"I responded to the effect of 'what the f***?' I was a little taken aback," Mr Jackson said.
He said he had seen Conley attempt to flush drug traces from her system and she told him she had bought synthetic urine in an attempt to test negative.
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