A three-year-old boy could not be saved after being found in his parent's car outside a shop in Glenfield in Sydney's southwest on February 2, 2023.
In a separate incident almost two years later, a 14-month girl was found deceased in a car outside her daycare in Earlwood in the city's inner west.
Both died of heat exposure because of their fathers' accidental memory failures, coroner Rebecca Hosking found on Monday.
"These are circumstances which can occur to the most caring, loving parent, of which all of them were in this case," she said.
During a two-day inquest into the deaths in April, the court heard evidence from Professor Muireann Irish, a cognitive neuropsychologist.
She explained how tired parents could form an intention to do something such as drop their children off at daycare.
However, they could then form a false, reconstructed memory after completely forgetting to do so.
While this often occurs in harmless situations such as going shopping and forgetting to buy milk or leaving car keys at home, sometimes these memory lapses could have more tragic consequences, Judge Hosking said.
In the case of the three-year-old boy, his father was tired after staying up late the evening before and had his ordinary morning routine interrupted by a trip to the petrol station to fill up.
He returned home to work without dropping his son at daycare, leaving the child in the car all day while temperatures soared to 31C.
It was only until after he had picked up his eldest son from primary school and been to the shops that he realised his mistake.
"I thought I dropped him off," the father told police after the incident.
"'We opened the door and I couldn't believe my eyes that he was sitting in his car seat."
It was a similar experience for the father of the 14-month-old girl, who forgot to drop her off at daycare after taking his wife to the train station.
He had been running late and was frazzled due to heavier-than-normal traffic.
When he went to the daycare centre that afternoon, believing he had dropped her off earlier, he found her unresponsive in the back seat.
"He was screaming, he got her out of the car and tried to wake her up," Judge Hosking said.
"An ambulance was called but it was too late."
She recommended the NSW Department of Education promote greater public awareness campaigns around children being left in hot vehicles.
Any campaigns should include that parents of young children were particularly susceptible to this type of memory lapse, the coroner said.
Parents and carers could adopt cues to assist such as placing their children's belongings on the front seat as reminders, she added.
Judge Hosking recommended adding information about children and hot cars to the Blue Book given to parents after the birth of a child and also to the Department of Infrastructure's website.
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