Michelle Nguyen, 21, is facing a charge of manslaughter over the death of her daughter Thy Tran in a car outside her house in November last year.
After returning home, Nguyen left Thy asleep in the vehicle, with its doors and windows closed, parked in direct sunlight in the driveway.
Nguyen returned 15 minutes later to check the baby, and, finding her still asleep, went back inside and sat in the lounge room, intending to check again in another 15 minutes.
Instead, she fell asleep, waking in a panic at 2pm with the realisation her daughter was still in the car.
Nguyen called emergency services but Thy was pronounced dead at the scene.
Paramedics recorded the baby’s body temperature at 41.5 degrees.
Bureau of Meteorology records showed the temperature in Glenroy rose from 26 to 28 degrees between noon and 3pm on November 5. Heat tests inside the car in the driveway on a later day with similar weather conditions found the temperature rose from 26.8 degrees to 47.9 degrees within 90 minutes.