The toddler who died in his father's hot SUV in the US last month had been switched out of his forward-facing new car seat weeks before his death.
Cooper Harris was found dead in his rear-facing car seat in a parking lot in Cobb County, Georgia on June 18 - after sweltering inside for more than seven hours.
His father, Ross Harris, faces a murder charge in the boy's death - but insists he mistakenly left his 22-month-old son inside the car before heading to work.
The parents had bought a new, forward-facing child seat just six weeks earlier but they switched back to his old seat for reasons that are not yet clear.
Suspicions are also growing about what role Harris' wife may have played in the death, the Daily Mail reported.
Leanna Harris has not yet been charged with any crime but she expressed little emotion throughout Thursday’s hearing, despite a number of shocking allegations including that her husband had been sexting with six different women, some teenagers, on the day their young son died.
When reunited with her husband at police headquarters after he had been charged with murder, Leanna Harris asked him: "Did you say too much?" according to Cobb County Police Detective Phil Stoddard.
When she called home with the news of Cooper’s death, her mother could be overheard on the phone saying: "Why aren’t you crying? Why aren’t you reacting?"
Her response, according to Detective Stoddard: "I must be in shock."
The detective said after the boy died, Harris showed no emotion while being interviewed by investigators.