The jurors in the trial of a US man accused of intentionally leaving his toddler to die in a locked car over seven agonising hours have been asked a series of shocking questions.

Justin Ross Harris faces multiple charges, including murder, in relation to the death of 22-month-old Cooper in an unventilated SUV at the carpark of his Georgia office on June 18, 2014.

Harris, who is widely known as the "hot car dad", claims he forgot his only son was in the vehicle when he drove to work on that piping hot day.

However, prosecutors will allege Cooper's death was no accident but all part of a grand plan by Harris to get out of an unhappy marriage so he could pursue his love of young girls.

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Two of the eight counts against him relate to dissemination of pornography against minors.

Harris admitted under police questioning to having researched "child deaths inside vehicles and what temperature it needs to be" after detectives examined his computer.

Police discovered Cooper's mother Leanna had also looked up child deaths in cars but she was never charged and there is no suggestion she was in on her former husband's alleged plot.

The pair divorced last year.

Court commentators believe the outcome of this largely circumstantial murder case hinges on jury selection. To that effect, more than 250 potential jurors were today asked to complete a 17-page document containing dozens of personal questions, some relating to sex, pornography and their love life.

They ranged from the startling "Have you ever had sexual addiction?", "Have you looked at a pornographic website?" "Have you ever had an extramarital affair?" to more mundane questions like, "Do you have a child that rides in a car seat?" "Have you watched any legal documentaries or docudramas?" and "Have you ever driven a Hyundai Tucson?"

The questions stem from allegations that Harris was sexting underage girls, having extramarital affairs and also researched hot car deaths and a child-free lifestyle.

Prosecutors say Harris was messaging up to six women the day Cooper died, and reportedly told one woman on the app Whisper: "I love my son and all but we both need escapes".