Justin Ross Harris
Justin Ross Harris, 33, of Marietta, Georgia was charged with murder and second-degree cruelty to a child over the death of his 22-month-old son, Cooper.Reuters

The father of the toddler left to die inside a hot car was "sexting" up to six different women while his son perished in 30C heat, a court has heard.

Cobb County Police Detective Phil Stoddard said Justin Ross Harris, 33, sent explicit messages, including naked photographs, to women while his 22-month-old son, Cooper, was left in searing temperatures in a baby seat in the back of his Hyundai Tucson in Georgia.

Stoddard told Cobb County Magistrate Court that Harris, who denies charges of murder and second-degree cruelty to a child, had also been leading a "double life" with "alternate personalities".

He also detailed evidence that suggested Harris actually wanted to kill his son, as he allegedly looked at an article on news website Reddit which advocated living child-free, and twice watched a video about children dying in cars.

His wife, Leanna Harris, told investigators they watched the video as a precaution because they had read a story about the dangers of leaving a child inside a car in the heat.

The couple had two life insurance policies for the toddler, one for $2,000, (£1,170), and one for $25,000, (£14,500), according to investigators.

Harris also apparently searched "how to survive prison" on the web before Cooper died.

His defence lawyer, Maddox Kilgore, said: "We've heard a lot of suggestions, speculations, coincidences ... but you certainly haven't heard any evidence this was intentional.

"There's no evidence Harris was aware the child was in the car. Why would he bring his colleagues right up to the car. It doesn't make any sense."

On 18 June, Harris stopped for breakfast at a fast-food outlet on his way to work while his son Cooper was left strapped at the back of his SUV.

Witness Leonard Madden told the court he saw the "precious boy, lying there, lifeless."

"The father, had just given his child CPR," he said. "Two other people had come near. As I got closer you could just hear his cries and his desperation for his son to be revived."

A judge denied Harris bond and he remains in jail until he appears in court again on July 15.