The third week of testimony of the hot car death trial of Cobb County dad Ross Harris began Monday

Harris is accused of intentionally leaving his son in his hot SUV to die.

On Monday, the jury heard testimony from an underage girl Harris allegedly sexted with. She said the relationship began when she posted, "I love older guys" on the social app Whisper. Prosecutors said the 15-year-old told Harris that she was 18. Harris sent the teen a selfie from a bathroom, and later a picture of his genitalia. The teen sent Harris a sexually-explicit picture of herself, she said, and then confessed that she was only 15 years old.

"He wanted me to make him a naughty old man," she said.

While that testimony was not broadcasted, testimony from another woman was.

Jacqueline Robledo, who was 19 at the time she allegedly had sex with Harris, testified about their interactions and the information they shared with each other.

Photos | Ross Harris trial day 7, Oct. 17

Robledo said she also met Harris on the social app Whisper and began a friendship. She testified that they met up in the summer of 2013 to have sex at his apartment. After that they allegedly kept up an online friendship.

She also testified that Harris told her he hooked up with a man while on vacation in 2014. He allegedly me that man on the Whisper app also.

Ross Harris is facing several charges, including malice murder and felony murder, in the death of his son, Cooper. The 22-month-old was found dead in the back of an SUV back in June 2014.

Photos | Meet the players in the Ross Harris hot car death trial

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