By Rich McKay

ATLANTA (Reuters) - A Georgia jury was set to begin deliberations in the case of a man charged with murdering his son by leaving the toddler in a sweltering car, after prosecutors said on Monday the man allowed the boy to suffer so he could be free of his marriage and child.

Lawyers for Justin Ross Harris, 35, told the jury on Monday the death his 22-month-old Cooper in June 2014 was an accident. Deliberations were planned to start on Tuesday morning and if convicted, Harris could face life in prison.

"You'll have to do some mental gymnastics to find Ross guilty of anything," defense attorney Maddox Kilgore said in closing arguments, noting that Harris was planning a future with his wife and son.

Cooper died after being locked in Harris' SUV outside his workplace in suburban Atlanta.

Harris wept openly in the courtroom as his attorney played a home video of Cooper laughing as Harris taught him to play a guitar.

In their closing arguments, prosecutors said Harris drove to work with the child and "with his selfish, malignant heart, left him there to die," Cobb County Assistant District Attorney Chuck Boring said.

More than 1,000 pieces of evidence were presented in court, including text messages that were part of the prosecution. One of those messages was sent by Harris about 10 minutes before he left the car with the boy inside the car and it read: "I hate being married with kids. The novelty has worn off and I have nothing to show for it."

The court heard about Harris' trail of extramarital affairs and encounters with prostitutes and how he sent sexually charged texts and naked pictures to women and underage girls.

The defense contends Harris drove straight to work after a father-and-son breakfast at a Chick-fil-A, instead of taking a U-turn toward the child's day care. Whatever Harris' sexual sins, this case was no different than many other parents who forgot a child in a car, his lawyers said.

His former wife testified that Harris "ruined her life," but would never have intentionally harmed his son.

About 70 witnesses, including a prostitute, several teenaged girls, friends, co-workers, detectives and experts testified during the six-week trial.

The proceedings were moved to Brunswick, Georgia, some 300 miles (500 km) from suburban Atlanta, after the court failed to seat an impartial jury last spring.

(Editing by Jeffrey Benkoe and Bernadette Baum; Writing by Jon Herskovitz and Alistair Bell)