Cooper's car seat within inches of dad

MARIETTA, Ga. - Unhappy with being a father. Addicted to sexting. Marital infidelity. All possible motives prosecutors planned to offer to jurors when the malice murder and felony murder trial of Ross Harris begins. The Cobb County man faces the gruesome allegation that he intentionally left his 22-month old son to die in a hot car in June, 2014.

But the criminal case could come down to one main question for the jury: how could Ross Harris have not noticed his son on the short drive to work that morning or when he came back to his car later that day?

App users: Click here to watch video report

One month after Cooper Harris died in his dad's hot car, the FOX 5 I-Team watched as Cobb County investigators attempted to reenact those horrible conditions.

On a similar 90-degree day, with Ross Harris' 2011 Hyundai Tucson parked in the same spot near his office, investigators measured the inside temperature rising to as high as 130 degrees according to a law enforcement source.

We immediately noticed just how close Cooper's car seat was to the driver's bucket seat. Cooper's head would have been only inches from his dad, who insisted he forgot he was there.

Lead detective Phil Stoddard offered similar remarks during the 2014 preliminary hearing when talking about their reenactment with a mannequin.

"The head was clearly visible poking up over the car seat," stressed Stoddard.

Father and son would share their final meal together at a Chick-Fil-A only minutes away from Harris' office. What the Home Depot web developer did next made investigators even more suspicious.

Approximately two minutes after Harris put Cooper in his car seat at the restaurant, kissed him and pulled into traffic, Harris insisted he had completely forgotten his son was with him. Instead of turning left near the restaurant to take Cooper to daycare, Harris went straight to his office.

Defense attorneys are expected to argue Harris could have been distracted because evidence shows even during his last meal with Cooper, Ross Harris was texting with women.

Nearly seven hours later, Harris would get back behind the wheel to drive away with the windows still closed. Yet even then, Harris says he did not realize what he had done.

It took more than a mile before Harris claimed he first realized his son was dead in the backseat. But prosecutors have argued the stench inside the car should have been immediate, a smell investigators said they noticed after arriving on the scene that fateful day.

But other experts suggested it would taken much longer for such a smell to materialize and one report raised questions about whether Ross Harris actually had any sense of smell at all.

While many of us say we would never forget our children in a hot car, more than 500 have died just that way since the beginning of this century according to the advocacy group Kids And Cars.

And director Amber Rollins said there has never been a case where someone intentionally left their child in a car to die.