"What you are going to see here in this trial is that responsible is not the same thing as criminal," the lawyer said. "The evidence will show that Ross loved that little boy more than anything. Cooper's death was an accident. It was always an accident, and that is what he told the police over and over again."
Harris wept as Kilgore presented his case.
Among the witnesses the defense plans to call is Harris' ex-wife, Leanna Taylor, a woman who "has every reason in the world to hate that guy, to despise that guy," but who will testify that Harris was a good father who deeply loved Cooper, Kilgore said.
Harris, 35, is standing trial in south Georgia, roughly 300 miles away from his Marietta home in suburban Atlanta, after a judge granted a change of venue. He has pleaded not guilty to charges of malice murder, two counts of felony murder and first-degree cruelty to children in the toddler's June 2014 death.
On Monday, Cobb County Assistant District Attorney Chuck Boring told jurors that Harris is a philanderer and manipulator who wanted to be free of his family so he "could move on to his other life."
"On that day, when his child was cooking to death, he was messaging a girl, 16, to get vaginal pictures from her," the prosecutor said.
Yes, he was an adulterer
Judging from Boring's opening statement, Harris' adultery will be key to proving the state's allegation that he knew Cooper would die when Harris left him in his vehicle while he went to work. In addition to sexting the teen, Boring said, Harris had chats with five other females while his son was dying in a rear-facing car seat.
Kilgore conceded, though, that Harris was unfaithful to his wife and regularly sexted with women. While that makes Harris many things, Kilgore said, it doesn't make him his son's murderer.
"You are going to hear about very embarrassing sexual matters and sexual language, and he has earned every bit of that shame. But Ross' sex life, no matter how perverse and nasty and wrong we think it is, it has nothing to do with the fact that he forgot that little boy, " the defense lawyer said. "The sexual behavior is not some kind of motive to murder a person he loved more than anything in the whole world."
Observers are justified in being disgusted, Kilgore said. Through the lens of hindsight, it's easy to be disgusted by a man texting women at work while leaving his toddler in a vehicle for hours on a summer day in Georgia, Kilgore said. (Records show that the mercury topped 92 that day.)
"But it doesn't change the fact that at the time he did it he was clueless," he said.
Kilgore said some of the prosecution's most vilifying allegations actually support the defense assertion that Harris forgot the boy was in the back seat.
For instance, he said, If Harris were intentionally seeking to kill Cooper, why wouldn't he purge his phone of all the damaging sexts he had sent to other women? Not only did Harris fail to delete anything, he engaged in more "terribly incriminating, nasty, adulterous stuff," Kilgore said.
'None of them knew his personality'
Kilgore also addressed claims by investigators and prosecutors regarding Harris' behavior before and after Cooper's death. A detective has repeatedly alleged Harris looked up information on hot-car deaths, while Boring, the prosecutor, mocked Harris' reaction to learning his son had died, likening him to comedic actor Will Ferrell.
To Boring's claim that Harris didn't behave like a grieving father when he pulled into a parking lot after discovering Cooper has been left in the car, the defense attorney said Harris "tried to do CPR but he couldn't focus. He is desperately trying to get somebody on the phone."
"The state is right about one thing: Ross is responsible for the child's death. He is responsible, there is no doubt," Kilgore said. "When he glanced over the shoulder and looked at Cooper, he knew what he had done. He pulled over to a parking lot and pulled him out desperately. He was overwhelmed and couldn't concentrate."
Kilgore said Harris was "hysterical" when he realized that he had left Cooper in the car -- a claim the attorney said witnesses and police would corroborate -- and he questioned the basis for Boring's conclusion.
"None of them knew his eccentricities. None of them knew his personality, his coping mechanism for trauma," Kilgore said of police who interviewed Harris.
The attorney showed video of a distraught Harris crying, "What have I done?" in a police interrogation room. Harris further asked for God's forgiveness, spoke how much the loss hurt and asked to trade places with Cooper, Kilgore said.
"That man sitting over there may have been an adulterer, but he was devastated by the loss of his son," the lawyer said.
'He loved that little boy more than anything'
As for allegations that Harris performed suspicious Internet searches, such as how long it takes a child to die in a car and what the temperature needed to be, Kilgore flatly said, "This was something that was made up by the Cobb County Police Department."
To the contrary, some of Harris' Google searches suggest he was "planning for a future with his son," his attorney said. Harris looked up family vacations and reached out to a travel agent, and he researched child passport rules, new homes and good school districts, Kilgore said.
Key to proving his client's disposition, Kilgore said, will be ex-wife Leanna Taylor.
"There is one person in this world who has every reason in the world to hate that guy, to despise that guy, because that guy over there, Ross Harris, he took everything from her. He cheated on her. He humiliated her in front of the whole world. He is responsible for the death of her only little boy. She ought to hate him. She ought to despise the heck out of him and nobody would blame her," he said.
Kilgore expects Taylor to paint Harris with not-so-kind words, he said. She'll likely speak of his philandering ways, their wrecked marriage and how he didn't take care of their only child on that hot June day.
"But she is also going to say, 'Ross Harris loved that little boy more than anything in the world.' She is going to tell you he was a wonderful father. The woman who's got every reason in the world to despise his guts, she is going to speak the truth. She's going to tell you they got it wrong," Kilgore said.
'Ross must have left him in the car'
Before Monday's opening arguments, the judge in the case impaneled a half-male, half-female jury and tapped two men and two women to serve as alternates.
The case stems from a June 18, 2014 tragedy in which Harris, then 33, strapped his son Cooper into a carseat and drove to a Chick-fil-A for breakfast. Harris then drove to the Home Depot corporate headquarters nearby, where he worked, rather than first dropping Cooper off at daycare, according to the charges.
Sometime after 4 p.m., as Harris drove to a movie theater to see "22 Jump Street" with friends, he noticed his son was still in the car, Harris told police.
Harris pulled into a shopping center parking lot and pulled Cooper's lifeless body from the car. His screams attracted a crowd, some of whom called 911. Others attempted to administer first aid.
Witnesses said Harris was hyperventilating and screaming. In the meantime his then-wife, Leanna Harris (now Leanna Taylor), was already headed to the daycare to pick up Cooper. When she learned Cooper had never arrived, witnesses said she came to an immediate conclusion.
"Ross must have left him in the car," she's reported as saying
. "There's no other explanation. Ross must have left him in the car."
At 10 p.m. that day, Justin Ross Harris was arrested. An autopsy later confirmed that Cooper died of hyperthermia.