Justin Ross Harris' ex-wife Leanna Taylor still believes son’s hot car death was a tragic accident

— -- The ex-wife of Justin Ross Harris, the Georgia man who was found guilty of intentionally leaving the couple’s 22-month-old son to die in a hot SUV in June 2014, is speaking out for the first time about why she supported her ex-husband through the trial and continues to support him today.

“It never crossed my mind that Ross had done it on purpose,” Leanna Taylor told ABC's Amy Robach in an exclusive interview. “Never. It was an accident.”

A Georgia jury made up of six men and six women in November found Harris guilty on eight counts, including malice murder and two counts of felony murder, for the death of their son, Cooper Harris. He was sentenced to life without parole.

The boy was pronounced dead on June 18, 2014, after authorities said he spent about seven hours alone in a rear-facing car seat in Harris’s locked SUV in the Atlanta area. Temperatures in the area had reached the low 90s outside that day. Authorities ruled that Cooper died of hyperthermia.

Taylor said she first learned something was wrong when she went to Cooper’s daycare that afternoon to pick him up.

“The day care teacher ... said, ‘Well, Cooper’s not here.’ and I thought she was joking, and I was like, ‘No really, where’s Cooper?’” Taylor said. “And she just looked me dead in the face and got my attention. She was like, ‘He’s not here.’ I didn’t know what to think.”

Taylor said her first thought was that someone must have taken him from daycare, and then she said she thought, and admits she said out loud, that Harris must have left him in the car.

“Nothing else that my mind was going to made sense,” she said. “The next place my brain went was, ‘Well, maybe Ross left him at home, like, maybe he just forgot to take him to daycare.’ ... he could be a forgetful person.”

When a detective told her later that day that her son was dead, Taylor said she felt “numb.”

Since 1998, an average of 37 U.S. children have died annually from heatstroke after being trapped inside vehicles, according to the Department of Meteorology and Climate Sciences at San Jose State University, which tracks heatstroke deaths of children in vehicles.

Police say Cooper was in the car when Harris drove to work at a Home Depot corporate office that morning, and when Harris went inside, Cooper was left in the vehicle. Surveillance video showed Harris had returned to his car during lunch to put something away, then went back to work. Later that day, after Harris went back again to his car and drove away from work, then he pulled over in a shopping center parking lot where he asked for help, authorities say.

Authorities argued that Harris going back to the car at lunch proved he knew Cooper was still there, but Taylor sees it differently.

“The going back to the car part actually for me solidifies that it wasn’t intentional,” she said. “To me, it said the opposite, that he didn’t have a clue Cooper was there.”

Detectives zeroed in on Harris, but said they were also suspicious of Taylor because they thought her actions that day seemed strange. She had told daycare workers that “Ross must have left him in the car” and detectives said she seemed unemotional when she was told Cooper was dead.

Most suspicious, police said, was that while Harris was awaiting questioning at the police station, Taylor was recorded asking him, “Did you say too much?” Later, at Cooper’s funeral, eyewitnesses reported that she seemed unemotional, and that she told people Cooper seemed to be in a better place.

Taylor, who was never arrested or charged in the case, said she was just trying to process what had happened.

“Nothing about it felt real. Nothing about it felt like it was happening. It just felt like a bad dream,” Taylor said. “My faith is the only thing that has kept me alive since this happened. The only thing that could give me any kind of peace was knowing that Cooper was in a good place ... People took it as me not wanting him here.

“If I could bring Cooper back to me, of course I would bring him back,” she added.

Since the funeral, Taylor said she has been the target of horrific bullying, both in person and online. She said she was barred at first from getting her son’s belongings from his daycare and she said someone left a note on Cooper’s grave saying, “If you had been my son, I would have loved you.”

“There's no way for someone to know how they would react,” Taylor said. “If somebody had asked me the day before this happened, ‘How would you react if this happened to you?’ My explanation of how I would have reacted and the reality of how I actually reacted would have been completely opposite.”

Because of pretrial publicity, the proceedings were moved nearly 300 miles away from Atlanta to the coastal city of Brunswick, Georgia.

At trial, prosecutors argued that Harris had researched child deaths in hot cars before he left Cooper locked in his SUV all day. They also alleged that Harris was leading a “double life,” having multiple online affairs, including with an underage girl, and argued that Harris’ behavior showed he intentionally killed his son to escape the responsibilities of family life.

“He was living a double life,” assistant district attorney Chuck Boring told “20/20.” “This wasn't just an affair type of thing. It was obsession -- pervasive acts constantly on the internet and meeting up with people ... I think he just was having less and less time with the family to be able to do as much as he wanted and to live the life he wanted.”

Harris’ defense attorneys argued that Cooper's death was an accident and that Harris forgot his son was in the car. Harris pleaded not guilty to the charges, which included malice murder, two counts of felony murder, cruelty to children in the first degree, cruelty to children in the second degree, criminal attempt to commit a felony and two counts of dissemination of harmful material to minors.

Some of the charges referred to sexually explicit text exchanges from March 2014 through the day of Cooper's death that, prosecutors said, Harris had with an underage girl.

Despite the accusations against her ex-husband, Taylor took the stand to testify in his defense. In fact, Taylor said Harris was a very involved father from the moment Cooper was born.

“This was never about me defending Ross,” she told “20/20.” “When you get on the stand and you swear to tell the whole truth and nothing but the truth, that’s what you’re supposed to do, and that’s what I did.”

“I couldn’t get up there and say he was a bad father because it wasn’t true,” Taylor continued. “I couldn’t get up and say that he seemed bothered by having a child because it wasn’t true.”

On the stand, Taylor testified that she was aware that Harris had sexted with other women, that he suffered from a porn addiction, though she claimed she thought it was under control, and said they went to counseling.

“It is incredibly disappointing to see somebody go down -- somebody that you loved, somebody that you trusted, and somebody that you believed in go down a road of that kind of destruction,” she told “20/20.”

Taylor said Harris did apologize to her for what happened and she accepted, but “it’s not going to change anything.” She remains steadfast that Harris never would have killed their son on purpose.

“There was evidence in our relationship that would suggest that he would be capable of being unfaithful to me,” she said. “There was no evidence in our relationship that suggested that he would harm anyone, much less his own son.”

Today, her son Cooper has been gone longer than he was alive. Taylor said she slept with his blankets every night for months and it took her two years before she could bring herself to wash his dirty clothes.

“At this very moment, there is a sippy cup on my kitchen table that still has the water in it that he had drank the day before or the morning of, and I just can’t wash it,” she said. “There’s some of him in it and that may seem weird ... and nobody touches it. It’s like they know better.”

Taylor got a tattoo of Cooper’s right footprint on her right foot so that she said he will always be “walking with her.” She has a second tattoo, a semicolon on her wrist, which has been used as a symbol of suicide prevention. Taylor said she came very close to committing suicide but in the end decided she didn’t want to put her family through more heartache.

Her mission now is to spread awareness about “Forgotten Baby Syndrome,” the clinical term for parents accidentally leaving children in cars, to make sure what happened to Cooper serves as a warning to other parents.

“[Cooper] deserves a better legacy than ‘the boy whose father intended to kill him,’” Taylor said. “People don't believe that it can happen to them, and not believing that it can happen to you is putting your child in danger.”