Harris was accused of intentionally leaving his 22-month-old son, Cooper, in a hot car to die in 2014. Harris has maintained he simply forgot his son was inside of the vehicle.
Prosecutors argued Harris wanted to leave his family, showing explicit messages he sent to young women and girls. However, the Georgia Supreme Court took issue with that evidence - but the prosecutor, Jesse Evans, said he stands by it.
Evans said they built the case against Harris methodically. He was the chief assistant district attorney in Cobb County during the trial and said every piece of evidence presented pointed to Harris' guilt.
"I have no doubt that Ross Harris murdered his son. Anyone who looks at the totality of the circumstance I think would reach that conclusion," Evans said.
He was shocked the Georgia Supreme Court overturned the malice murder conviction.
"We feel good about the evidence we presented at trial, we follow the evidence where it takes us, that's what we do in homicide investigations and prosecutions, and we felt confident, we thought we could put our best foot forward and we believe that we did," Evans added. "We believe that at the trial level we obtained justice for Cooper."
Evans said the sexually explicit messages Harris sent to minors were instrumental as evidence in proving why Harris murdered his son.
"The defendant was initially charged only with felony murder based on cruelty. It only became a malice murder case when we started digging a little deeper and finding out that his malicious intent was deeply embedded in some of his messages and some of his other behaviors," he explained.
But Harris' defense attorneys disagreed, saying the state crossed the line by showing the jury explicit pictures and videos.
"From day one we maintained that Ross was innocent," said Carlos Rodriguez, Harris' defense attorney. "The strategy of painting him as a philanderer, or someone who was unfaithful to his wife, has nothing to do with the love he had for Cooper."
In their opinion, the Supreme Court justices wrote that the prosecution spent too much time focusing on those text and could have tried to prove intent without them.
"I sincerely hope and pray that justice will be served again for Cooper and that my colleagues with the Cobb District Attorney's Office will continue the quest to get justice for Cooper," Evans said.
The district attorney's office has so far only said that it will ask the Georgia Supreme Court to reconsider its opinion. Legal experts said it's unlikely the court will do that.