Cooper remained in Harris' car throughout the workday in June 2014, officials said. His father found him after leaving work and called 911. Charges against Harris include malice murder, two counts of felony murder and cruelty to children in the first degree.
Some of the charges in Harris' indictment stemmed not from Cooper's death, but from Harris' alleged habit of sending sexual text messages to underage girls. According to prosecutors, Harris was having these illicit chats with as many as six women on the day his son died.
In making her decision on the venue change, Judge Mary Staley said, "[Harris] has carried the burden to make a substantive showing of a likelihood that prejudice exists because of extensive publicity, so it would not be just to try the case in Cobb County."
Both the prosecution and defense had been working for weeks to find impartial jurors in the metro Atlanta county, interviewing potential jurors individually.
Given the change in venue, the jury selection will start again at a location and time that are yet to be decided.
Cobb District Attorney Vic Reynolds said his team was disappointed in the change of venue, but that, "whenever and wherever this case is set for trial, the state will be ready."
Both the prosecution and defense will now meet to see if they can agree on a venue within the state of Georgia. If they can't agree, the decision again falls to the judge.
Considerations for venue selection include the size of the trial, which will likely include dozens of investigators and other witnesses. Many of Georgia's smaller counties can't accommodate a trial of this size. Even if they can, the counties are not obligated to accept the trial, CNN Legal Analyst Philip Holloway said.
Moving a trial far from metro Atlanta will incur additional costs.
"The cost to the county will be very, very large -- in the hundreds of thousands of dollars to be sure," Holloway said.