I read the defense's motion for the change of venue. They said that there were 85 jurors who were questioned about the case, and of those 85, they determined that 43 could not be impartial. That's about half. So I don't think finding an impartial jury in Cobb would've been impossible but I don't have a problem with them moving the trial. I would even argue that w/ all the hype and attention this case has gotten, the fact that half of the jurors in the same county can be impartial (and you know the defense is trying to get as much numbers of their side as possible), is relatively surprising.
https://www.scribd.com/doc/311224797/Harris-Motion-Doc-1
The State's argument against COV rested upon numbers. The DT argued that the Irwin US Supreme Court ruling had mandated a different standard in cases where pervasive pre-trial publicity could be demonstrated. The standard in such cases was that prospective jurors' claims of impartiality could not be trusted, in essence, and that juror bias must be presumed.
Staley's statements when ruling in favor of the COV indicate she accepted the Irwin standard. She specifically pointed out that at least some jurors who said in questionnaires they could be impartial reversed themselves when testifying, and likewise, at least some jurors who they couldn't be impartial also reversed themselves in testimony. Bias must be assumed.