Nancy Grace's reporting is always full of heated bias, vitriol, and vigor. Those who tune in to watch her are often swayed by what she says. It's hard to keep an open mind when you have a reporter like her spewing her own biases through the screen and into your living room.
Try as our courts might, it becomes nearly impossible to insulate a jury from the general details of a case. The 24 hour news media is constantly watching for stories anywhere that they happen. Nancy Grace is no different. As soon as she received information she was planning on when to release it to the public. The Jury then enters with a preconceived notion of guilt or innocence based on information they have seen.
The reporting of Nancy Grace did not affect the outcome of the Casey Anthony trial. That trial was based on evidence presented to the jurors and not on the opinionated reporting of Nancy Grace, although she did do a great job covering the case. The facts of the case were the determining factor in the verdict.
No Nancy Grace's reporting did not affect the verdict in the Caylee Anthony case, because Nancy Grace always implied that Casey Anthony was guilty. If Nancy Grace and her influence had had her way, Casey Anthony would have been convicted and hung behind the courthouse. Her influence had little effect on the jury.
Given that jurors are not allowed to watch news or media they would not have been influenced by Nancy Grace and if they were, they probably wouldn't have found Casey Anthony innocent. I do believe the prosecutors were influenced to seek the harshest offense, when it would have been more fitting to go after a lesser charge. Nancy Grace called out Casey Anthony as guilty, I assume she thinks her ethics and values and awareness of the case supersede the American justice system.