I think this all boils down to what the jury will believe.
I also think that it would be stupid for the defense to dispute the smell in the car, but that is just my opinion.
From a juror's point of view, they have to choose which expert is stating forensics from a factual standpoint correct? One of them will say one thing, and the other will say human decomp..
This in my opinion is where any juror who has no forensics background, nor has ever smelled a dead body, must use their common sense. How else could they determine the smell in the car?
With only one expert and Casey's statement about Zenaida taking Caylee, compared to the cadaver dogs, LE, Cindy, George, Lee, Yuri, and the umpteen dozen other people who smelled the "smell", why would the defense even begin to argue the smell?
It seems to me that the longer they dispute the smell in the car, the worse the jurors feel about Casey's guilt..
JMHO