I don't know what he would say, and neither do you. This will never get to trial, so it won't matter anyway.
What it boils down to is this: you have an officer with a clean record versus a thug with weed in his system who just committed a robbery. The star eyewitness also happens to have been with Brown during the robbery, and claims Brown was "shot in the back", which he wasn't. The autopsy report is, at best, inconclusive.
No prosecutor in the world would touch a case like that, no jury would convict him, and if Wilson was injured by Brown, the chances of him being tried drop from about 2% to 0%.