The only way they can convict him of insider trading is to have a recorded conversation with his brother saying "our finances suck and we're going to miss"...and even that may be hard to do if they have scheduled investor calls (many companies do) where they hinted at missing or having difficulty meeting targets.
I don't doubt that a conviction is unlikely. But being convicted in court is not the same thing as being guilty, which is not the same thing as being morally wrong.
Also, keep in mind that Frist is not taking the "it was at a high point" defense, because that would violate his blind trust. His defense is that he got rid of the stock to avoid the appearance of a conflict of interest, despite having gone to some length over the years to keep the stock.
Jay