Without any proof that information was shared, the decision he made to ask the trustee to sell (which, by the way, it took over 3 weeks to actually implement) can easily be explained as the man making a decent investment decision, all by himself.
If anybody is going to know what a good value for the stock is at any point in time, it is going to be Frist and other family members involved in the business. His brother, by SEC rule, cannot trade the stock 30 days before or after a financial reporting date because he is actively working within the org.
The Sen actually gave notice to sell on the day before that requirement...actually meeting the rules of the SEC for an insider.
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.