Just to follow up on something: I've always assumed that Geary wasn't actually part of the committee, because he excuses himself to go elsewhere and I can't imagine a member of such a high profile committee doing that. I don't think that it would be an exceptional circumstance for a senator to sit in on a committee hearing without being a member of the committee, provided that he had some interest in the subject matter.
Actually, since there are usually about 20 Senate standing committees and only 100 Senators, each Senator is a member of several committees and most Senators are the Chair or vice-chair of at least one committee or sub-committee. Given constraints on a Senator's time, it's unlikely that a Senator would sit in on the proceedings of a committee of which he was not a member.
