Andy Wise comments on the trial of Roger Clemens, in which Brian McNamee, Clemens’ former trainer, is being described as a key yet problematic witness for the prosecution.  Even the defense will need to gauge how hard it goes after McNamee, Wise says.  "In some ways, it's a double-edged sword: The more you make McNamee look like a total scumbag, the more you chip away at your own client's image as the all-American idol," he continues.  "You can go after McNamee, but it had better be more along the lines of what his present-day motivation is rather than what a low-down, dirty scumbag he is, because your client was awfully close to that low-down, dirty scumbag," he says.