Pretty much a 'given' that they had to get this loony medicated enough to plead out.  If they had gone to trial the defense would have certinaly called Giffords to the stand - the world would have seen what her mental state is really like and the defense's examination on the witness stand would have absolutely destroyed her.   

This is the best for all involved.  Giffords is protected, the parents of the little girl don't have to relive her death, and Justice may visit this loser in a prison laundry room one day.

http://www.azcentral.com/news/articles/2012/08/08/20120808tucson-shooting-loughner-victims-closure.html