Terrorists aren't stupid and they can play games, too.
Look. Just as (in my opinion) the anthrax killer is a DOMESTIC KOOK who purposely wrote those letters to Capitol Hill, the White House, the Supreme Court, with strange grammar and "Allah Ahkbar" to make it look like a foreigner did it, there is just as much an equal, reverse possibility that a savvy Islamist terrorist (who has been here for years or may even be an American) could set the stage for the planting of evidence to 'make it look like a DOMESTIC KOOK case.
I see these two cases, ANTHRAX and now MARYLAND SNIPER still as reverse of what they appear on the surface to be.