I don't know about you, but driving tired, and then saying that your tired is cause for an impared driving charge. This is as bad as if you were drinking ( not a .08, that's a separate charge ).
Bottom line is, a cop can make a mountain of trouble for you. Especially if the reason he pulled you over doesn't pan out. Most are pretty cool, but man, if you find an asshole with a chip on the shoulder....look out.