These are two different things. The insanity defense is just that... a defense against a crime. This strategy says that yes, you did it, but at the time you were mentally ill. By the way, this defense very rarely works.  This concept is used at trial. On the other hand, guilty but mentally ill, is not a defense but rather an adjudication. In other words, the latter is how the court ruled. The former is used by your lawyer in your defense. You might want to consider trying to get your record expunged(wiped clean). Contact your lawyer to do this. Basically, your lawyer writes a letter, that's it. It may or may not work. If you could do this however, you might be able to get the Hazmat endorsement.