The Arizona code section for parking in a handicapped space is ARS section 28-884. As far as it applies to your situation, it reads:
28-884. Parking space for physically disabled persons; prohibition
A. Except as provided in subsection B, a person shall not stop, stand or park a motor vehicle within any specially designated and marked parking space provided pursuant to this article unless the motor vehicle is transporting a person who has been issued a valid placard or international symbol of access special plates and either:
1. The motor vehicle displays the valid permanently disabled or temporarily disabled removable windshield placard.
2. The motor vehicle displays international symbol of access special plates that are currently registered to the vehicle.
(Subsection B relates to temporary stops to unload handicapped persons from vehicles not displaying the required placard or plates.)
The code section is clear and unequivocal. It requires that you either have the special plates or have the windshield placard in place. The fact that you may be entitled to use the space is not a defense to parking in it without having the windshield placard on display.
I could find only one reported appellate court case on the subject of handicapped parking, which is not surprising since parking tickets rarely end up in the court of appeals. It is a Maricopa County Superior Court case; however, it addresses a different issue than the one you raised so won't help you. If you want to, you can see it at:
The statute you were charged with violating requires that the tag be in the windshield. Since it was on the floor, you were in violation of the section. The judge could have given you a break, but apparently chose not to.
Unfortunately, the appeal court does not have the same discretion. On appeal, the court can consider only whether the trial
court made an error of law in arriving at the conviction. In my opinion, an appeal of this conviction has no chance of succeeding.