I practice in Florida, and we've seen alot of successful challenges to photo radar units, both pertaining to speeding tickets and toll pass violations. You should consult a local attorney immediately regarding your rights in fighting this ticket. The legal problems down here involve the due process violations that stem from assuming that the person that committed the infraction is in fact the person in the photo, when they don't match up (as is your case), it's not fair to punish the registered owner of the vehicle, nor is it fair to put any pressure on them to identify the driver (isn't that law enforcement's job, to find the bad guys?).
You should consult with a local attorney immediately,
I am an Arizona licensed attorney.
Are you sure it was a "CRIMINAL" speeding ticket, as opposed to a CIVIL speeding ticket? The Maricopa County Attorney has essentially declared that his Office will NOT be prosecuting CRIMINAL speeding tickets that arise from photo radar (because of service of process and federal/state constitutional Confrontation Clause issues). Generally, criminal speeding tickets are issued for travelling 21 miles over the posted speed limit, or over 85 on a highway.
Assuming that it is a CIVIL traffic ticket, my advice would be to mail in a copy of YOUR drivers license with a written statement that you are NOT the driver in the ticket. That's it. You are under no obligation to "rat" out your friend. The State retains the burden of proving that YOU were the driver.
Radar data does sometimes give rise to defenses that can be raised as does photo evidence. You need to be represented by an attorney skilled in these matters, though, to best take advantage of any potential defenses.
Good luck to you.
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