Most likely they will not. Photo radar is pretty limited in that there is no way to determine accurately if the person in the picture is the registered owner of the car. Most of the time it is, but where you have a valid alibi they will likely leave you alone and you'll never hear about this ticket again.
If you sign the waiver of service and mail it back, you validate the ticket. If you don't do that, some other service must occur.
"Summons and complaint may be served by first-class mail along with two copies of notice and acknowledgment of receipt of summons and complaint and postpaid return envelope, but service is not complete until the acknowledgment of receipt is executed." 16 A.R.S. Rules Civ.Proc., Rule 4.1(c), (c)(1, 2).
Essentially, that means the ticket -- which contains a court summons -- must be hand-delivered to you or a resident of your home if you do not validate it by mailing it back ( i.e. *service is not complete until the acknowledgment of reciept is executed.)
You need a lawyer. Check with an Arizona lawyer in your locale to discuss more of the details. I practice in Illinois.
Good luck to you.
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