I hear what you are saying , however the law is very precise as to the correct procedure and the manner in which the officer records, reports and conducts the offense. In this case the officer has failed to inform you of your rights and has failed to follow the correct course of actions. You are not denying the offense as technically you have no offense to answer, on the grounds that the set procedure had not been adhered to. Almost as B3ar points out. You could have the charge quashed if you questioned the conducting officers procedure together with request of copy of the calibration certificate.
Where has the officer failed to inform you of your rights, he told Shiralee she could contest it
The office should have informed Shiralee as to the correct manner in which to dispute the alleged offense, and in just saying you can contest it, he failed to explain the differing courses of action in the set procedure. There by the officer failed to inform her of her rights.