If you committed traffic offenses within that 20 minute period, it is legal to be issued to tickets. Only way to dismiss them would be to prove that 1) It was not you driving, 2) That you did not commit said violations that you were ticketed for, 3) proving that the photo radar was not working appropriately at the time the photos were taken, asking for evidence with regarding the maintenance and operations of the radar unit.
These would require that you set for trial
The following website is a great source on fighting tickets
You can also find many "how to" books at your book store to prepare.
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