Your question does not provide the state in which you were stopped or the type of speed detection device that allegedly measured your speed. Depending on the state in whch you were stopped and the type of speed detection device (ie: LIDAR (Laser), Radar, Vascar, Stopwatch, Pacing) the answer to your question would be different. For example, in the State of Georgia, a speed detection device (Radar, or Laser) must be checked for accuracy when the device is put in service at the beginning of the officer's shift, and at the end of the shift when the officer goes out of service. With RADAR, this is done with two tuning forks of different frequencies and by doign a light segment test to make sure all light segments on the display are operational. With LIDAR/LASER, the officer performs a check of the device by obtaining a measurement of distance onthe device at a measured distance. In addition to this there is a statutory requirement of a yearly calibration of the deivce.
You may be able to fight the ticket. The state would have to prove that the device used to measure your speed was appropirately calibrated in order for the judge to rely on that technology to convict you. However, some judges will allow an officer to testify to a visual estimate of speed and use this as the basis of a conviction. If you are going to fight, you should hire a lawyer to assist you.