A missing calibration log can significantly weaken the prosecution’s reliance on a breathalyzer reading because it raises questions about whether the device was functioning properly at the time of testing. If no documentation shows that the device was checked, maintained, and calibrated according to required schedules, a court may view the reading as less reliable. This does not automatically invalidate the result, but it creates a substantial factual issue that defenses can use to undermine the test’s weight in a Collins DUI case. Challenging a reading on that basis typically requires formal requests for records and a clear presentation showing the absence or inconsistency of calibration documentation. The defense may argue that without consistent calibration evidence, reasonable doubt exists regarding the accuracy of the device’s measurement. In Covington County, courts weigh such issues in suppression hearings where the presence or absence of calibration logs and maintenance records is often pivotal.