The legal limit for blood alcohol concentration while operating a vehicle in California and other states is .08 percent for those over 21, and motorists above this limit could face charges for driving under the influence. Law enforcement agencies attempt to find out BAC by conducting blood or breath tests. Blood testing is more accurate, but Breathalyzers and other breath testing equipment allow the police to measure BAC in the field.
Breath analysis testing devices measure one's BAC level when they blow into the device, and the findings from breath tests can be used in court but are not considered scientifically accurate. Breath tests are not always correct, so the prosecution must show that the machine used is reliable. If a device was not in working order when a test was conducted, one could challenge the results.
Maintenance and calibration are required to ensure that breath tests produce accurate results, but there is not a single time frame for how often testing equipment needs calibration. For admissibility in court, a breath device generally must capture two readings within .02 percent of each other, be regularly checked and be on a state's list of acceptable devices.
The person administering the breath test must also use the device correctly and must be certified. They must also ensure that the test taker does not smoke, eat, burp or vomit right before testing.
A DUI conviction may result in a license suspension, fines, jail time and a permanent criminal record, so one might wish to obtain legal counsel and fight any charges. Aside from questioning the results of a breath test, one could also question the events leading up to any tests, such as whether the officer had a reason for pulling the vehicle over.