When a person is stopped on suspicion of driving under the influence, they are asked to take a preliminary alcohol screening test (PAS) at the scene. The PAS is optional, but the test administered at the police station is mandatory. In both situations, the person will be offered the choice of taking the breath or blood test in order to get a reading of their Blood Alcohol Content (BAC).

A breath test is not the most accurate alcohol screening test because after it obtains a sample, it must be converted to a BAC. It is not as direct as a blood test, which has a higher probability for accuracy.

Can there be errors in a BAC reading from a breath test?

Several external factors can affect a Breath Test reading. Temperature can affect the reading. It must be adjusted to accommodate the surrounding temperature, and the temperature of the subject. Breathing patterns may also have an effect on the reading of the breath test. Hyperventilation and excessive exercise will cause the reading to be inaccurate.

Furthermore, the breathalyzer machine must be calibrated frequently. Breathalyzer machines also have a problem of non specificity. They don’t specifically pick up only alcohol on someone’s breath, they pick up similar substances with a comparable molecular structure like acetone.

A California DUI Attorney can request the records for a specific breathalyzer machine to test it for accuracy and proper maintenance.

Are there any legal defenses for refusing to take a breathalyzer test?

A person may refuse to take a breathalyzer test in certain situations. If they have asthma, they are legally excused from taking the test. They may also be excused if the machine is giving erroneous or inaccurate readings. However, it is important to note that a person may legally be excused from taking a breathalyzer test, but they may still be required to take a blood test.