This is a very good question. There are two kinds of chemical tests under California state law to determine a driver’s blood alcohol content (BAC) at the time he was stopped on suspicion of driving under the influence of alcohol, drugs, or both. Until recently, there was also a urine test which was part of the drivers choice of tests. This test after many years. was eliminated by the legislature due to their determination that this type of test did not meet the high standards of accuracy required by the law.
There are two remaining tests which a suspected drunk driver has to chose from. These tests are the blood and breath tests. The blood test, which most experts view as the more accurate of the two because this test essentially through a direct analysis, measures the percentage of alcohol in the blood drawn from a suspected driver.The result is a blood alcohol concentration or bac which is directly correlated to the language of the law prohibiting blood-alcohol levels of .08 or over.
In addition, if the suspected driver is also under the influence of a drug, a blood test or urine test is the only way to determine their presence. A breath test is only capable of measuring alcohol.
The breath test, has been determined by the federal government under title 17 to be sufficiently accurate for blood-alcohol testing of suspected DUI drivers. Current models of these sophisticated machines have a very high accuracy rating, although require regular and frequent maintenance and calibration to be reliable. It has been determined that these machines have .02 allowable error range.These machines use heated gases and other very sophisticated techniques to convert one’s breath into a blood-alcohol reading to be measured against the requirements of the law. These breath testing machines are subject to a variety of possible errors that make it more susceptible to generating inaccurate and erroneous results. There are two common types of errors. Operator errors occur when the officer fails to follow the specific steps prior to using the machine.
One example is that title 17 requirement that the driver be observed continuously for at least 15 minutes before the test is given. The purpose of this requirement is to prevent the machine from reading possible mouth alcohol present either from recent drinking or coughing, belching or regurgitating prior to the test which could overstate blood-alcohol present.This second type of error is also very common.
Our firm of DUI specialists, carefully inspect for each DUI case we defend the maintenance and accuracy logs before and after our clients has blown in to this machine. These errors can get cases dismissed or reduced in Court.