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DUI Chemical Tests

Under California law, chemical tests are used as part of a driving under the influence (DUI) investigation to measure the amount of alcohol or drugs in a person's body at the time of arrest. DUI chemical tests can take samples of the driver's breath, blood, and/or urine. The results of these chemical tests will be used as evidence to show an individual was driving under the influence.

In most drunk-driving cases, a chemical test is used to show the driver's blood alcohol concentration (BAC). A BAC of 0.08% or greater can be used to show a driver is per se above the legal limit to operate a vehicle. For commercial drivers, the limit is 0.04% percent and for drivers under the age of 21, the limit is 0.01%. Chemical tests are also used to detect evidence of drugs in a driver's system.

Chemical Testing in California DUI Cases

Chemical testing in California DUI cases can be confusing because some tests are not required, while there are consequences for refusing other tests. The difference involves whether the test is done as part of a roadside stop or after the individual was arrested on suspicion of a DUI. Topics involving California DUI chemical testing include the following.

  • Roadside Breathalyzer or “PAS” Test
  • Chemical Test Refusal
  • Types of DUI Chemical Tests
  • Problems with Chemical Testing in DUI Cases

Preliminary Alcohol Screening Tests

A roadside breath test is not required. When the police conduct a stop on the side of the road and ask a driver to blow a breath into a handheld breathalyzer, this is part of the field testing and drivers are not required to submit these breath tests. This is known as a Preliminary Alcohol Screening (PAS) breath test.

California's implied consent laws for chemical testing apply after a lawful arrest. You do not have to submit to a field PAS test. The officer may suggest they will arrest you if you don't submit a test or try and convince you that it is in your best interest to submit to a test. However, these tests are not mandatory and you can refuse. These tests are used as an investigative tool to give an officer reasonable suspicion to arrest a driver for DUI. However, if you are under 21 or on probation for a DUI, you must submit to a PAS test.

Chemical Test Refusal and Required Chemical Testing

Under California's implied consent laws (California Vehicle Code VC Section 23612), if a person driving a vehicle is arrested for driving under the influence of alcohol or drugs then the person is the police are supposed to advise you that you will need to take a chemical test to determine the alcoholic content of your blood. This test can be either breath or blood. You should be advised that you have the choice of breath or blood.

If you refuse a chemical test after arrest, your license can be suspended. The penalties for refusing a chemical test depend on your prior record. A first-time refusal may result in a one-year suspension of your California driver's license. Refusing a chemical test after a prior DUI conviction can result in a suspended license for two or more years.

Types of Chemical Tests

There are three types of chemical tests generally used in DUI arrests in California. The test may depend on the driver and the law enforcement officer. Generally, a driver arrested on suspicion of drunk driving can have a breath or blood test. However, if the officer reasonably suspects that the person is under the influence of drugs, or a combination of drugs and alcohol, then the officer can require a blood test. If you have been taken to a hospital, breath testing may not be available and blood may be the only choice. If neither test is available, the driver may have to submit to a urine test. However, urine testing is very limited.

Breath Testing

A breath test machine is different from the portable PAS tests. These tests generally take place at the police station or jail. Breath tests are more common because they are easier and faster to administer. Breath test machines can be operated by non-medically trained personnel; however, to be considered “reliable,” they have to be properly operated, checked for accuracy, calibrated, and maintained.

Blood Testing

Blood tests can either be administered at the police station or in a hospital setting. Blood tests are sometimes considered more reliable measures of BAC than breath tests. Blood tests also test for the presence of drugs or other substances while breath tests only detect alcohol.

Urine Testing

Urine tests are less common and not often employed. However, they are used when other tests are not available, or the driver cannot submit to a blood test for medical reasons. Urine tests can be used to measure the levels of alcohol or drugs in the suspect's body.

Problems with Chemical Testing

There are a number of problems with the use of chemical testing in DUI cases. These test results are not always a good indicator of the driver's impairment at the time they were driving. There are also a lot of false-positives that can show up as “drugs” or higher alcohol levels on a chemical test.

Chemical testing also has to be performed accurately to be reliable. This includes having the tests conducted appropriately, the use of properly maintained and calibrated equipment, properly trained staff, employing accurate observation times, using acceptable medical practices and taking measures to prevent contamination or misidentification. When there are problems with the way breath and blood tests were conducted, an experienced DUI defense lawyer can challenge that evidence in court or have the evidence suppressed so it cannot be used against the driver.

East Bay DUI Attorney Defense

Chemical tests in a DUI case are used as evidence of impairment but can be unreliable. If you submitted to a preliminary breath test or chemical test, or you refused a chemical test, an experienced East Bay DUI defense attorney can fight for you. With over 30 years of DUI experience, Lynn Gorelick understands the law and the science required to fight drunk driving, and drug DUI charges.

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