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Tests Used to Determine if You are Under the Influence of Drugs or Alcohol

Posted by Coleen D. St. Clair | Oct 21, 2016 | 0 Comments

If you are suspected of driving under the influence of drugs or alcohol and you fail or refuse a field sobriety test, you may have to undergo more invasive chemical testing. There are a number of different chemical tests that can be administered if you are suspected of driving under the influence: breath, saliva, urine, and blood. The results of these tests may determine whether you are charged or convicted of a DUI.

Breath Test

The most commonly used test for a DUI is the breath test. Breath tests are only administered to determine blood alcohol content, but they can be conducted roadside, at a hospital, or at a police station. This test measures the alcohol content of exhaled vapor and a computer translates the data into a BAC measurement. Breath tests are the least invasive method of testing, but they are less accurate.

Saliva Test

A saliva test may be conducted if you are suspected of being under the influence of drugs. The test is administered by taking a small amount of saliva from your mouth and testing it for the presence of a number of different drugs. The common drugs that are tested for in a saliva sample are THC (marijuana), opiates, cocaine, amphetamines, methamphetamine, ecstasy, and PCP. The saliva test can reveal whether or not a person has smoked or ingested an illegal substance within a 72 hour period. The test is much simpler, quicker, and much less invasive than the traditional blood and urine tests.

Urine Test

A urine test can be used to test for the presence of both alcohol and drugs, such as amphetamines, marijuana, cocaine, and opioids. The urine test is not as commonly used because it is the least accurate of the chemical tests. The test can fail to capture same-day drug use and it can create a false negative even if there has been drug use.

Blood Test

The most accurate test of drugs or alcohol in the body is the blood sample test, but it is also the most invasive. The blood test measures the amount of drugs or alcohol in the blood at the time the sample is taken. Blood tests may be requested by an officer if a person refuses to submit to other chemical tests, usually after a serious accident. In any case of DUI, if a person refuses a breath test, the officer may seek a warrant to obtain a blood test.

Implied Consent

Washington law requires you to take a breath or blood test if you are arrested for a DUI. If you refuse to take the test you will lose your license for one year and the evidence of your refusal can be used against you in court.

Washington DUI Attorney

Regardless of the circumstances, anyone facing charges of driving under the influence has the right to a quality legal defense. An experienced attorney will know how to question the accuracy of chemical testing. If you have been arrested in Washington State, suspected of DUI, call Coleen St. Clair at St. Clair Law Offices (206) 578-2200 or contact her online.

About the Author

Coleen D. St. Clair

Ms. St. Clair is a former senior prosecuting attorney with over 25 years experience handling criminal cases. She has successfully handled tens of thousands of criminal and DUI cases with remarkable results.


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You must be confident in the experience and ability of your attorney. Effective representation requires trust, confidence, communication and a shared goal. Your future depends on it. If you have been charged with DUI or a criminal offense in King County, Snohomish County or Pierce County, we can help. Call Seattle criminal defense firm St. Clair Law Offices today to discuss your case. 206-578-2200. Your initial consultation is free.