Once you have been placed under arrest for suspicion of DUI, the laws in each state require you to submit to a formal chemical test of your breath, blood or urine. Some jurisdictions allow the suspect to choose which test they take, while others may not.
The Breath Test
The most common and least invasive test is performed on a Breathalyzer machine, and these are manufactured under a variety of brand names, such as Intoxilyzer. Each device uses a different type of method to estimate the alcohol concentration level. A criminal defense attorney may question the results of these tests because some machines are prone to interference and contamination from other substances. Before the police officer administers the breath test, they must observe the suspect for a period of time (usually 15 to 20 minutes) and watch for signs of burping or vomiting.
The Blood Test
Blood and urine tests are generally administered if you are suspected of driving under the influence of drugs or a combination of both drugs and alcohol. Depending upon where you were arrested, the officer may tell you which test you will be given rather than giving you a choice. However, if you have a serious medical condition, such as hemophilia where your blood does not clot properly, you will be exempt from the blood test and asked to provide a urine sample. Each state has guidelines regarding how and by whom a blood test will be administered. Most laboratories and hospitals must be certified or approved by the state to administer a blood test. In addition, there are laws dictating the approved method of testing and the time limit in which the blood must be drawn.
The Urine Test
A urine sample is considered the least reliable of the chemical tests. In certain states they are only used to detect the presence of drugs. However, urine tests cannot substantially prove when a drug was actually was used. The test can only detect leftover traces of substances that were previously ingested. For example, the active ingredient in marijuana is called THC, which is stored in the fatty tissues of the body. Urine tests can detect the presence of this drug for up to two weeks.