In Oklahoma and elsewhere, law enforcement personnel rely on three types of tests to measure blood alcohol content. In the interests of protecting your rights throughout the entire encounter with police officers during a traffic stop, it is a good idea to familiarize yourself with some of the basic details of blood alcohol testing.
The Breath Test: The portability of this method makes it the most commonly used test and the one with which most people are familiar. The test works by measuring any alcohol content present in people's systems when they blow their breath into the device. Several factors can have an effect on the accuracy of breath alcohol tests, but the results are still admissible as evidence in a drunk driving case.
The Blood Test: Less convenient, but more accurate, the blood test is law enforcement's second most used tool to determine if someone is driving under the influence. You can refuse to consent to a blood test, but in most cases that will lead to an automatic arrest. Although blood alcohol tests are typically the most accurate, lab errors and other factors could affect the results and cause a false positive or negative.
The Urine Test: Due to its high capacity to render false positives or negatives, urine tests are usually only given if other tests are unavailable for some reason. However, recently, a different kind of urine test has showed results that are more accurate. It is called an EtG or ethyl glucuronide test and it can reportedly detect the presence of alcohol in the urine much faster than ordinary urine tests, but it also has the capacity to deliver false positives.
The reason it is important to learn about testing methods is so that defendants can tell if a procedural or some other type of error occurs during the traffic stop or the alcohol testing. Even if no errors seem to occur, it is a great idea to consult with a DUI attorney as soon after the arrest as possible.
Source: BACtrack, "Three Types of BAC Testing," accessed May. 14, 2015