If you are stopped on suspicion of drunk driving, there are several different types of DUI tests that state DUI laws allow as evidence. Here’s an overview of the testing for DUI that happens in most communities. If you’re not familiar with any of the terms used, see a detailed DUI glossary for definitions.

In this Drunk Drivers Rights article, we will help you understand what types of tests you can expect if you are under suspicion of drunk driving.

Breathalyzer Tests

While there are different brand names for the machines used, the most common is the Breathalyzer. It measures blood alcohol concentration, or BAC, in terms of a percentage. Mobile breathalyzer machines are often carried in police vehicles and larger, more accurate machines are often found at the police station.

If you are charged with a DUI based on a breath test, your DUI attorneys will scrutinize the test very carefully. This is because there are quite a few things that can go wrong with the test, indicating BAC levels higher than they actually are.

Field Sobriety Tests

In some states, law enforcement can arrest you for driving while impaired even if your BAC is not above the legal limit. If you are driving erratically and are pulled over, you might be given field sobriety tests, also formally called Standard FSTs by the NHTSB.

There are many tests that are used. These include mental tests such as counting backwards from 100 or reciting the alphabet. Contrary to urban legend, you will not be asked to recite the alphabet backwards, a task that can be difficult when sober.

Physical field sobriety tests might start with the Horizontal Gaze Nystagmus in which you are asked to track an object with your eyes as it is moved in front of you. The eyes of a person who is impaired will jerk as they follow the object rather than track it smoothly.

The Rhomberg Test is the test in which a person is asked to close their eyes, tilt their head back, and touch the tip of their nose with an index finger. Coordination and balance are tested.

Additional FSTs include the heel to toe walk and standing on one leg.

Urine Test

Blood alcohol can also be determined by a urine test, though this is proven to be the least accurate. Your DUI attorneys will certainly question the results of a urine test, especially if it is the primary evidence presented against you.

Blood Test

The most accurate way to determine blood alcohol concentration is through a blood test. The DUI laws in some states require a blood test for conviction. DUI attorneys can raise a defense even against a blood test. It is called the rising curve or rising BAC defense. Again, see a good DUI glossary for an explanation of this defense.

This is an overview of the different types of DUI testing used in most states. Laws about which tests are given vary by state. Good DUI attorneys will examine the procedures surrounding the tests and seek to have them thrown out as evidence if they were not administered correctly or if their results can be reasonably disputed.