During a traffic stop, the police must have probable cause before they can arrest a driver for drunk driving. For example, a driver who admits to drinking may be arrested. However, it isn’t always that simple.

The police may need to test drivers to prove their sobriety. Here’s what you should know:

What are field sobriety tests?

The first thing the police may ask a driver to do to prove their sobriety is a field sobriety test. A field sobriety test is a physical examination. The police can ask drivers to perform certain actions that they may fail if they are inebriated. The National Highway Traffic Safety Administration has three standardized field sobriety tests:

  • Horizontal gaze nystagmus test
  • One-legged stand test
  • Walk-and-turn test

The police could ask the driver to do any of the three tests above or a non-standardized field sobriety test. Non-standardized tests can have the driver spelling the alphabet backward as they touch their toes. Proving a driver is drunk with these tests may not be successful if a driver has a disability, for example.

What are chemical sobriety tests? 

Alternatively, drivers may be asked to do chemical sobriety tests. Chemical sobriety tests evaluate the amount of alcohol in the body, which is called blood alcohol content (BAC). If their BAC is above the legal limit, then the driver may have broken the law. There are three kinds of chemical sobriety tests:

  • Blood tests
  • Breath tests
  • Urine tests

Out of the three tests, the blood test is typically the most accurate. However, many people take breath tests because the police can carry breathalyzers with them, unlike the other two tests.

A driving while impaired (DWI) charge can have lasting effects. Drivers may need to learn about their legal defense options when combating DWI charges.