field sobriety test, police officer holding pen for DUI suspect to follow with his eyes, HGN test, horizontal gaze nystagmus test

Are Field Sobriety Tests Accurate?

Problems with Field Sobriety Tests

To determine if a driver is impaired or intoxicated, police officers typically require these DWI suspects to take the Standardized Field Sobriety Test (SFST). The SFST is a battery of 3 tests designed to measure certain functions and capabilities that become impaired by alcohol and drugs.

If you watch cop shows on TV, you’ve likely seen DWI suspects walking in a straight line, balancing on one leg, and following a penlight with their eyes. These are all part of the SFST, which we discuss in detail below.

However, field sobriety tests have serious problems and cannot be trusted as a result. Suspects may end up in handcuffs because their field sobriety test results misled officers into thinking a DWI has taken place.

Types of Field Sobriety Tests

The Standardized Field Sobriety Test consists of the following three tests:

  • Horizontal gaze nystagmus (HGN) test: This test measures the involuntary jerking of the eyes as they move side-to-side. When a person is intoxicated, their nystagmus may occur at lower angles, preventing them from smoothly tracking a moving object as a result. As such, an officer will tell a DWI suspect to follow a pen or penlight as it moves side-to-side, allowing the officer to examine if the suspect’s nystagmus is exaggerated.
  • Walk-and-turn test (WAT): A police officer will instruct the driver to take 9 steps along a straight line, walking heel-to-toe, with their arms relaxed at their sides. After completing 9 heel-to-toe steps in one direction, the suspect will do the same thing but in the opposite direction.
  • One-leg stand test (OLS): To conduct this test, a police officer instructs the suspect to raise one leg 6 inches from the ground with both arms relaxed to the side for about 30 seconds. At the same time, the suspect may be asked to count in thousands (one thousand one, one thousand two, etc.).

How Accurate Are Field Sobriety Tests?

According to an analysis by the National Highway Traffic Safety Administration, HGN tests are 77% accurate, WAT 68%, and OLS 65%. Believe it or not, police officers continue to administer these tests in DUI stops despite their low level of accuracy.

Keep in mind that SFSTs are conducted at the locations where drivers are pulled over. These locations often include parking lots, highway shoulders, and streets. As such, external factors could strongly impact field sobriety test results. In addition to external factors, underlying factors such as medical conditions could lower the reliability of SFSTs, which you can see below:

HGN: An officer may not have moved their penlight smoothly from side to side, causing the suspect’s nystagmus to become exaggerated. Other factors such as bright headlights from the surrounding traffic, fast-moving objects, or underlying medical conditions such as central nervous system disorders may create a false indication of intoxication.

Walk-and-turn: Walking heel-to-toe is not easy on an uneven or slippery surface. Not to mention, certain shoes such as heels and sandals make it challenging to walk, let alone in a straight line heel-to-toe. Weather conditions such as rain, snow, and wind could impede a suspect’s ability to successfully complete this test, in addition to physical disabilities.

One-leg stand: As mentioned above, if you were wearing improper footwear, had a physical disability, or took the test in poor weather conditions, your walk-and-turn test results could be skewed. One-leg stand tests are no exception. These factors could easily impede a suspect’s ability to balance on one leg for 30 seconds while counting aloud. Imagine taking the one-leg stand test in the rain or while wearing heels ― it would be very challenging.

Are Field Sobriety Tests Admissible In Court?

Field sobriety tests are generally admissible in Texas courts. However, a good lawyer can argue that such evidence should be inadmissible in court due to its unreliability. Underlying medical conditions, weather conditions, external conditions, and other factors could produce false field sobriety test results. Depending on the circumstances that lead to your DWI arrest, our attorneys can work to identify any flaws or inconsistencies with your results and use them to your advantage.

Our mission is to help get your DWI charges reduced or dropped altogether. To learn how we can help achieve this goal, give us a call at (979) 559-3599!