Problems with Field Sobriety Testing: Are They Reliable?

Why You Can’t Trust OWI/DWI Field Sobriety Tests

A casual drive home can quickly turn into an OWI arrest if you “fail” the Standardized Field Sobriety Test (SFST). The SFST is a battery of three tests used to determine whether there is probable cause to arrest someone for operating while intoxicated (OWI), and while they have been widely used for decades, they can be inaccurate and unreliable for various reasons.

Before we discuss those reasons, let’s examine the three types of field sobriety tests below:

  • Horizontal gaze nystagmus (HGN) test: This test measures the involuntary jerking of the eyes, which occurs when they move side-to-side. However, when a person is intoxicated, their nystagmus may occur at lower angles and they may be unable to smoothly track a moving object as a result. HGN tests require a person 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: An OWI suspect will be asked to take nine steps along a straight line, walking heel-to-toe, with their arms relaxed at their sides. An officer will then instruct them to turn and take nine heel-to-toe steps back in the opposite direction.
  • One-leg stand test: A police officer will instruct 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.). If you’re thinking this field sobriety test is challenging for many people, you’re right.

Although field sobriety tests are a standard component of OWI stops, that does not mean they are 100% accurate. SFSTs measure your normal functions to determine whether you are impaired or intoxicated, but after learning how these tests work, it’s fair to argue that normal functions to do consist of walking heel-to-toe and balancing on one leg, for instance. As such, one minor slipup can have costly outcomes.

The effectiveness and accuracy of SFSTs depend on various factors, such as the officer’s test instructions, weather conditions, and the suspect’s underlying medical conditions. You should also know the National Highway Traffic Safety Administration reports HGN tests being 77% accurate, walk-and-turn tests 68%, and one-leg stand tests 65%.

We encourage you to take a closer look at the following factors that may impact the reliability of field sobriety tests:

HGN test

  • Prescription medications
  • Nervous system disorders
  • Vestibular system disorders
  • Metabolic disorders
  • Fatigue
  • Stress

Walk-and-turn test

  • Improper footwear
  • Poor weather conditions
  • Balance issues and health conditions
  • Road conditions such as slippery or uneven surfaces
  • Distractions of headlights and noise from passing cars

One-leg stand test

  • Poor weather conditions
  • Balance problems and health conditions
  • Unsuitable footwear
  • Uneven and slippery road conditions
  • Interference of passing cars

Arrested for OWI in Des Moines?

An OWI conviction can strip you of your driving privileges, livelihood, and reputation. Not only will your license get suspended but you may also suffer jail time, fines, and more. Don’t let this happen to you. To increase your chances of getting reduced or dismissed charges, retain our Des Moines OWI attorneys at Branstad & Olson Law Office to defend your case. Backed by 65+ years of combined experience, we know what it takes to help you come out on top.

Schedule a free consultation to discuss your situation and learn about your legal options today. To get started, please contact us at (515) 329-3100!