Kansas City Criminal Defense Lawyers
How Accurate are Field Sobriety Tests?

How Accurate are Field Sobriety Tests?

If law enforcement suspect that you are driving under the influence, they cannot simply arrest you on gut feeling, and they cannot force you to take a blood or breath test without your permission. These rights are protected by the Fourth Amendment which pertains to “unreasonable search and seizure.” Essentially what this means is that law enforcement must follow a very strict process in order to make any arrests and obtain evidence from someone they suspect of being guilty of DUI. The first step of this is to establish probable cause through the use of a field sobriety test.

Many people are aware of field sobriety tests. In fact, if you’ve been pulled over you’ve probably taken one before without realizing it. You also may have seen cops asking people to step out of the car and walk in a straight line or stand on one foot. While these tests may be proficient for determining suspicion of intoxication, many people also don’t realize how remarkably inaccurate they can be.

Three Types of Sobriety Tests

While the science behind intoxication was developing, law enforcement developed numerous field sobriety tests to try to accomplish their goal. In fact, tests would differ from precinct to precinct based on what was working and what officers believed did the job. However, this led to horrendous inaccuracy, and today the NHTSA has approved and standardized three different tests: horizontal gaze nystagmus, one-leg stand, and walk-and-turn.

  • The horizontal gaze nystagmus test involves the questioning officer holding up a finger, pen, or small light in front of you and then asks you to follow it with your eyes without moving your head. When intoxicated, your brain cannot control the muscles that move your eyes as precisely as it could while sober, so the officer will look for twitching or inability to follow the target to determine if the suspect is intoxicated. This test, when conducted properly, is the hardest to beat and also the most accurate, but even then is only on target just 77% of the time.
  • The one-leg stand test involves a suspect standing on one foot with their toes pointed out, looking up at the sky, and performing a mental task the officer asks, usually to count out thirty seconds. Sound difficult? It is. While stumbling isn’t the primary giveaway for intoxication, the inability to perform he mental test usually suggests an impaired mental state. However, if you think you would struggle to do this sober, you’re not alone. This is accurate just 65% of the time when conducted properly.
  • The walk-and-turn is slightly more accurate than the one-leg stand, but not by much. In this test, the officer has you walk heel-to-toe in a straight line for nine steps, while counting them out loud before turning on the spot without lifting your feet and then proceeding the other way. This sort of seems like a balance beam type-test, where the officer looks for your inability to process each of the different instructions you’ve been given. While this one may seem easier, it’s not a lot more accurate, at just 68% when conducted properly.

Because of this inherent inaccuracy, officers will often conduct a second field sobriety test if they find signs of intoxication in your first one. When all used together, the accuracy rating of these test rose to 82%. However, that’s still just under one out of every five people tested turning up a false-positive, leading to a potentially false arrest. Not to mention, this doesn’t include any errors in test administration that could easily happen when on the side of the road.

If you have been arrested for DUI, the Kansas City DUI attorneys at Rokusek Stein Law, LLC can help! We firmly believe that everyone deserves a high-quality and aggressive defense attorney when facing their criminal charges, and we fight to help you obtain the best possible outcome to your case. We review all of the evidence, including field sobriety tests you were administered to help determine whether your arrest was legitimate, and we work quickly to suppress any invalid or ineligible evidence that was obtained through a violation of your rights.

Before you face your DUI charges and hearings, call Rokusek Stein Law, LLC at (913) 583-0465 to schedule your free initial consultation.
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