Are Field Sobriety Tests Accurate?

Standardized Field Sobriety Test Flaws

Drivers may get a DWI charge without being impaired or intoxicated. You may have had moments on the road where you accidentally swerve out of your lane, don’t fully stop at a stop sign and drive slower than usual. These actions may not be concerning to you, but to a police officer, they can signal impairment.

When a police officer has reasonable suspicion to pull you over, they may ask questions such as, “Where are you coming from?” “Do you know why I pulled you over?” “How much have you had to drink?” Following these questions, they may ask you to step out of your vehicle to take a Standardized Field Sobriety Test (SFST).

Types of SFSTs

The SFST is a battery of three tests used to evaluate signs of intoxication and establish probable cause to arrest you for driving while intoxicated (DWI). These tests are designed to test your normal use of mental and physical faculties, but they are severely flawed. The three SFSTs include:

  • horizontal gaze nystagmus (HGN) test: Horizontal gaze nystagmus is an involuntary jerking of the eyeball when it gazes to the side. When a person is intoxicated, their nystagmus becomes exaggerated and may occur at lower angles, and they may have trouble tracking a moving object smoothly. Typically, an officer will use a pen or penlight as the object and require the suspect to follow the object as it moves from side-to-side.
  • walk-and-turn test: An officer will ask you to stand heel-to-toe with your arms relaxed at your side. They will instruct you to take nine heel-to-toe steps along a straight line, and turn on one foot and conduct the same nine heel-to-toe steps in the opposite direction.
  • one-leg stand test: This test is often tricky for people. This test requires you to stand on one leg and raise your other leg six inches off the ground with both arms to the side. Simultaneously, you will count in thousands (one thousand one, one thousand two, etc.) for about 30 seconds or until the officer asks you to stop.

SFST Flaws

As mentioned earlier, SFSTs are intended to examine your normal faculties to determine if you are intoxicated or impaired by alcohol and drugs. However, it’s important to remember that these three tests measure things that we do not normally do.

People do not walk heel-to-toe, nor balance on one leg, in their daily lives. Others may have optokinetic nystagmus and other underlying conditions can result in a false result on their HGN tests. Let’s take a closer look at the SFST flaws and inaccuracies that can result in your DWI accusation.

HGN test: 77% accurate

  • Use of prescription medications such as asthma inhalants
  • Nervous system diseases
  • Vestibular system diseases
  • Stroke disorders
  • Neurodegenerative disorders
  • Metabolic disorders

Walk-and-turn test: 68% accurate

  • Improper footwear
  • Bad weather conditions
  • Vertigo, balance issues and health conditions
  • Slippery or uneven surfaces
  • Distractions of speeding cars passing by

One-leg stand test: 65% accurate

  • Poor weather conditions
  • Vertigo, balance issues and health conditions
  • Inappropriate footwear
  • Unfair surface conditions
  • Interference of speeding cars nearby

All of these tests have one flaw in common: Test instructions. Police officers have a crucial responsibility to administer SFST instructions correctly, and if they don’t, you may pay the price. Any incorrect, unthorough and unclear directions on behalf of the cops could do some heavy damage that may result in jail time, fines and license suspension.

Don’t let this happen to you. Retain a proven San Antonio DWI defense lawyer to handle your case and evaluate it for defects and inconsistencies. We obtain knowledge on both sides of the law and 70+ years of combined legal experience, therefore we have what to takes to help you put your DWI charges behind you.

Schedule your free consultation by contacting (210) 801-9400. Hablamos español.

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