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Are Field Sobriety Tests Reliable?

Why Standardized Field Sobriety Test Can’t Be Trusted

Drivers who get pulled over on suspicion of driving under the influence (DUI) are often told to take a Standardized Field Sobriety Test (SFST), a battery of three tests that are administered to determine whether a person is intoxicated. Each test measures a different function, and if a driver insufficiently or poorly demonstrates the specified function, a police officer will likely assume that they are intoxicated and arrest them as a result.

This could be a costly mistake, as countless drivers get DUI charges despite being 100% sober. Why?

SFSTs test several abilities, such as balance, coordination, information processing, and more. However, many police officers don’t consider that certain factors may interfere with the accuracy and reliability of these field sobriety tests. Such factors include:

  • Health problems
  • Balance issues
  • Weather conditions
  • Poor directions and/or test administration
  • Road conditions
  • Footwear
  • Time of day
  • Prescription medications

Not every police officer will pull drivers over on an even-surfaced road, in perfect weather, and away from oncoming traffic, nor will every officer ask drivers if they have underlying health conditions or take medications. As a result, SFST results may be flawed and inaccurate, framing a sober driver for DUI.

Types of SFSTs

The Standardized Field Sobriety Test is designed to test the normal use of mental and physical abilities, but it is severely flawed. The three tests within the SFST 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, which could cause them to be unable to smoothly track a moving object such as a pen or penlight. HGN tests are only 77% accurate.
  • Walk-and-turn test: Only 68% accurate, the walk-and-turn test requires suspects to first stand heel-to-toe with their arms relaxed at their side. A police officer will then instruct the person to take nine heel-to-toe steps along a straight line, and turn on one foot and do the same nine heel-to-toe steps in the opposite direction.
  • One-leg stand test: This test is often difficult for people, which explains why it’s only 65% accurate. The one-leg stand test requires DUI suspects to stand on one leg and raise their other leg six inches off the ground with both arms to the side. While doing so, officers will ask the person to count in thousands (one thousand one, one thousand two, etc.) for about 30 seconds or until the officer says to stop.

Unfortunately, police officers may fail to properly instruct drivers on how to take the field sobriety tests in question or incorrectly administer the tests. For instance, an officer giving an HGN test may not move the object smoothly in a horizontal direction, which may cause the driver’s eyes to jerk. Thus, that officer may assume the jerking of the eyeballs is correlated with impairment rather than their own faults.

It’s important to consider that people do not perform the functions demanded in the SFST in their everyday lives. Walking heel-to-toe and balancing on one leg can be challenging for anyone, even if they are sober. As such, “failing” one or more tests in the SFST does not indicate guilt.

Defending DUI Charges Across Santa Barbara

A DUI conviction could result in fines, jail time, license suspension, and humiliation. The consequences of a DUI are unlike other criminal penalties because a conviction will deprive you of your driving privileges and feeling of independence. Instead of letting the criminal justice system derail your livelihood, fight your charges with the help of our Santa Barbara criminal defense lawyers.

To speak with us about your situation, contact us online or at (805) 467-6060!