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Are Field Sobriety Tests Accurate?

Most people are familiar with field sobriety tests. They may have taken one themselves, but these tests are commonly seen in TV shows and movies.

Although these methods may seem like safe, standard, and accurate ways to determine whether someone is intoxicated, you’d be surprised to know that they can be notoriously inaccurate. But despite their inaccuracies, Texas law enforcement continues to implement these tests when making driving while intoxicated (DWI) arrests.

Standard Field Sobriety Tests in Texas

The National Highway Traffic Safety Association (NHTSA) supports the use of three standardized tests when making a DWI stop and arrest:

  • One-leg stand (OLS)
  • Walk and turn (WAT)
  • Horizontal gaze nystagmus (HGN)

When law enforcement officers perform these tests, they look for specific results to determine whether you might be under the influence or intoxicated by alcohol or drugs.

One-Leg Stand

In a one-leg stand test, officers will ask a driver to stand straight with feet together and arms to the side. Upon request, the driver has to raise a single leg at least six inches and hold it in place until asked to stop.

Some things officers look for in this test include:

  • Moving and swaying
  • Jumping on one foot
  • Failing to keep one leg up
  • Using arms to provide balance

Though this seems like a straightforward test, anyone can potentially fail for reasons unrelated to intoxication, such as medical conditions, nervousness, or environmental conditions.

Walk and Turn

The walk and turn test asks drivers to walk in a straight line, connecting heel-to-toe with each step. After several steps are taken, officers usually ask the individual to turn around and return in the same manner.

Officers look for the following to determine intoxication:

  • Loss of balance
  • Pausing mid-test
  • Not touching heel-to-toe
  • Not taking the correct number of steps
  • Starting the test too soon

Similar to the one-leg stand test, numerous factors could contribute to someone failing this test while sober, such as the fear of dangerous traffic conditions or even a person’s weight.

Horizontal Gaze Nystagmus (HGN)

Nystagmus is a medical term for irregular, involuntary movements made by the human eye. Normally, these movements happen when a person looks too far to the sides. When a person is intoxicated, this type of jerking movement can occur much more often.

During the HGN test, an officer usually holds an item and asks the driver to follow it with their eyes, checking to see whether the driver’s eye movements are too erratic.

Unfortunately, people can suffer from conditions like vertigo and labyrinthitis that cause them to have nystagmus naturally, regardless of intoxication.

Can an officer compel you to perform these tests in Texas?

In Houston and across Texas, field sobriety tests are completely voluntary. This means that you are not legally obligated to participate in them if asked. Also, you cannot face legal penalties for refusing to take a field sobriety test.

Field Sobriety Tests Are Inaccurate in Many Cases

Per the NHTSA guidelines, field sobriety testing is supposed to be done under ideal conditions. Unfortunately, in the majority of cases, field sobriety tests are conducted on the sides of roads and highways. This can mean that speeding cars, inclement weather, uneven surfaces, and other environmental factors can seriously affect the outcomes of the tests.

In the end, poor test conditions can lead to poor results. Additionally, not everyone will react the same way to these tests. Medical problems, language barriers, mental health concerns, fear and anxiety, and even the type of footwear worn by the driver can contribute to inaccurate results. Officers may also fail to give accurate instructions, count wrong, or be poorly trained.

As such, because so many factors can play into bad results, field sobriety tests cannot always be trusted.