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Field Sobriety Test and Their Validity

Posted: July 25, 2015 Category: Legal Update

If you are stopped for DWI in Texas, law enforcement officers will ask that you perform certain field sobriety tests. One of the first things to remember is that you do not have to do them! You can refuse and will not be ticketed for your refusal.

However, if the officer does not remind you of this right and you must perform them, we want to give you the details on what these tests are and how they should be carried out. If any of these steps are missed or the officer does not demonstrate them, you could have a case that the test be thrown out in court.

The following three tests have been sanctioned by the National Highway Traffic Safety Administration:

One Leg Stand

Performed properly, this test has a 65% reliability in predicting whether a person’s BAC is over the legal limit. If any of these instructions are not given, you may have the test thrown out in court.

  1. Stand with your feet together and arms at your side. Keep that position until you are told to begin. The officer must also ask if you understand the instructions and receive your acknowledgement.
  2. When told to start, raise either leg about 6 inches off the ground with your foot pointed out, keeping both legs straight and your arms at your side.
  3. Count 1,001, 1,002, etc. until told to stop, while keeping your leg raised and watching your foot.
  4. This test should not last more than 30 seconds.

Officers are looking for any swaying while balancing, use of your arms for balance, hopping or having to put your foot down.

Walk and Turn Test

The second test is the Walk and Turn Test, with a 68% reliability at predicting a subject’s BAC. Again, the officer must give you these instructions and receive acknowledgment of your understanding before you can proceed.

  1. Place your left foot on the line, with your right foot ahead of your left foot, heel-to-toe, while keeping your arms to the your side.
  2. When told to start, take 9 heel-to-toe steps, turn, and take 9 heel-to-toe steps back.
  3. As you turn, keep the front foot on the line and turn by taking a series of small steps with the other.
  4. Keep your arms to your side, watch your feet at all times, and count your steps out loud.

Officers are looking for several factors, including your ability to keep balance while listening to the instructions, starting before you are told to, stopping while walking, not touching heel-to-toe or stepping off the line, using your arms to balance, turning incorrectly or not doing the right number of steps.

Horizontal Gaze Nystagmus

The third test, when instructed properly, has a 77% reliability of predicting that a person’s BAC is over the legal limit. Officers must give these instructions properly for the test to be reliable:

  1. Officer says, “I am going to check your eyes.”
  2. As the stimulus is in your line of vision, keep your head still as you follow the stimulus.
  3. Officer says, “Follow the stimulus with your eyes until I say to stop.”

There are three major scoring factors that officers are looking for, one for each eye, totaling to six scoring factors. These factors include eyes “bouncing” as they follow the stimulus, uncontrolled eye movement, called “nystagmus”, and nystagmus beginning before the stimulus is 45 degrees out of your line of vision.

With the lack of scientific validity and opportunity for error with many of these tests, it is imperative that you know your rights. If you feel that your field sobriety test was flawed in your DWI case, give the Law Office of Carlo Key a call and let us fight for your fair verdict.

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