Dallas DWI Lawyer – Articles

Standardized Field Sobriety Tests – What You Should Know

If a Police officer has “reasonable suspicion” of DWI, the officers will use 3 standardized field sobriety tests in conducting their DWI investigation: the Horizontal Gaze Nystagmus (HGN), Walk and Turn, and One Leg Stand tests. You have the right to refuse taking each of these tests.
Understand the Police want you to help them make their case against you stronger. By performing field sobriety tests, you are simply helping the Police manufacture evidence against you. Be aware that they fully intend on using this evidence against you in court. The tests and the clues the Police are looking for are as follows:

1. HGN – the Horizontal Gaze Nystagmus has a 77% reliability of predicting that a person is above the legal limit. However, all of the proper instructions must be given to you for the test to be reliable. You must be told the following:

  • I am going to check your eyes
  • Keep your head still and follow this stimulus with your eyes only
  • Keep following the stimulus with your eyes until I tell you to stop

The officer will hold the stimulus out to the right then the left, requiring your eyes follow the stimulus as they look for nystagmus (jerking of the eye).

There are six scoring factors for the HGN test (one for each eye):

  • The Lack of Smooth Pursuit: The eyes bounce as they follow a smoothly moving stimulus
  • Distinct Nystagmus at Maximum Deviation: Distinct nystagmus will be evident when the eye is held at maximum deviation for a minimum of four seconds
  • Onset of Nystagmus Prior to 45 Degrees – They are looking for the point at which the eye is first seen jerking

2. Walk & Turn – all of the proper instructions must be given to you for the test to be reliable. You must be told the following, and the officer must demonstrate as he is instructing you:

  • Place your left foot on the line
  • Place your right foot on the line ahead of your left foot, with the heel of your right foot against toe of your left foot
  • Keep your arms to your side
  • Keep this position until you are told to begin
  • The officer must ask if you understand the instructions and receive an acknowledgement from you that you do
  • When told to start, take 9 heel-to-toe steps, turn, and take 9 heel-to-toe steps back
  • When you turn, keep the front foot on the line, and turn by taking a series of small steps with the other foot
  • While walking, keep arms at side, watch feet at all times, and count steps out loud
  • Once you start, don’t stop until test is completed
  • The officer must ask if you understand the instructions and receive an acknowledgement from you that you do
  • Begin the test and count first step from the heel-to-toe as “one”

There are eight scoring factors for the Walk and Turn test:

  • Cannot keep balance while listening to instructions
  • Starting before instructions are finished
  • Stopping while walking
  • Did not touch heel-to-toe (more than 1/2 inch on any step)
  • Stepped off line
  • Used arms for balance
  • Improper turn
  • Incorrect number of steps

3. One Leg Stand – all of the proper instructions must be given to you for the test to be reliable. You must be told the following, and the officer must demonstrate as he is instructing you:

  • Stand with your feet together and your arms at your side
  • Keep that position until you are told to begin
  • Third point
  • The officer must ask if you understand the instructions and receive an acknowledgement from you that you do
  • When told to start, raise either leg approximately 6 inches off the ground with your foot pointed out
  • Keep both legs straight, arms at side
  • Count 1,001, 1,002 etc. until told to stop
  • Keep your arms at side and keep watching raised foot
  • The officer must again ask if you understand the instructions and receive an acknowledgement from you that you do
  • The officer will then start the test
  • The test can last no more than 30 seconds of actual time

There are four scoring factors for the one leg stand test:

  • Sways while balancing
  • Arms for balance
  • Hopping
  • Puts foot down

If you put your foot down three or more times, you are considered to have reached a “decision point” on the testing. If you stop at any point during the testing, you should be given the opportunity to resume the testing.

While there are many DWI attorneys in Dallas, you should contact Mark T. Lassiter for tough, aggressed, and trusted DWI defense.


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