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Field Sobriety Test Information

The field sobriety tests that an officer subjects an individual to when stopped for the suspicion of DUI are very subjective in nature. These tests were designed to be failed.

The majority of people are not aware that these tests are optional and that you are not required to submit to them. The officer who administers the tests is certainly not going to tell the accused that the field sobriety tests are optional.

If you find yourself in a DUI situation, you may politely refuse these tests when an officer asks you to perform them.

The three main tests that make up the Standardized Field Sobriety Tests or (SFST) are:

  • Horizontal Gaze Nystagmus (HGN)
  • Walk-and-Turn
  • One-leg Stand

- HGN Test Procedure

(HGN) or horizontal gaze nystagmus is an involuntary jerking of the eye which naturally occurs as the eyes move from side to side. Nystagmus occurs when the human eyes rotate at high peripheral angles.

When an individual has been drinking and is impaired by alcohol, nystagmus is exaggerated and in most cases occurs at lesser angles. A person impaired by alcohol will also not be able to smoothly track a moving object with their eyes from side to side.

When administering the HGN test the officer is watching the eyes of the suspect while the suspect follows a slow moving object like a pen, horizontally with their eyes. The officer is looking for three indicators of impairment in the suspects eyes:

  • If the eyes cannot follow a moving object horizontally.
  • If jerking is distinct when the eyes are at their maximum deviation.
  • If jerking occurs within 45 degrees of center.

If the officer registers four or more clues between both of the suspects eyes, more than likely the suspect has a blood alcohol content (BAC) of 0.10 or greater. The NHTSA says that this test shows proper classification as to whether or not a suspect has a blood alcohol content of greater than 0.10 approximately 77 percent of the time.

- Walk-and-Turn Test Procedure

In the walk-and-turn test, the officer directs the suspect to take nine steps in a row going from heel-to-toe with each step, along a straight line. After the suspect has taken the steps, they then must turn on one foot and return to where they started in the same manner.

The officer is looking for seven indications of impairment, those indicators are:

  • If the suspect cannot keep their balance while listening to the officers instruction.
  • The suspect begins before the officer finishes his instructions.
  • Suspect stops while walking the line to regain their balance.
  • Does not touch heel-to-toe with each step.
  • Uses their arms for balance.
  • Suspect loses their balance while turning.
  • Suspect takes the incorrect number of steps.

The NHTSA says that 68 percent of individuals who exhibit two or more indicators from the above list while performing this test will have a BAC of 0.10 or greater. To find out how many drinks it will take to reach a blood alcohol content of 0.10 checkout our freeBAC calculator.

- One-leg Stand Test Procedure

In the one-leg stand test, the officer instructs the suspect to stand with one foot raised approximately six inches of the ground and to count by thousands (one thousand-one, one thousand-two, etc.) until the officer tells the suspect to put their foot down. While the suspect is performing this test, the officer is timing the suspect for 30 seconds.

The officer is looking for four indications of impairment, those indicators are:

  • Swaying while balancing on one foot.
  • Suspect is using their arms for balance.
  • The suspect is hopping to maintain their balance.
  • Suspect is putting their foot down during the test.

The NHTSA says that 65 percent of individuals who exhibit two or more indicators from the above list while performing this test will have a BAC of 0.10 or greater.

The more indicators that the officer receives during the field sobriety tests, the more convincing the testimony will be in court. Since the SFST is administered according to national standards, the SFST has greater credibility in court.

Alternative Testing Methods

When an officer stops a suspect who is disabled, who cannot perform the standardized field sobriety tests, the officer will administer other tests such as counting aloud, reciting the alphabet or finger dexterity tests.

While here it is important to review your states DUI Laws to become familiar with them.