A Brief Guide to the Different Types of Field Sobriety Tests

As explained above, some FSTs are recognized by the National Highway Traffic Safety Administration (NHTSA). They include the following: 

• Horizontal Gaze Nystagmus (HGN) Test

• Walk-and-Turn Test

• One-Leg Stand Test

These tests examine and evaluate indicators of impairment such as eye movements, balance, and ability to follow instructions. 

Horizontal Gaze Nystagmus Test

Nystagmus refers to involuntary jerking eye movements when your eyes move from side to side, up-down, or in a rotatory motion. When drunk, nystagmus can become accentuated. People under the influence of alcohol or drugs may have trouble visually monitoring a moving object.

During this test, the officer horizontally moves an object, such as a pen or flashlight, and asks you to follow it with your eyes. The officer will look for three signs of impairment: 

• When the eyes are “at maximum deviation,” they twitch sharply.

• You are unable to maintain a steady track of the moving item.

• Your eyes begin to twitch within 45 degrees of the center.

One-Leg Stand Test

The officer will advise you to stand with one foot lifted roughly six inches parallel to the ground. At the same time, the officer will ask you to count loudly until told to stop. The officer looks for four signs of impairment: 

• Swaying

• Balancing using the arms

• Hoping to preserve equilibrium

• Inability to balance, for example, putting a foot down

Walk-And-Turn Test

The officer instructs you to take nine heel-to-toe steps down a straight line. You then turn on one foot and return nine steps in the other direction. The officer looks for seven symptoms of impairment during the exam. Disqualification occurs when you: 

• Begin before the instructions have been completed

• Cannot maintain balance while listening to instructions

• Do not have heel-to-toe contact

• While turning, lose equilibrium

• Stop walking to recover equilibrium

• Take the wrong number of steps

• Use your arms to balance

Other Non-Standardized Tests

Police officers occasionally use non-standardized field sobriety tests to charge drivers with DWI. Examples of other tests include: 

• Romberg Balance Test

• Asking suspects to write or recite the alphabet to assess for impairment. 

• Instructing individuals to count backward. 

These tests have not been scientifically proven to assess impairment. 

These tests are subjective. It is possible to challenge them in court to weaken the prosecution’s case. For example, police officers undergo a brief training program to administer these tests. Failed tests can result from incorrect instructions, missing steps, or confusion. A fair evaluation requires adequate observation of the test participant. Many factors can contribute to failed tests. They include the following: 

• Age

• Anxiousness 

• Clothing

• Flashing police lights 

• Illness

• Lack of illumination 

• Medical issues

• Medicines

• Physical injuries

• Rapid traffic

• Shoes

• Temperature or weather 

• Uneven terrain 

• Weight

Adequate training is crucial for administering sobriety tests. You can weaken the prosecution’s case by proving that the administering officer was not adequately trained. Or you could show that they failed to follow standardized procedures.