Field Sobriety Tests (FSTs)

Also known as the “Walk-the-Line” test or the “Walk-and-Turn” test, this test is the most common of all the Field Sobriety Tests

The Heel-to-Toe test combines two tasks:

• Standing on a line (can be imaginary straight line) heel-to-toe.
• Maintaining balance while walking a line heel-to-toe.

The Heel-to-Toe test is an excellent test for divided attention impairment testing the subject’s ability to process information. Divided attention impairment involves a person’s ability to perform 2 or more acts — both mental and physical –at one time. It is widely accepted that balance and coordination are affected after the primary mental functions need for driving are affects. Consequently, when balance and coordination (physical acts) have been impaired by alcohol, a person’s ability to process information, divide attention, and assess performance (mental acts) has already been impaired also.

This test requires a division of attention between five tasks:

1. Maintaining a heel-to-toe position with arms at side while listening to instruction.
2. Maintaining balance while walking a straight line heel-to-toe
3. Keeping arms at sides.
4. Counting steps aloud.
5. Maintaining balance when turning to change direction.

Test Instructions

• The suspect should put one foot on the line and the other foot behind it with the heel touching the toe.
• When the suspect assumes this position, the officer should continue with instructions. The subject should then be told to take a pre-instructed number of heel-to-toe steps down the line, turn around and take a pre-instructed number of heel-to-toe steps back.
• The suspect should keep his/her hands at their sides, watch their feet at all time, and count each step aloud. The officer should ensure the subject understands the direction prior to continuing. The subject should begin and count the first step form the heel-to-toe position as “one.”
• The suspect should make the turn by keeping one foot on the line and then use the other foot to step around.

Symptoms of Intoxication

• Loses balance during instructions by not maintaining heel-to-toe position throughout instructions.
• Starts before instructions are completely explained.
• Stops while walking or pauses for several seconds after a stop.
• Does not touch heel-to-toe or leaves a gap between heel and toe on any step.
• Subject steps to the side (off the line) in order to maintain balance
• Raises arms to balance.
• Loses balance while turning.
• Takes more or less than the pre-instructed number of steps in each direction,
• Cannot do the test. Steps off the line several times, is in danger of falling, or otherwise demonstrates inability to complete the test.

Also known as the “Standing on One Foot” test or tile “One-leg Stand” test.

Test Instructions

• The suspect should be told to stand with his/her heels and toes together, arms down at their sides, raise one foot approximately six inches off the ground, and hold that position for approximately 30 seconds while counting from 1001 to 1030. A high-tolerance drinker at a BAC below 0.15 percent may be able to maintain his/her balance for 20-25 seconds but will likely falter after that time period; thusly, it is recommended that the suspect count aloud from 1001 to 1030 in order to estimate 30 seconds.
• The officer should demonstrate the test, ensure that the suspect understands the directions, and should not continue until the subject indicates understanding.

Symptoms of Intoxication

• Sways side-to-side or back-and-forth while balancing.
• Raises arms to balance.
• Able to keep one foot off the ground, but resorts to hopping to maintain balance.
• Puts foot down one or more times during 30-second count; not able to maintain one leg stand position.

This is one of the most sensitive FSTs available. By using this test it is possible for a trained officer to estimate a suspect’s BAC within plus or minus 0.02 percent of the chemical test results, but the test does have limitations. These limitations are why it is to be used in conjunction with other accepted FSTs.

Nystagmus is the rapid involuntary oscillation of the eyeballs. This oscillating movement may be horizontal, vertical, rotatory, or mixed. Nystagmus may be due to causes other than alcohol. These other causes include seizure, medications, phencyclidine, inhalants, barbiturates, and other depressants. A large disparity between the performance of the right and left eye may indicate brain damage Nystagmus as it relates to alcohol is Horizontal Gaze Nystagmus. It occurs in approximately 50% of all individuals without alcohol ingestion if they move their eyes to the lateral extremes (45% to 65% from straight ahead); however, after a person consumes alcohol the onset of the Horizontal Gaze Nystagmus occurs at a much smaller angel, depending on the BAC As the BAC increases, the lateral extremes usually become very pronounced and smooth pursuit eye movements are interrupted.

Test Instructions

• Eyeglasses should he removed since they may block the officer’s view of the suspect’s eyes. In addition, hard contact lenses may restrict the boundaries of movement of the eyes, which may prohibit recognition of borderline cases.
• A stimulus should be positioned slightly above the eyes and about 12-15 inches away. The stimulus can be as simple as the tip of an index finger, a pen or pencil, or a penlight. A penlight makes an excellent stimulus at night. Placing the stimulus slightly above the eyes will elevate them and reduce squinting.

Symptoms of Intoxication

• The inability of the eyes to follow smoothly
• The angle of onset of Horizontal Gaze Nystagmus
• The extent of nystagmus at the maximum lateral deviation.