Motorists suspected of Driving Under the Influence (DUI) are routinely asked by law enforcement officers to perform one or more voluntary field sobriety tests (FST). These tests were developed by law enforcement agencies to assist officers in making roadside determinations as to whether a suspect is under the influence of alcohol or drugs.

Almost every criminal defense attorney will tell you NOT to attempt any FSTs. This is because many studies have concluded that the FSTs are "designed to fail". Refusing these tests will not result in avoiding the arrest, but it will assist your defense attorney later on down the road with your defense.

Only three tests have been "scientifically" studied and represented to have any measure of reliability in helping an officer predict whether a subject is above a certain legal limit (0.08 BAC, in California). These tests, known as the "standardized field sobriety tests", are sanctioned by the National Highway Traffic and Safety Administration (NHTSA) and include (1) the walk and turn [WAT] test, (2) the one leg stand [OLS] test, and (3) the horizontal gaze nystagmus [HGN] test. However, if these tests are not performed properly, or if conducted without adhering to the training protocols, such actions "compromise" the validity of the results.

The Walk-and-Turn (WAT) Test

The test has two distinct parts. The first part (instruction phase) requires the subject to balance heel-to-toe while the officer gives the instructions and demonstrates the test. The second part of the test requires the subject to take nine heel-to-toe steps on a straight line, pivot around, and take nine heel-to-toe steps back.

Test Conditions.

The required test conditions are level ground, a hard, dry, non-slippery surface, and conditions under which the suspect is in no danger should he fall. The student training manual states that the test criteria are not necessarily valid for people age 65 or older or people with leg injuries or inner ear disorders. (Prior editions of the manual stated this limitation as applicable to people more than 60 years of age, more than 50 pounds overweight, or with physical impairments that affect balancing ability. The reason for the change does not appear in the manual.) Suspects with heels more than two inches high must be given the chance to remove their shoes. The WAT test requires a line that the suspect can see and follow. If a natural line is not present, the officer must draw one in the dirt or on a sidewalk with chalk. Walking parallel to a curb is not acceptable. The suspect must be able to see to perform the test. His eyes must be open and adequate light available. The manual states that if the officer can see the suspect clearly the lighting is adequate, otherwise the officer must use a flashlight to illuminate the line. A person who cannot see out of one eye may have difficulty performing the test because of poor depth perception. The suspect must watch his feet because this makes the test more difficult for an intoxicated person. The officer must observe the suspect performing the test from three to four feet away and remain motionless. Standing too close or moving while the test is going on makes it more difficult even for a sober person to perform the test.

Standardized Test Procedures.

The WAT test must be administered as follows.

• Instruct the subject to place the left foot on the line and the right foot heel-to-toe in front of it (demonstrate).
• Verify that the suspect understands that the stance must be maintained while the instructions are given.
• If the suspect breaks from the stance during the instructions, stop the instructions until the stance is resumed.
• Tell the suspect that he will be required to take nine heel-to-toe steps down the line, turn around, and take nine steps back down the line but not to begin until instructed.
• Demonstrate two or three heel-to-toe steps and the turn.
• Instruct the suspect to keep both arms at his sides, watch his feet, count the steps out loud, and not to stop walking until the test is completed.
• Ask if the suspect understands the directions and, if not, repeat whatever he does not understand but not the entire set of directions.
• Tell the suspect to begin and to count his first step from the heel-to-toe position as one.
• If the suspect staggers, steps off the line, or stops while walking, allow him to resume from the point of interruption. Do not have him repeat the test from the beginning. (The manual states that the test loses its sensitivity if it is repeated.)

Standardized Scoring Clues.

The WAT test procedure has eight specific scoring clues the officer must track. The clues must be scored if the suspect:

• Loses balance during the instructions (his feet break from the heel-to-toe stance)
• Starts walking before the instructions are completed and he is instructed to start.
• Stops while walking to steady himself (but do not score this clue if he is only walking slowly).
• Leaves more than one-half inch between his feet during any heel-to-toe step.
• Steps off the line (if this occurs three times the test is terminated and the officer must score it as if all eight clues were shown).
• Raises one or both arms more than six inches from his side to maintain balance.
• Turns improperly either by removing the front foot from the line while turning, removes both feet from the line, or clearly does not follow the directions as demonstrated.
• Takes the wrong number of steps in either direction.

If the suspect cannot do the test, the officer must score it as if all eight clues were present.

If the suspect clearly exhibits two or more of the eight clues or cannot complete the test, the officer must classify his BAC as above .10%. Officers are instructed to note in their report how many times each clue appears, but count it only once for scoring purposes.

The One-Leg-Stand (OLS) Test

The OLS test requires a suspect to stand with his arms at his side and raise and hold one leg at least six inches off the ground for 30 seconds. He must count the seconds out loud according to specific instructions. The 30-second time period is important to the test since NHTSA research indicates that it makes the test sensitive to people in the .10% to .15% BAC range who might otherwise pass the test if they only had to maintain the position for less time. NHTSA research has shown that someone with a BAC above .10% can maintain balance for up to 25 seconds but seldom for 30 seconds.

Test Conditions.

The conditions required for the OLS test are like those for the WAT test. There must be light adequate to provide a visual frame of reference. The officer must observe motionless from three to four feet away for the same reasons as for the WAT test. The test criteria are not necessarily valid for people age 65 or older, people 50 pounds or more overweight, or people with leg injuries or inner ear disorders.

Standardized Test Procedures.

The NHTSA specified test procedures for the OLS test are as follows.

• Instruct subject to stand with feet together and arms down at sides (demonstrate).
• Tell subject not to start until told.
• Ask if subject understands instructions.
• Explain to the subject that when told to start he must raise one leg, either his left or right, approximately six inches off the ground with the toe pointed out (demonstrate stance).
• Tell the subject he must keep both legs straight with his arms at his side and, while holding the position count out loud for 30 seconds saying "one thousand and one, one thousand and two, etc." until told to stop (Demonstrate the counting method).
• Remind the subject he must keep both arms at his sides at all times throughout the test and keep watching his raised foot.
• Ask if he understands and get a confirmation of his understanding.
• Tell him to begin the test.
• Observe the subject from three feet away and remain "as motionless as possible." If he puts his foot down, instruct him to pick it up again and resume counting from the point it touched the ground. If he counts very slowly, end the test after 30 seconds. If he counts quickly, make him continue until told to stop.

Standardized Scoring Clues.

The test is scored according to four scoring clues. If the suspect

• Swaying side-to-side or back-and-forth while maintaining the one-leg stance
• Moving arms six inches or more from the sides to maintain balance
• Hopping in order to maintain the one-leg stance
• Putting his foot down one or more times during the 30 seconds.

If the suspect cannot do the test or puts his foot down three or more times, the officer must record the results as if all four clues were scored

Horizontal Gaze Nystagmus (HGN) Test

The HGN test is considered the most accurate of the three tests and NHTSA suggests that it be administered at a minimum if the suspect is unable to perform the other two tests due to age, size, or physical limitations. Some of the research on these tests suggests that when it is consistently given first in the test sequence, the reliance some police officers have on it might may have a subtle influence on his expectations and scoring of the other two tests (Anderson, Schweitz, and Snyder, Field Evaluation of a Behavioral Test Battery for DWI, DOT-HS-806-475, September 1983).

Nystagmus is involuntary jerking of the eye. Research shows that there are more than 40 types of eye nystagmus. The HGN test is designed to measure the type of nystagmus that occurs when the eyes gaze to the side. HGN will occur in any person's eyes when gazing extremely sideways, but NHTSA maintains that when a person is intoxicated there are these signs that become apparent in his eye movements: (1) the nystagmus occurs much sooner, that is, the less the persons eyes have to move before the jerking occurs; (2) if the person's eyes move as far to the side as possible, the greater the alcohol impairment, the more distinct the nystagmus will be at the extreme gaze position; and (3) an intoxicated person cannot follow a slowly moving object smoothly with his eyes. The HGN test is intended to identify and measure these three signs.

The key element of measuring HGN is correctly estimating when the eye has reached a deviation angle of 45 degrees. NHTSA maintains that when someone's BAC is above .10%, the jerking will begin before his eye has moved 45 degrees to the side. Officers trained with the NHTSA training procedure are provided a template for practicing how to estimate the 45 degree angle but they are not required to use a template when they administer the test in the field.

Test Conditions.

The test requires the use of an object for the subject to follow. The NHTSA training manual says that this can be a fingertip, penlight, or pen. It must be held slightly above eye level and 12-15 inches away from the person's nose. The police officer must inquire and make note of whether or not the suspect if he is wearing contact lenses, but the lenses do not have to be removed for the test. However, a suspect wearing glasses must be made to remove them.

Standardized Test Procedure.

The officer must administer the test following these procedures.

• The officer instructs the suspect that he is going to check his eyes, that he must keep his head still and follow the object only with his eyes, and that he must focus on the object until told to stop.
• The officer must hold the stimulus 12-15 inches from the suspect's nose and slightly above eye level. He must move the stimulus smoothly across the suspect's entire field of vision and check to see if the eyes are tracking together or one lags behind the other. (If the eyes do not track together, it could be a sign of a medical disorder, injury, or blindness.)
• The officer next must check to see that both pupils are the same size (if not, it could be a sign of a head injury).
• The officer starts with the left eye and smoothly moves the stimulus to the right at a speed such that it takes about two seconds to being the person's eye as far to the side as it can go. He then moves the stimulus similarly to the left to check the person's right eye.
• Using this process, the officer must check for all three clues in both eyes, always starting with the left. He must check at least twice for each clue in each eye.
• The officer must check for the clues in this sequence: lack of smooth pursuit, nystagmus at maximum deviation, and onset of nytagmus prior to 45 degrees.
• When checking for nystagmus at maximum deviation, the officer must move the stimulus to the side until no white is showing at the side of the suspect's eye and hold the position for four seconds.
• When checking for nystagmus onset angle, the officer must move the stimulus at a speed that would take about four seconds to reach the edge of the suspect's shoulder. Watch the eye for jerking and, when it occurs, stop and verify that is continues.
• The four-second speed of the stimulus movement is important. If the object moves too fast, the officer could go past the point of onset or miss it altogether.
• If the suspect's eyes start to jerk before 45 degrees, the officer must check to see that some white is still showing on the side of the eye closest to the ear. If no white shows, this means either that the officer has taken the eye too far to the side (more than 45 degrees) or the person has unusual eyes that do not deviate very far.

Standardized Clues.

There are three scoring clues that are measured for each eye, giving a maximum of six scoring points should all three clues be present in both eyes. If four or more clues are observed, the NHTSA manual states the person should be classified with a BAC above .10%. They are the scoring clues.

• Lack of smooth pursuit (the eyes bounce or jerk as they follow the object)
• Distinct nystagmus at maximum deviation when held for four seconds. While some people exhibit jerking at maximum deviation even when sober, in an intoxicated person the jerking should be "very pronounced, and easily observable."
• Onset of nystagmus before the eye has moved 45 degrees.

These are the only three clues NHTSA recognizes as valid indicators of HGN. NHTSA specifically does not support the position that the exact onset angle can be used to estimate a person's specific BAC and considers this to be a misuse of the HNG test.