Field Sobriety Tests Defense


Field Sobriety Tests or FSTs are designed to evaluate a person’s ability to divide his/her attention according to the California Highway Patrol. This means Field Sobriety Tests require a person to concentrate on several things at once.

To drive a car we concentrate on several things at once or divide our attention among different tasks:  react appropriately to a constantly changing environment while controlling steering, acceleration, and braking.  Therefore, there should be a correlation between the divided attention tasks and driving.  Not so fast! Just because the rooster crows when the sun comes up, does not mean the rooster crowing caused the sun to rise.

Alcohol and other drugs reduce a person’s ability to divide attention. The Highway Patrol Manual says even when under the influence of alcohol, people can handle a single focused attention task fairly well. For example, a driver may be able to keep her car within the lane as long as the road is straight when the road curves, however, the impaired driver may not and run off the road.

The government has applied the concept of divided attention to Field Sobriety Tests. Prosecution and law enforcement believe Field Sobriety Tests simulate the divided attention characteristics of driving. They point out to operate a vehicle safely you must exercise the following mental and physical capabilities:

(1) Information processing.

(2) Short-term memory.

(3) Judgment and decision making.

(4) Balance.

(5) Steady, sure reactions.

(6) Clear vision.

(7) Small muscle control.

(8) Coordination of limbs.

Field Sobriety Tests require a person to demonstrate at least two or more of these capabilities simultaneously. Prosecutors and law enforcement claim FSTs are simple. This is wrong.  They claim an average person should have no difficulty performing the tests when sober. However, this is also not true.

Do you remember the last time you walked heel-to-toe while driving, or raised your foot six inches off the ground, kept your arms down at your sides and counted aloud by thousands?

In a scientific article published for peer-review in 1994, “Field Sobriety Tests: Are They Designed for Failure?” authors Spurgeon Cole and Ronald H, Nowaczyk sum up the problem:

The fact that these tests are largely unfamiliar to most people and not well practiced may make it difficult to perform them.”

Cole and Nowaczyk reported experienced police officers judged 46.5% of completely sober subjects videotaped performing psychomotor field sobriety tests to be impaired.

Field Sobriety Tests – What does Standardized mean?

The Standardized Field Sobriety Tests were developed in the mid 1970s under contract from the National Highway Traffic Safety Administration. (NHTSA).

NHTSA sponsored 3 studies: 1) Colorado 1995, 2) Florida 1997, 3) San Diego 1998.

No NHTSA study has been published in a peer-reviewed journal.  Articles submitted to scientific journals are usually peer-reviewed.  The peer-review process allows other scientists to critique the method and conclusions reached by the articles authors.


In the 1998 San Diego study by NHTSA), entitled, Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent, the authors write: 

“Many individuals, including some judges, believe that the purpose of a field sobriety test is to measure driving impairment. …The reasoning is correct, but it is based on the incorrect assumption that field sobriety tests are designed to measure driving impairment.”

The Standardized Field Sobriety Tests battery includes these “tests”:

(a) Horizontal Gaze Nystagmus (HGN):  The California Highway Patrol Manual says this test should be used only by officers who have received formal training in its administration. HGN is not a psychophysical test. The clues associated with HGN are not designed to be considered “signs of impairment.”  The NHTSA Manual says, “Horizontal Gaze Nystagmus is an involuntary jerking of the eye that occurs naturally as the eyes gaze to the side.” Under normal circumstances, nystagmus occurs when the eyes are rotated at high peripheral angles.  However, when impaired by alcohol, nystagmus is exaggerated and may occur at lesser angles. A person impaired by alcohol will also often have difficulty smoothly tracking a moving object.  In the HGN test, the officer looks at your eyes as you follow a slowly moving object such as a pen or tip of his finger, horizontally with your eyes. The cop looks for 3 clues in each eye:  if your eye cannot smoothly follow a moving object, if jerking is distinct and sustained when your eye is at maximum deviation, and if the angle of onset of jerking is prior to 45 degrees of center.  NHTSA research also admits HGN may also indicate consumption of seizure medications, phencyclidine, a variety of inhalants, barbiturates, and other depressants.

(b) Walk and Turn:  The California Highway Patrol Manual says the Walk and Turn SFST is considered to be the most sensitive psychophysical test.  The NHTSA Manual says, in the Walk and Turn test, the cop must instruct you to place your left foot on the line and demonstrate.  The cop must, then, instruct you to place your right foot on the line ahead of your left foot, with the heel of your right foot against the toe of the left foot and demonstrate.  The cop must, then, instruct you to place your arms down at your sides, and demonstrate.

The cop must, then, instruct you to take nine heel-to-toe, steps, turn, and take nine heel-to-toe, steps back, and demonstrate 3 heel-to-toe, steps.  The cop must, then say, “When you turn, keep your front foot on the line, and turn by taking a series of small steps with the other foot, like this.” The officer is required to demonstrate.  The officer must also tell you, “While you are walking, keep your arms at your sides, watch your feet at all times, and count your steps out loud.”  She must also instruct, “Once you start walking, don’t stop until you have completed the test.”  The police officer looks for a maximum of 8 clues with a decision point of 2: cannot keep your balance while listening to the instructions, beginning before the instructions are finished, stopping while walking, not touching heel-to-toe (more than one-half inch), stepping off the line (one foot is entirely off the line), using your arms to balance (more than 6 inches), improper turn (spins or pivots), or taking the incorrect number of steps.

(c) One-Leg-Stand:  The California Highway Patrol Manual says the One-Leg-Stand divides the subject’s attention among such “simple” tasks as balancing, listening, and counting out loud.  The NHTSA Manual says in the One-Leg Stand test, the officer must instruct you to stand with one foot approximately six inches off the ground, keeping your foot parallel to the ground, and count aloud by thousands (One thousand and one, one thousand and two, etc.) until you are told to stop. The officer must tell you to keep your arms at your sides at all times and to keep watching your raised foot.  The officer will time you for 30 seconds. The officer looks for 4 clues with a decision point of 2:  swaying while balancing, using arms to balance (six inches or more), hopping to maintain balance, and putting your foot down.

Marijuana DUI Cases

The Standardized Field Sobriety Tests do not mean the same thing with marijuana DUIs as they do with DUI alcohol. Horizontal gaze nystagmus (HGN) is not present unless there is also alcohol impairment, and the One-Leg Stand and Walk and Turn tests are not clear indicators of either impairment or lack of impairment at lower doses.

Spurgeon Cole and Ronald H, Nowaczyk specifically caution about the 1977 NHTSA study in their scientific article published in 1994, “Field Sobriety Tests: Are They Designed for Failure?”  saying “false alarms are a concern” of divided attention field sobriety testing.

 “In the 1977 study, 47 % of the subjects who would have been arrested based on test performance actually had a blood alcohol concentration (BAC) lower than .10 percent, the decision level used by the officers.”

The authors further conclude:

“Problems in scoring can be attributed, in part, to the lack of standardization across many field sobriety test studies.  In addition, a few miscues in performance can result in an individual being scored as impaired. For example, a person is viewed as impaired for missed two of nine points on the walk-and-turn test or two of five points on the one-leg stand test.  The stringent scoring criteria as well as potential subjectivity in determining whether a point should be awarded may account for accuracy rates that vary from 72 to 96 percent amount police agencies…”

Two other scientific studies were performed under contract from National Highway Traffic Safety Administration to study the three FSTs within a laboratory controlled environment and within a field environment (The 1981 study: Development and Field Test of Psychological Tests For DWl Arrest; The 1983 study: Field Evaluation of a Behavioral Test Battery For DWl).

Why Field Sobriety Tests Must Be Standardized

The validity of SFST results depends upon law enforcement following established, standardized procedures for test administration and scoring. National Highway Traffic Safety Administration’s Standardized Field Sobriety Test Student Manual clearly describes how the “tests” should be administered under ideal conditions, but ideal conditions rarely exist in the field.  Therefore, DUI Attorneys should carefully and thoroughly investigate where police officers gave these so-called tests and how they scored the results.

The NHTSA Standardized Field Sobriety Test Student Manual also says, “variations from ideal conditions, and deviations from the standardized procedures, might affect the evidentiary weight that should be given to test results.”  This means the judge will admit the FST results, but a skilled DUI Attorney is able to highlight the unfairness in these so-called tests.

Were you on a gravely, wet, slanted road with traffic whizzing by you?  Did you get a chance to practice for the test?  Were you nervous?  Did you tell the cop you had an injury, but he or she said “go and ahead and do it anyway.”

The International Association of Chiefs of Police (IACP) adopted uniform procedures in 1992 to guide the training of Standardized Field Sobriety Test instructors and practitioners. Those standards include 24-hours of NHTSA-approved Standardized Field Sobriety Test instruction. The procedures for administering and interpreting SFST results can be readily learned and, generally, you get better with experience.  However, it is very possible for SFST skills to get worse if  not exercised regularly (e.g., absence from patrol work).  Also, the SFST procedures have evolved since 1981.  Changes to the procedures could likely result in an officer giving SFSTs according to outdated protocols.  Therefore, NHTSA recommends law enforcement agencies conduct refresher training for SFST instructors and practitioners.

Richard Wagner is one of the few California DUI defense attorneys who has undergone NHTSA-approved Standardized Field Sobriety Tests (SFST) instruction. He was certified in the procedures for administering and interpreting SFSTs. Call 714-721-4423 or contact to discuss your DUI.