Field Sobriety Tests are a Fraud on the Public

Standardized Field Sobriety Tests – Why you should never do them: If a law enforcement officer  has reason to suspect that a person has been driving under the influence, the officer will likely ask the person to perform field sobriety tests. Field sobriety tests are voluntary and no person is required to perform them, however the officer will not tell you that the tests are voluntary.  If a person agrees to perform the field sobriety tests, he or she will be evaluated by the officer on how he or she performs and reacts during the testing.

Standardized Field Sobriety tests are validated, which means that the test must be administered in a precise way for the results to have any validity. If the officer fails to administer the test exactly as they are designed to be administered, then the results are compromised.

In addition, often times the officer will have the driver perform field sobriety tests that are not validated. It requires a DUI defense attorney that is trained in field sobriety tests to evaluate what tests were given to a driver and whether the tests were administered correctly or not, and what the results mean, if anything.

DUI Defense Attorney Manuel J. Barba is a nationally recognized Standardized Field Sobriety Test Instructor, having completed the National Highway Traffic Safety Administration (NHTSA) / International Association of Chiefs of Police (IACP) DWI Detection Standardized Field Sobriety Testing Instructor Program, and has taught Standardized Field Sobriety Test courses throughout the United States.  Attorney Barba is also trained in Drug Recognition Expert (DRE) protocols.

Although attorney Manuel J. Barba is a Standardized Field Sobriety Test Instructor, he has also studied the flaws associated with the development of field sobriety tests as well as the unreliability of these tests.  The following is a discussion regarding the unreliability of the Standardized Field Sobriety tests and why persons should NEVER agree to perform the tests.

Development of the Standardized Field Sobriety Tests

During the late 1970s, the National Highway Traffic Safety Administration (NHTSA), an arm of the U.S. Department of Transportation, commissioned the Southern California Research Institute in Los Angeles to research and develop standardized field sobriety tests (SFSTs) so that law enforcement officers had some sort of uniform tools they could use to try to determine if a driver was above the legal limit of blood alcohol content (BAC).

These physical tests were designed to be performed on the side of the road by an individual suspected of driving under the influence (DUI).  In theory, the law enforcement officer administers each test in a standardized manner – this means that the officer is to administer each field sobriety test using specific procedures, and then the officer will observe the driver’s performance, using standardized clues to score the individuals performance, and then make a determination of whether the driver has a blood alcohol concentration above the legal limit, and is thus is too impaired to safely drive the motor vehicle.

The reality is that the so called “science” and methods used in developing these tests have serious flaws that render the tests invalid and unreliable. Furthermore, blood alcohol concentration does not necessarily correlate to impairment as a general rule and, in some individuals, there is no correlation whatsoever.   In other words, some persons that are alcohol free cannot perform the field sobriety tests correctly, while other persons who have been drinking alcohol can perform the tests flawlessly.

Flaws with the SFST Studies

The problem:  the NHTSA-commissioned studies and the subsequent reports, did not include analysis from medical professionals such as neurophysiologists, neurologists, ophthalmologists, as well as biomechanical engineers – an important factor that would have discovered the possible flaws of the tests.   In addition, there was no explanation provided by NHTSA as to why it chose psychologists to conduct these experiments.  Although it is true that these tests have some mental aspects, they are largely physical performance tests in nature.

The development of the three test Standardized Field Sobriety Test (SFST) battery consisted of intricate ocular movements, balance, vestibular function, proprioception, vision, and neurological function.   Despite this, these tests were designed to be conducted by police officers who have no formal education in any of the aforementioned areas, on the side of the road, and usually at night.  In reality, most law enforcement officers have only attended a 2- to 3-day seminar – that’s it. For a complete understanding of the standardized field sobriety tests, one must have knowledge of the above-mentioned disciplines and how those areas of study have evolved in the last 30 years.

Surprisingly, NHTSA does not release raw data from the standardization trials or field studies (I wonder why?).  However, what is obvious from reviewing the reports on the studies is a flawed experimental design and a failure to follow the most basic scientific procedures.  For example, the NHTSA studies lacked control groups, the studies did not randomize subjects and conditions, the studies did not perform prior screening of test subjects to determine whether they were ever able to demonstrate good performance in these exercises, the studies did not undergo a scholarly peer review, and the data from the studies were not published with the reports.   The most disturbing aspect of the NHTSA studies was that although the authors claimed to be developing field sobriety tests to determine blood alcohol concentration, actual blood alcohol concentration was never tested.  The studies instead relied on breath testing devices that are generally inaccurate when performed before a person has fully absorbed the consumed alcohol.  Since breath alcohol testing has a high margin of error, these SFST studies likely produced unreliable results.

The Three SFST Test Battery

The three tests determined to be the most reliable, which were later termed Standardized Field Sobriety Tests in the NHTSA literature, are the Horizontal Gaze Nystagmus (HGN) , the Walk and Turn (WAT), and the One-Leg Stand (OLS) tests.

Horizontal Gaze Nystagmus Test:

According to the NHTSA:

“Nystagmus is an involuntary jerking or bouncing of the eyeball… Horizontal gaze nystagmus (HGN) refers to a lateral or horizontal jerking when the eye gazes to the side. In the impaired driving context, alcohol consumption or consumption of certain other central nervous system depressants, inhalants or phencyclidine, hinders the ability of the brain to correctly control eye muscles, therefore, causing the jerk or bounce associated with HGN. As the degree of impairment becomes greater, the jerking or bouncing, i.e. the nystagmus, becomes more pronounced. This is assessed in the horizontal gaze nystagmus test.”

“The HGN test is very easy to administer. The officer must administer the test in a way that ensures that the subject’s eyes can be seen clearly, i.e., in a well lit area or by use of a flashlight to illuminate the subject’s face. The subject should not face toward the blinking lights of a police cruiser or passing cars, which may cause optokinetic nystagmus. The subject does not have to be standing but can be sitting down.

The law enforcement officer informs the subject “I am now going to check your eyes.” The officer is not “testing” the subject’s vision, as an ophthalmologist would, but instead, the officer is “checking” the eyes for the physical manifestation of HGN.”

“The HGN test requires only an object for subjects to follow with their eyes, such as a pen or the tip of a penlight. The officer places the object approximately twelve to fifteen inches from the subject’s face and slightly higher than eye level. Placing the object above eye level opens the subject’s eyes further and makes their movement easier to observe.” “The officer instructs the subject to follow the object with the eyes and the eyes only; the head should remain still.”

When performing the test, the officer looks for six “cues” total, three in each eye: (1) lack of smooth pursuit, (2) distinct and sustained nystagmus at maximum deviation, and (3) onset of nystagmus prior to 45 degrees.

Healthcare professionals, including neurologists, neuro-ophthalmologists, and ophthalmologists, contend that a more detailed analysis of eye movements is necessary to understand the physiology of the eyes, and none of them have recommended a cursory roadside test performed in darkness with a flashlight by a police officer who has taken a 3-day course.

Studies conducted by recognized scholars in the area of optical dysfunction, all of whom have received more training than the 3-day weekend of lectures that is received by police officers, use video-oculography (VOG) to evaluate the occurrence and type of nystagmus.  In addition, these professionals contend that videos of the examination require review to confirm the results in certain cases. The use of VOG and nystagometers to record and preserve recordings of eye movements is an improvement from the earlier technology of electronystagmography, which relied on digital video cameras to record positive and negative discharges of the eye (i.e., corneal retinal potential). VOG technology uses infrared cameras to detect the original position of the eye and any changes in its position. As the computer cannot determine eye movements by itself, the examination requires a physician/clinician who is an expert in the anatomy and physiology of ocular motility.

The NHTSA HGN test has been criticized harshly in the medical literature, including the leading ophthalmological textbook, which states: “Unfortunately, the fact that alcohol can produce horizontal gaze-evoked nystagmus has led to a “roadside sobriety” test conducted by law enforcement officers.

Nystagmus as an indicator of alcohol intoxication is fraught with extraordinary pitfalls: many normal individuals have physiologic end-point nystagmus; small doses of tranquilizers that wouldn’t interfere with driving ability can produce nystagmus; nystagmus may be congenital or consequent  to structural  neurologic disease; and often a sophisticated neuro-ophthalmologist or oculographer is required to determine whether nystagmus is pathologic. It seems unreasonable that such judgments should be the domain of cursorily trained law officers, no matter how intelligent, perceptive, and well-meaning they might be. As noted, meticulous history-taking and drug-screening blood studies are often essential in evaluating patients with nystagmus.” (William Tasman, et. Al.. (2007). Duane’s Ophthalmology. Lippincott Williams & Wilkins. Vol. 2, Chapter 11, Page 20.)

The NHTSA test procedures take a very simplified (and ignorant) view of nystagmus, indicating that any time nystagmus is present, it is likely to be the result of intoxication.   In comparison, the use of sophisticated equipment by medical professionals to evaluate and record eye movements has led to the discovery of 49 types of nystagmus and their causes.  To conduct precise evaluations, ophthalmologists and other medical professionals use infrared technology, magnetic search coils, and/or specialized video recording systems.  It is also worth noting that ocular movements are highly complex, often involving the possibility of combinations of different kinds of nystagmus.  Recordings of the examinations therefore help provide accurate and reproducible results. (Hilla Levo, Nystagmus Measured with Video-Oculography: Methodological Aspects and Normative Data, (Journal of otolaryngology head and neck surgery) ORL 2004; 66:101-104; Jennifer Y. Luu, et. Al., Sensitivity to synchronicity of biological motion in normal and amblyopic vision, In Press, Accepted Manuscript, Vision Research, Available online 6 March 2013: access March 6, 2013 at Noon; William Tasman, et. Al.. (2007). Duane’s Ophthalmology. Lippincott Williams & Wilkins. Vol. 2, Chapter 11, Page 20.)

It is indisputable that highly qualified physicians and scholars require specialized equipment including nystagometers, VOG, and infrared science to properly conduct nystagmus tests and to record eye movements for later review to ensure accuracy. It is unreasonable to think that a police officer with no medical background and only a 3-day course on field sobriety tests can accomplish the same task.  Law enforcement officers lack any specialized equipment, administer tests on the side of the road with only a flashlight as a light source, and report and testify in court that the results are scientifically valid to obtain a conviction of a citizen.

In 2001, researchers determined that the HGN test was improperly conducted by more than 95% of police officers who used it as a criterion for placing drivers under arrest. (JL Booker End Position Nystagmus as an indicator of Ethanol Intoxication.  Science & Justice 2001 41: 113-116.)

Researchers paid by the Department of Transportation subdivision of NHTSA admit that these tests are only accurate when performed in the exact manner indicated by the NHTSA manual. Assuming that the test can be conducted accurately, the discovery that it is conducted improperly provides more evidence of its unreliability.

The One-Leg Stand Test – Designed For Failure

According to NHTSA:

“In the One-Leg Stand test, the suspect is instructed to stand with one foot approximately six inches off the ground, stare at the raised foot and count aloud by thousands (One thousand-one, one thousand-two, etc.) until told to put the foot down. The officer times the subject for 30 seconds. The officer looks for four indicators of impairment, including (1) swaying while balancing, (2) using arms to balance, (3) hopping to maintain balance, and (4) putting the foot down.

NHTSA research indicates that 83 percent of individuals who exhibit two or more such indicators in the performance of the test will have a Blood Alcohol Concentration of 0.08 of greater.

In general, a person’s brain has three primary mechanisms that help maintain balance. First, the visual perception of the horizon supports orientation. Second, when standing, the brain receives feedback from the feeling of the location of the feet to determine a person’s center of gravity (i.e., proprioception), and the brain sends impulses through the muscles and nerves to make adjustments that maintain balance. Third, the vestibular or “inner ear” mechanism also aids in maintaining balance. Individuals normally use all three mechanisms at the same time to maintain balance rather than trying to balance with only one of three functional mechanisms.

Having an individual raise one leg off the ground removes his or her proprioceptive ability. As the individual is told to stare at his/her foot, this action further eliminates the horizontal perspective required for orientation and balance. As a consequence, the individual is asked to use only one of three regular faculties, thereby losing the synergistic effect of all three mechanisms.

The Walk and Turn Test – Unnatural Body Movements

The NHTSA instructions:

“Keep your left foot on the line, use an imaginary line if there is no line on the ground to use, put your right foot directly in front of your left foot with heel touching toe.  Stand in that position and do not move until told to do so. Do you understand? When told to begin, take nine steps heel touching toe, when you reach your ninth step, leave your front foot on the line and turn making a number of small steps, and then come back nine steps heel to toe.  While you are doing this, keep your hands at your side, watch your feet at all times, count aloud and don’t stop until you have finished the test.

Signs of Impairment the officer notes are: (a) The Subject starts too soon.  (b)  Cannot maintain balance during instructions with one foot directly in front of the other standing heel to toe. (c) During the walking phase, the subject misses heel to toe by ½” or more. (d) Uses arms for balance by the raising of an arm for balance by 6″ or more. (e) Steps off line. (f)  Turns incorrectly. (g)  Takes the wrong number of steps.

This test requires that a person have a good center of gravity as stability and balance are required to complete the test successfully.    A person’s center of gravity is dependent on their height and the lateral spacing of his/her feet when standing.  For example, the feet of a person 70 inches in height are usually placed 4 inches apart. For taller individuals, more space is needed to achieve the same balance.  Studies have shown that walking (motion) is considered a prime suspect in causing falls or loss of balance.

In short, this test does not evaluate impairment due to alcohol use, and the scientific basis for this test has never been explained in any NHTSA publications.

Field Sobriety Tests Do Not Equate to Impairment or BAC

Basic pharmacology has shown that Standardized Field Sobriety Tests are unreliable in certain individuals. (Marc Schuckit (2011). Chapter 23. Ethanol and Methanol., Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 12e. Retrieved October 22, 2012 from; James Roberts, et. Al. Alcohol levels do not accurately predict physical or mental impairment in ethanol-tolerant subjects: relevance to emergency medicine and dram shop laws.  J Med Toxicol. 2010 Dec; 6(4): 438-42.)

The scientific literature and case reports show that certain individuals can have Blood Alcohol Concentrations ranging from the legal limit of 0.08 g/ml to as high as 0.500 g/ml while showing no signs whatsoever of mental or physical impairment. (James Roberts, et. Al. Alcohol levels do not accurately predict physical or mental impairment in ethanol-tolerant subjects: relevance to emergency medicine and dram shop laws.  J Med Toxicol. 2010 Dec; 6(4): 438-42.)

Thus, some persons can have a BAC more than six times the legal limit and still show no signs of impairment, intoxication, or consumption of alcohol. This fact must be addressed as part of any SFST study, otherwise police officers may allow drivers with high BACs to return to the road. Furthermore, NHTSA instructions do not include any evaluation to rule out any other causes of  perceived impairment other than intoxication observed by officers, such as vertigo, neurological pathology, medical issues, and/or a psychiatric disorder.

Independent Evidence of the Inaccuracy of SFST

Spurgeon Cole and Ronald H. Nowaczyk of Clemson University in Clemson, South Carolina conducted a well-designed blind experiment to test the effectiveness of Standardized Field Sobriety Tests in identifying those who are too impaired to drive and/or with Blood Alcohol Concentrations over the legal limit. Fourteen police officers of varying experience were asked to rate the performance of twenty-one individuals who underwent a battery of SFSTs and other tests of normal ability. Some officers had 17 years of experience in DUI enforcement, and all officers were certified by the state academy of police officers; they were field officers who were fully trained and in active duty. The individuals tested ranged in age from 21 and 55 years, were not overweight, and had no disabilities.  The officers were randomly assigned to conditions in which they evaluated a SFSTs or normal abilities test.  All subjects were completely sober, with no drugs or alcohol in their systems.

They performed the walk and turn test, the one-leg stand test, as well as other tests. The HGN test was not included because it required officers to monitor subjects’ eye movements, which would have been difficult to videotape in a controlled fashion. NHTSA procedures were implemented, and subjects were given an opportunity to have the instructions re-read.

The officers reviewed video of 21 subjects performing the tests and were asked to give a “yes” or “no” response to whether individuals were too impaired to drive.  Regardless of the fact that no subjects were intoxicated, the officers believed that half of the subjects were too impaired to drive.  In a real-world situation, therefore, SFSTs may be just as likely to lead to the arrest of sober individuals as those who are too impaired to drive.  (Spurgeon Cole., Field sobriety tests: are they designed for failure? Percept Mot Skills. 1994 Aug; 79 (1 Pt) : 99-104.)


In my opinion, the fact that the National Highway Safety Transportation Administration continues to promote the use of Standardized Field Sobriety Tests (SFST) is unethical and fraudulent.  The SFSTs constitute a useless exercise for both the officer and the individual being investigated,  as they are based on ideas that are scientifically unreliable and incorrect.  The basic research on which these tests were designed is full of error, and those who conduct the tests are not qualified to do so, making SFSTs invalid and unreliable.

SFSTs are no better than guessing as proven by Cole and Nowaczyk’s study.   There is no question that these tests need to be abolished.   Many persons have been wrongfully convicted in court based on a police officer’s testimony regarding these unreliable tests.

The observations of an officer of a driver’s performance of these SFSTs are admitted in court by judges as so-called “evidence” in cases where individuals are facing punishments as serious as life in prison for DUI, and are used to prove the person guilty “beyond a reasonable doubt…”

The real fraud is that Standardized Field Sobriety Tests carry an aura of credibility because of the National Highway Traffic Safety Administration’s seal of approval.   These tests tell us nothing about whether a driver is truly impaired, and only provide the officer with the opportunity to say that the driver failed the tests.  For this reason, a driver should NEVER agree to perform the tests