Elements of Standardized Field Sobriety Tests

Standardized Field Sobriety Tests (SFST) are psychophysical tests. A test is an “objective” and “standardized” measure of a sample of behavior, focusing on three elements:

1) Objectivity: Aspects of a test are based on objective criteria. For example, the scoring or the interpretation of the score. Also, it is not influenced by the subjective opinion of examiner.

2) Standardization: There is uniformity of procedure in the administration, scoring and interpretation of the test and results.

3) Behavior Sample: A representative sample of a person’s behavior from which one can draw inferences and hypotheses.

A test is not a psychological X-ray, nor does it necessarily reveal hidden conflicts and forbidden wishes.

Psychological Tests

Psychological tests must meet three criteria: (1) Reliability, (2) Standardization, and (3) Validity. Tests are used by a variety of professionals, including psychologists, special-education teachers, guidance counselors, psychiatrists, speech therapists, nurses and engineers.

Psychophysical tests should require evaluation of the subject’s appearance and condition, ability to follow instructions, as well as balance and coordination. These types of tests are called Divided Attention Tests, for they require the subject to concentrate on more than one thing at a time, dividing the subject’s attention between mental and physical tasks.


Studies have shown that a person who is under the influence of an alcoholic beverage may be able to perform one of these tasks but rarely both. If under the influence of an alcoholic beverage, people are likely to make certain predictable errors while attempting these tasks. Since the mid 1970’s, the National Highway Traffic Safety Administration (NHTSA), with the cooperation and assistance of the law enforcement community, has conducted research that resulted in the development of a battery of three standardized field sobriety tests: Horizontal Gaze Nystagmus, Walk and Turn and the One Leg Stand to assist police officers in detecting impaired drivers.

Standardized Field Sobriety Test History

The program, which was previously termed the Improved Sobriety Testing, was validated in laboratory and field studies conducted by the Southern California Research Institute. These tests were initially developed by the Los Angeles Police Department and the methodology of conducting these tests is included in the NHTSA course “DWI Detection and Standardized Field Sobriety Testing.”

In 1986, the Advisory Committee on Highway Safety of the International Association of Chiefs of Police (IACP) passed a resolution which recommended that law enforcement agencies adopt and implement the field sobriety testing program developed by NHTSA. As the program grew, it became apparent that in order to insure continued success, nationally accepted standards should be established. Standardization that established criteria for the selection and training of SFST practitioners would help insure the continued high level of success of the SFST program. In 1992, the IACP Highway Safety Committee recommended the development of this system of nationally accepted standards.


In April of 1992, the IACP and NHTSA sponsored a meeting at the headquarters of IACP in Arlington, Virginia. Persons invited to this meeting included SFST instructors from several states, curriculum specialists and training administrators. The participants met in working groups to reach a consensus concerning the many issues relating to the SFST program and to develop recommended minimum standards to the IACP Advisory Committee on Highway Safety. The standards were drafted and presented to the committee for their review at the mid-year meeting in June 1992.

National Standards

The Advisory Committee on Highway Safety by resolution adopted the National Standards for the SFST Program and voting membership of the IACP subsequently approved the Standards. In order to maintain the credibility and integrity of the program, agencies that use a training program other than that which is currently approved by the IACP must have the alternative curriculum approved by the IACP Advisory Committee on Highway Safety as meeting the required learning objectives. This is supported by the National Highway Traffic Safety Administration.

Becoming Certified

Presently, SFST Training for Police officers (and the few DUI Defense Attorneys, including Attorney Ruane, who have been taught the regimen) must be 16 hours in length and include at least two controlled drinking sessions utilizing volunteer drinkers. This is in accordance with section 1.2 of the Standards for Training in Standardized Field Sobriety Testing. In section 1.4, in order to satisfactorily complete the classroom portion of the training, SFST candidates must complete the IACP-approved final examination with a score of not less than eighty percent. Candidates scoring less than 80% on the final may be re-tested one time under the supervision of a SFST instructor.


The retest shall be completed not less than 15 days and not more than 30 days following the completion of the classroom training, and the examination used shall not have been administered to the candidate previously. If the candidate does not achieve a passing score on reexamination, the candidate must retake the classroom portion of the training and pass the final examination.

The U.S. DOT requires 35 practice tests within a six month period, but local and State Police have varying requirements based on their own department’s criteria. A refusal of a chemical test cannot be considered a practice test, as a blood alcohol reading must corroborate the evaluation of the suspect. The officer is trained to conduct the HGN test last during his practice test period and not to formulate an opinion based on the results or use it for probable cause to arrest. They are told not to document the test due to this.

At no time may a person that is tested be used more than once on a practice test. As a result of this it is necessary to review the documentation of the practice tests in order to determine if the practitioner was properly recommended for certification.

Giving the Tests

After probable cause is determined, an officer will most often attempt to recover more evidence that the driver is under the influence of drugs or alcohol and an officer may ask a person to perform Standardized Field Sobriety Tests. In every state you do not have to take field sobriety tests, but in each state the law is different regarding whether or not you have to consent to a blood breath or urine test. Standardized Field Sobriety Tests, usually conducted on the side of the road, do nothing to prove your sobriety, and oftentimes can hurt your defense.

The officer cannot force you to do these tests, so politely decline. However, in Connecticut, while you do not have to take a blood, breath or urine test, a refusal will trigger a longer DMV administrative suspension. If an officer tells you he will let you go if you take them, you should still decline. They can only add to the probable cause for your arrest.

Types of Tests

Generally there are three “tests” which are administered on scene. These tests are the Walk and Turn, the One Leg Stand, and the Horizontal Gaze Nystagmus. The three tests are most often used together and have shown 93% accuracy in Colorado in 1995, 95% accuracy in Florida in 1997 and 91% accuracy in San Diego in 1998, however, there are many scientists who refute the validity of these tests. The Horizontal Gaze Nystagmus is still the most accurate of the three and is said to “provide valid indications to support arrest decisions at 0.08 and strongly suggests that it can provide valid indication of 0.04 and above.”

Combined Accuracy

When the Horizontal Gaze combines with the Walk and Turn it has 80% accuracy, but when tested with all three the higher degree of accuracy increases. These three tests, however, have never been subject to peer review. (Peer review is the process in which scientists publish their methods and results to other persons in their field to allow for critical analysis of the data and results.)

Field Testing will most often occur on the side of the road after one has been suspected of being under the influence. The results of the test will help the officer to support evidence if they find you to be under the influence of drugs or alcohol.

Refusing the Tests

You can simply tell the officer that you do not wish to take the tests. Remember to be polite with the officer because it can only help you later but refraining from field tests is your right. They are not required and in most cases will only hinder you when it comes time for court. Conditions for field-testing are often not ideal with uneven ground; poor lighting, weather and even improper attire and footwear could hinder accurate results.

Horizontal Gaze Nystagmus

The suspect must get instructed to look straight ahead, keeping the head still while following and focusing on the stimulus with the eyes until told to stop. The stimulus must remain twelve to fifteen inches in front of the suspect’s eyes for ease of focus. The officer should receive an acknowledgement from the suspect that the stimulus exists at a comfortable distance from the suspect’s eyes and to document this confirmation.

Even though this test is not a vision test, per se, eyeglasses are to be removed in order for the officer to make a more accurate determination of the final total points. If the suspect can not see the stimulus after removing the eyeglasses, they must be allowed to perform it with them on. According to the manual, hard contact lenses are to be removed so as to avoid dislodging when the eyes are out at maximum deviation or to prevent damage to the eyes.

When Not to Test

A person with a glass eye or only vision in one eye can not be given this test for evaluation of just one eye and then a subsequent doubling of the score, assuming that the other eye will render the same results, is both erroneous and improper. If the suspect has what is known as the lazy eye condition, the officer is trained to test one eye while the other eye is covered by the suspects’ hand, then to switch same.

A person who is color blind is not validated for this test as they will probably have a pathological Nystagmus which is normal and natural for that condition. This can be caused by some type of neurological disorder, brain damage, epilepsy or pathological disorder which the suspect is born with or of unknown etiology. A large disparity between the right and left eye can clue the officer into this problem. At an accident scene, if the suspect sustains a concussion, this may bring on a pathological Nystagmus thereby invalidating this test.

Administrative Procedures

Although very few test conditions affect gaze Nystagmus, there exist certain administrative procedures to follow. As previously mentioned, the stimulus must get placed twelve to fifteen inches in front of the suspect’s eyes. The stimulus should get held above eye level, so that the eyes are wide open and looking directly at it. Due to narrowness of certain individuals’ eyes it becomes more difficult to make a fair evaluation of the Nystagmus unless the eyes are wide open.

If the officer believes that the Nystagmus might exist, it can not get scored, as the benefit of the doubt must go to the person tested. The officer also gets trained to administer this test with the suspect looking into a quiet background, facing away from police cruisers and oncoming traffic. This avoids the probability of evaluating an induced condition known as optokinetic Nystagmus, which develops when a person focuses on several objects at one time or on objects moving away.

Optokinetic Nystagmus

This optokinetic Nystagmus is a defense mechanism of the body in order to keep the eyes from tiring. There are numerous visual or other distractions that may also impede this test. Certain environmental factors such as wind and dust may interfere with the performance of the Nystagmus test. When administered alone, Horizontal Gaze Nystagmus is considered to be 77% accurate by the law enforcement community.

First Clue: Lack of Smooth Pursuit

As explained earlier, Nystagmus is the involuntary jerking of the eyes. With alcohol intoxication, three clues will be sought after, the first of which is smooth pursuit. The officer must look for the suspect’s inability to pursue a stimulus smoothly moving horizontally while focusing on that. If the suspect moves his head to the side at any time, the score may be invalid regardless of which clue the officer is looking for. An example of smooth pursuit is a marble rolling across a smooth pane of glass: this would be a very smooth pursuit.

If the suspect is under the influence, the eyes will bounce or jerk in similar fashion, as if that same marble was rolled across a piece of sandpaper. The officer must check the left eye first by moving the object to the officer’s right. The object must get moved smoothly in order to comfortably bring the suspect’s eye as far to the side as it can go. Any choppy or shaky hand movements or movement that is too fast by the officer may induce a Nystagmus in the suspect’s eyes and invalidate the test.

The officer must make two or more passes in front of the eye to know that a Nystagmus exists. If this clue is scored as Nystagmus the suspect is assessed one point. However, if the suspect has this clue emanating in one eye, this does not mean it also exists in the other eye.

Second Clue: Distinct Jerkiness at Maximum Deviation

After the officer has checked the first eye for the smooth pursuit clue, the same eye must get checked for distinct jerkiness at maximum deviation. This is accomplished by simply moving the object to the side until the eye has gone as far to the side as possible. At maximum deviation, no sclera or “white” will be showing in the corner of the eyeball. The officer must hold the eyeball at that position for two or three seconds and attempt to discern distinct eyeball jerkiness.

If the officer can not make this distinction from a slight Nystagmus, the benefit of the doubt must go to the suspect. The officer may make the mistake of not bringing the eyes out to side as far as they can go or too rapidly returning the stimulus and incorrectly score this part of the test. During the test, a certain degree of uncomfortableness happens, causing a slight twitching of the eyes at maximum deviation and if the officer returns the stimulus too quickly, the natural Nystagmus may get mistaken for that caused by intoxication.

Final Clue: Angle of Onset

Although the most difficult to evaluate, the angle of onset is perhaps the greatest indicator of the presence of the other clues. This correlation, however, does not work conversely. The presence of either of the first two clues does not guarantee that the third clue will be present.

The person must follow the stimulus until they look down a 45-degree diagonal. In order to estimate the 45-degree angle, the officer must place the stimulus halfway between the suspect’s ear and nose on the side getting tested or just outside the shoulder area. The estimation of this angle is critical, since studies have shown that as the alcohol increases, the angle will decrease. This angle should not get used to estimate a specific amount of alcohol in the bloodstream.


To score this part of the test, the officer must move the object to a 45-degree angle so the eye matches this angle, looking for jerkiness in the movement. If Nystagmus gets observed, the stimulus stops and the officer must make note a continued jerkiness. But, if it does continue, the officer must observe whether there is still white showing in the corner of the eye and then the angle is noted as prior than 45-degrees. If no jerkiness happens, the stimulus must continue to move until the jerking occurs or the 45-degree angle gets reached.

Also, if no white of the eye is showing, the eye has either been taken too far to the right, which would indicate maximum deviation, or the person has unusual eyes that will not deviate very far to the side. The criterion of onset before 45-degrees only can get used if some white can still show at the outside of the eye, however, too often the officer incorrectly estimates the angle or scores this with no white showing in the corner of the eye or both.


This test is deemed the most reliable test in determining probable cause to believe someone is under the influence of an alcoholic beverage; however this obviously depends on whether the officer adheres to the proper administration and proper scoring of the test.

This test should not get administered if the suspect lies down but can get administered to them if they sit or stand.

Walk and Turn Field Test

Correct administration of this field test requires that it happen on a hard, dry, level, non-slip surface with sufficient room for the suspect to complete nine heel-to-toe steps. This test does in fact lose some validity when conducted in certain wind or weather conditions. The manual calls for a straight line, which must be clearly visible on the surface, however it is taught that the test can be performed parallel to the curb. Conditions must also cause a suspect to be in danger if they perform the test.

Some people should not take this test because even the average sober person would have difficulty with it. People more than sixty five years of age or over fifty pounds overweight or with any physical impairment that would affect their ability to balance should not take this test. The officer should take this into account when developing their probable cause for arrest.

Individuals wearing heels more than two inches high should have the opportunity to remove their shoes, as this may affect the subject’s ability to balance and subsequently hinder the validity of the results. Individuals who can not see out of one eye may also have trouble with this test because of poor depth perception and should not take this test as well.

Administering the Test

The Walk and Turn test is an objective test based upon certain predictable errors that a person under the influence will display, as well as scoring factors that will give the officer a basis for passing and failing other than a subjective opinion. In order to properly administer this test, it is important to understand what type of test this is. It is commonly referred to as a Divided Attention Test because it divides the suspect’s attention between mental and physical tasks. The physical tasks include balance and coordination while the mental tasks include comprehension of verbal instructions, the processing of information and the recall of memory. While a person may be able to perform one task, they may not be able to perform the other if under the influence of an alcoholic beverage.

Police Observation

While the suspect performs this test, the officer must observe the suspect from three away. Also, they must remain motionless. Causing distraction with excessive motion may cause the suspect to make errors. This causes the loss of validity of the test. Even a sober person may have difficulty under these particular conditions. The officer must give clear verbal instructions, only to supplement this with a demonstration of the test, and must receive affirmative confirmation of the suspect’s comprehension of the instructions.

Scoring the Test

This test gets scored in relation to eight scoring factors in two separate stages. When administered alone, the Walk-and-Turn test is considered to be 68% accurate. However, when combined with the Horizontal Gaze Nystagmus, the two are considered 80% accurate. The first stage of this test is called the Instruction Stage and will set the stage for the entire test. If the officer does not follow training and procedure perfectly during this stage, the test could be invalid. The officer must verbally explain to the suspect the heel to toe stance and then demonstrate it.

Officer Testing

The suspect must place their left foot on the line and their right foot on the line ahead of the left foot. This happens with the heel of right foot against toe of left foot. The absence of a visual demonstration can discredit the test.

The officer should make sure the right foot stays in front of the left foot to start. This maintains uniformity in testing. This also becomes important later in the test during the turning evaluation. If the suspect gets instructed or demonstrated improperly, it may affect the suspect during this part of the test. After accomplishing the starting position, the officer must inform the suspect to remain in that position until told to start walking.

Stage One

There are two ways that the officer can assess a point against the suspect’s performance. If the suspect cannot keep balance while listening to the instructions, a point gets scored. This item is only scored if the suspect does not maintain the heel to toe position throughout the instructions. The officer should remain conservative in their scoring. They should not score a point if the suspect sways. Also, they should not score a point if the suspect uses the arms to balance but maintains the starting position. A second scoring factor is known as starting too soon. This is given when the starts to walk before the officer instructs them to do so. This can only get scored if the officer specifically instructed the suspect not to start until told to begin.

Stage Two

The second stage of this test is known as the Walking Stage. The suspect gets informed again, that when told to start, they must take nine heel to toe steps. They also have to turn around, and take nine heel to toe steps back. The officer must demonstrate two or three heel to toe steps for the suspect. They also have to show how to turn. The foot must stay on the line and turn by taking a series of small steps. The officer then continues to instruct the suspect to keep their arms at their sides while walking. The suspect must watch their feet at all times. Also, the suspect has to count their steps aloud and not stop once they have begun. If the officer does not once again confirm the suspect’s understanding of the instructions, the test results may get invalidated.

Scoring the Walk and Turn

There are six scoring factors that can be observed in this stage. The first is if the suspect stops to regain balance once the test has started. The officer can not score this item if the suspect is merely walking too slowly. But, they can only score this if the suspect pauses for at least several seconds after one step. Once this occurs, the officer has the suspect begin from the point of difficulty instead of starting over. This test loses sensitivity if repeated several times. Another scoring factor is referred to as not touching heel to toe. If the suspect leaves a one half inch or more between the heel and toe or does not walk straight along the line they can only get assessed one point. This happens no matter how many times this occurred.

Instruction Stage

During the instruction stage, if the suspect sways or uses their arms for balance a point can not get scored. A point only gets scored if the suspect raises their arms more than six inches to maintain balance. If this is the normal position of the arms, as in some bodybuilders, the officer must take that into account. They should be conservative in their scoring. The benefit of the doubt must be given to the suspect.

Loss of Balance

The next way a suspect can get a point is if they lose balance while turning. This item can only get scored if the suspect removes both feet from the line while turning. Or, if they do not take several small steps, and pivots in one movement. The officer must have demonstrated and articulated this movement properly in order to get scored.

Incorrect Amount of Steps

Finally, the last scoring factor is if the suspect takes the incorrect amount of steps. This item gets scored only once, even if an incorrect amount of steps gets taken in either direction. The suspect must look down at their feet while performing this stage of the test. Also, they must count their steps out loud. However, if they don’t adhere to these instructions, they can not get scored a point.

There are two ways that the suspect can receive a maximum of eight points on this test. The first occurs if the suspect steps off of the line three or more times. Also, the second happens if the suspect can simply not do the test. If the suspect receives at least two total points on this test, this is enough for a DUI charge .

One Leg Stand Field Test

In order to accurately administer this test, the officer must move the suspect to a hard, dry, level, non-slippery surface. Conditions must be such that the suspect would be in no danger if he or she were to fall. Certain wind or weather conditions obviously may interfere with and affect the validity of this test. This test should not happen for people who are more than sixty-five years of age. It also should’t happen for those more than fifty pounds overweight. Finally, those with physical impairments that interfere with balance should not take the test.

Individuals wearing heels more than two inches high should have the opportunity to remove their shoes. These shoes may diminish the reliability of the results. The officer gets trained not to give this test if the lighting is not right to perform it. In total darkness, even the average, sober person may have difficulty with this test. This comes from lack of visual frame of reference that would otherwise be provided with proper lighting.

As with the Walk and Turn Test, the officer should observe the suspect from at least three feet away. They should remain as motionless as possible so that there are no distractions.

Instruction Stage

In the administration of this test, there also exist two separate stages involved. The first stage is also called the “Instruction” Stage. The test gets initiated by giving verbal instructions, followed by a demonstration. The officer must advise the suspect to stand with their heels together and arms down at their sides. They should not start the test until told to do so. As before, the officer must receive affirmative confirmation that the suspect understood the instructions and then document this acknowledgment. There are no scoring opportunities until the next stage of the test, the Balance and Counting Stage. This happens unless the suspect can not even perform the test, which would of course get scored. This would give the suspect a maximum score of four points. Also, it would necessitate explanation on the part of the officer.

Balance and Counting Stage

At the start of the “Balance and Counting” Stage, the officer must explain the test requirements. They do this by instructing the suspect to stand on one leg. The suspect can choose which leg to stand on. They must hold the other foot in front about six inches from the ground. While standing, the suspect must keep their arms at their sides. They can only look at the extended foot, and must refrain from swaying or hopping. Finally, they have to count out loud for 30 seconds, counting each second as “one-one thousand”. The officer then demonstrates all of the above mentioned instructions. After that, the test can begin.

Scoring the One Leg Stand:

A suspect may get scored a point for the following reasons:


Suspect sways while balancing. The officer gets trained not to be too critical in this scoring. Because the suspect is human, some sway is a natural reaction. The swaying that can be scored is a marked sway. For example, a back-and-forth motion while the suspect maintains the position.


The suspect uses the arms for balance, raising six or more inches from the side of the body. The officer must take into account the natural position of the arms, as in the case with body builders. For some, the natural position of the arms may be farther than six inches. If the suspect puts their foot down, regardless of how many times, they can only get one point. The suspect should continue from the point of difficulty. This test may lose sensitivity if repeated several times.

The suspect should have instruction to keep watching their raised foot and to count out loud. But, if they do not follow either of these instructions, they don’t lose any points. If the suspect counts too slowly, the officer must stop the test after thirty seconds have elapsed. This may affect the scoring and validity of the test. The officer should time thirty seconds of total test time. If the suspect counts too fast the officer needs to slow them down.


The last scoring factor in this test is whether or not a suspect hops on one foot. This is scored only if they resort to hopping on the anchor foot in order to maintain balance. It should not get scored if the suspect has difficulty by moving the anchor foot back and forth. The officer should distinguish this as part of their training. Also, they should allow the suspect this benefit.

Maximum Score

The suspect can receive a maximum score on this test in two ways. The first would happen if the suspect puts their foot down three or more times. The second is if the suspect is too intoxicated to perform the test. However, the officer must articulate why they felt the defendant could not perform the test. The degree of reliability of this test is 65% if instructed and scored properly.

For arrest report and courtroom testimony, it is not enough to report the suspect’s “score” on the three tests. The numeric scores are only important to the police officer in the field to determine probable cause. However, merely a score is insufficient to secure a conviction. It must get accompanied by more descriptive evidence. The officer must describe in detail how the suspect performed. Also, the manual provided to the officer has a standard note-taking guide. This should assist the officer and prove the case.

Sobriety Tests Not Yet Validated

Counting Backwards

This divided attention test requires a person to count out loud a set of numbers in reverse order. For example, the person gets instructed to count starting with 56 and ending with 28. This divides the person’s attention because they have to remember what number to start with. Then, they have to count backwards correctly, and remember what number to stop on. Anything other than 100% perfection will get viewed as a sign of intoxication.


This test requires a person to recite a portion of the alphabet. For example, the person gets instructed to start with a specific letter, D, and stop at a specific letter, T. This divides the person’s attention because they have to remember the specific letter to start with. Also, they must say the letters in sequence, and remember the letter to stop with. Anything less than 100% perfection will get viewed as a sign of intoxication.

Finger Count

This test required a person to touch the tip of each finger in succession to the tip of their thumb, up and back, while counting 1, 2, 3, 4, .. 4, 3, 2, 1. They must touch fingertips while not counting out of order. Anything less then 100% perfection will get viewed as a sign of intoxication.

Stationary Balance (i.e. Rhomberg)

This test requires a person to stand with heels and toes touching. They have to lean their head back to look up at the sky or ceiling. Also, they must hold their arms out to the side and estimate 30 seconds. The officer is looking for any unnatural sway. I have had officers testify that anything more than ½ inch to 1 inch from center is too much sway. They say this must result from intoxication. Also, if you do not estimate to 30 seconds, they consider this a sign of intoxication.