Field sobriety tests ("FSTs") are a series of physical and mental exercises that police administer in DUI investigations. Performance on the tests is one of the factors police, prosecutors and courts consider in gauging whether a driver is under the influence of alcohol or drugs.
Poor performance on these exercises (as well as difficulty following the officer's instructions) is thought to be a sign of mental and/or physical impairment stemming from alcohol or drug consumption.
Law enforcement officials rely a great deal on FST exercises in deciding whether to arrest DUI suspects. The same is true of district attorneys in filing DUI charges and making their cases in court.
Despite their widespread use, these tests are notoriously flawed and unreliable.
In fact, even the most "reliable" field sobriety tests are only between 65-77% accurate at detecting whether or not a driver is intoxicated.1
This means that, on average, one out of every three or four people who get arrested for a DUI based on failing the FSTs are not under the influence.
The following is a brief summary about DUI field sobriety testing. Topics that we address include:
1. The National Highway Traffic Safety Administration's Role with Respect to DUI Field Sobriety Testing
If, after reading this article, you would like more information, we invite you to contact us at Shouse Law Group to schedule a free consultation with a member of our firm.
To receive more in-depth analyses of specific field sobriety tests or DUIs in general, you may also find it helpful to visit our pages on the Horizontal Gaze Nystagmus Field Sobriety Test, The Walk-and-Turn Field Sobriety Test, The One-Leg-Stand Field Sobriety Test, The Hand-Pat Field Sobriety Test, The Finger-to-Nose Field Sobriety Test, The Rhomberg Balance Field Sobriety Test, The Finger Count Field Sobriety Test, Driving Under the Influence, and Fighting DUI Charges.
1. The National Highway Traffic Safety Administration's Role with Respect to DUI Field Sobriety Testing
The National Highway Transportation Safety Administration (NHTSA) is a federal agency that issues police protocols for DUI field sobriety testing.2
NHTSA has concluded that there are three FSTs that, when administered correctly, are reliable enough to gauge whether an individual is too intoxicated to drive safely.3
NHTSA has supported this position by pointing to several scientific studies establishing a significant correlation between poor performance on the three tests and DUI impairment.4
Consequently, these three tests are referred to as "standardized" field sobriety tests.5
NHTSA has created highly detailed procedures for officers to follow when overseeing these standardized tests, as well as specific clues to look for in scoring the tests.
However, as noted by our California DUI defense lawyers in subsection five, these "standardized" tests (along with a lengthy list of non-standardized tests) may be a critical source of deception and error in DUI investigations.
As noted earlier, NHTSA has approved three "standardized" field sobriety tests to aid law enforcement officials during their DUI investigations. These three standardized field sobriety tests are:
- the horizontal gaze nystagmus test (HGN),
- the walk and turn test, and
- the one-leg stand test6
While these tests are further discussed below in this subsection, please visit out pages on the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test to receive a more thorough evaluation of each of these standardized field sobriety tests.
Several different kinds of nystagmus exist, only some of them influenced by alcohol. However, the test given at roadside in a DUI investigation is a test of "horizontal gaze nystagmus."7
Horizontal gaze nystagmus refers to an involuntary jerking of the eyes as the eyes gaze toward the side. In addition to being involuntary, the person experiencing the nystagmus is unaware of its occurrence.8
During the administration of the horizontal gaze nystagmus field sobriety test, the officer instructs the suspect to follow (with his eyes) a stimulus to the left and to the right.
The officer notes the angle at which the pupil starts to exhibit "nystagmus" (an involuntary jerking of the eye).9
An early onset of nystagmus (at or before a 45-degree angle) is a clue associated with a high blood alcohol concentration.
According to the National Highway Transportation Safety Administration (NHTSA), studies have revealed the HGN Test to be 77% reliable in determining whether a driver has a blood alcohol concentration above .10.10
The walk and turn test is a "divided attention" standardized field sobriety test.11 A divided attention test essentially involves splitting the attention of a suspected DUI driver between mental and physical tasks.12
The walk and turn test has the suspect listen to, follow and remember instructions while performing various physical movements.13
The walk and turn test is also sometimes referred to as the nine-step test, nine step walk turn, DUI straight line test, or DUI walk the line test.
During the walk and turn test, the suspect is ordered to:
- Take nine heel-to-toe steps on a real or imaginary line,
- Pivot around, and
- Take nine heel-to-toe steps back,14
While the officer observes the individual, he/she watches for eight clues that may indicate impairment. These clues include whether or not the suspect:
- keeps his or her balance during instructions,
- starts too soon,
- stops while walking,
- touches heel-to-toe,
- steps off line,
- uses arms to balance,
- performs improper turn or turns incorrectly, or
- takes an incorrect amount of steps.15
According to NHTSA, there is a 68% chance that a person who displays two or more of the above-mentioned clues has a blood alcohol concentration above .10.16
The one-leg-stand DUI field sobriety test is the second "divided attention" test among the three standardized field sobriety tests.17 During the one-leg-stand DUI field sobriety test, the officer instructs the suspect to:
- raise his/her foot about six inches off the ground,
- hold still in that position,
- count from 1001 - 1030, and
- look down at his/her foot.18
While the officer observes the individual, he/she watches for four clues that may indicate impairment. These clues include whether or not the suspect:
- Uses his/her arms to balance
- Hops, and/or
- Puts his/her foot down19
According to NHTSA, there is a 65% chance that a person who displays two or more of the above-mentioned four clues has a blood alcohol concentration above .10.20
In addition to the three standardized field sobriety tests explained above (i.e. horizontal gaze nystagmus test, walk and turn test, and one leg stand test), there are a number of other field sobriety tests that officers routinely use to aid in their DUI investigations.
The problem is that there are no studies that demonstrate the correlation between these "non-standardized" field sobriety tests and DUI impairment.
What is perhaps even more significant is the fact that the procedural administration of the test may vary a great deal from one police officer to the next.
Hence, when taking into account not only the inherent defects of the tests themselves, but also their random administration by law enforcement officials, the legitimacy and/or accuracy of these non-standardized field sobriety tests is all the more questionable.
A list of several popular non-standardized drunk driving FSTs include (but are not limited to):
During the administration of the hand-pat field sobriety test, the DUI suspect is to:
- Place one hand extended, palm up, out in front of him/her. The other hand should be placed on top of the first, with the palm facing down. The top hand should then begin to pat the bottom hand.
- The top hand should rotate 180 degrees, alternating between the back of the hand and the palm of the hand. The bottom hand remains stationary.
- The DUI suspect should then count out loud, "ONE, TWO, ONE, TWO, ONE, TWO, etc.," in relation to each pat.21
Law enforcement officials normally keep in mind the following four factors when administering the test and subsequently determining whether or not a suspect is impaired:
- Ability to follow instructions,
- Ability to count correctly,
- Rotation and sequence of the hand patting,
- When the subject starts and stops the test.22
During the finger-to-nose field sobriety test, the DUI suspect is required to:
- Bring the tip of the index finger up to touch the tip of the nose while his/her eyes are closed and his/her head is tilted slightly back (standing in a manner identical to that required for the Romberg Balance Field Sobriety Test).
- The DUI suspect is to attempt this six (6) times, three (3) with each hand. The officer should instruct the subject as to which hand to use on each attempt.23
Police officers usually consider the following seven factors in determining whether or not a subject is impaired during the administration of the finger-to-nose test.
- The subject's ability to follow instructions.
- The amount and direction in which the subject sways.
- Eyelid tremors and body/leg tremors.
- Muscle tone
- Any statements or unusual sounds made by the when performing the test.
- The subject's depth perception
- Whether the subject touches his/her index finger on his/her face.24
The Rhomberg balance field sobriety test evaluates the DUI suspect's internal clock. During the administration of the Rhomberg balance test, the DUI suspect is to:
- Stand with his/her feet together
- Have his/her head tilted slightly back
- Have his/her eyes closed
- Estimate the passage of 30 seconds
- When the DUI suspect believes that 30 seconds has passed, he/she should tilt his/her head forward, open his/her eyes, and say "stop."25
During the administration of the Rhomberg balance test, law enforcement officials normally keep in mind the following six factors when gauging whether or not a suspect is impaired.
- The amount and direction in which the suspect sways
- The suspect's estimated passage of 30 seconds
- Eyelid tremors and/or body/leg tremors
- Muscle tone (either more rigid or more flaccid than normal)
- Any statements or unusual sounds made by the subject when performing the test
- Suspect's overall ability to follow instructions.26
During the finger count FST, the officer instructs the DUI suspect to:
- Put one hand in front of him/her with the extended palm facing upward.
- Have the top of the thumb then separately touch the tip of the index, middle, ring and little finger.
- Count out loud, "ONE, TWO, THREE, FOUR" in relation to each finger-thumb connection.
- Reverse the process, completing a total of three complete sets.27
During the administration of the finger count test, officers usually keep in mind the following five factors when determining whether or not a suspect is intoxicated and/or impaired.
- Ability to follow instructions
- Ability to count correctly
- Ability to touch each finger separately and in correct sequence
- When the subject starts and stops the test
- Performance of the correct number of sets.28
NHTSA requires that the three standardized field sobriety tests (walk and turn test, one-leg stand test and horizontal gaze nystagmus test) be performed under appropriate and safe test conditions.
Adverse conditions can make the tests unreasonably difficult to perform. Thus, police must make certain that suitable conditions be maintained; else the results of the tests may be invalidated.
There is no uniform set of procedures for police to follow when giving the non-standardized FSTs. But courts and juries will want to see that these tests as well be given under fair and reasonable conditions.
These relevant test conditions include, but are not limited to:
1) Surface Settings:
- Field sobriety tests should generally be conducted on a reasonably dry, hard, level, non-slippery surface, and under conditions in which the DUI suspect would not be in danger of falling.
- There should be sufficient room for the suspect to perform and/or complete the test.
- If these guidelines cannot be adhered to at the place where the suspect is stopped, then the law enforcement official should try to move the suspect to a better location.29
2) Light Settings:
- The officer should further make sure that adequate lighting exists during the administration of field sobriety tests. If the suspect cannot see the officer and the ground below fairly well, then the lighting may be determined inadequate.
- If the lighting is not adequate, then the officer should use a flashlight to illuminate the ground. In total darkness, several of the field sobriety tests (unsurprisingly) become extremely difficult for even the soberest of drivers to perform.30
3) Audial Settings:
- The officer should further make sure that a proper noise level exists during the instruction stage of the field sobriety tests. If the suspect cannot hear the officer give the instructions, then the audial settings should be determined inadequate.
- If any disruptive honking, sirens, or other noise disturbances exist, then the officer should take the suspect to a more suitable location.31
According to the national government's own studies, even the most reliable field sobriety test (the horizontal gaze nystagmus test) is only 77% accurate in determining whether a driver has a blood alcohol concentration above .10.32
This essentially means that at least roughly one out of four people who fail a field sobriety test are NOT intoxicated.
Significantly, this ratio is based on the assumption that the field sobriety tests are administered properly in accordance with NHTSA guidelines.
In reality, however, not only do the tests carry their own inherent flaws, but their administration by law enforcement officials, as pointed out by Senior DUI/DWI Field Sobriety Test Instructor Robert "Bob" LaPier, often fall short of NHTSA standards.
Clearly, the reliability of these field sobriety tests are in serious question. Any good DUI defense attorney should therefore be able to expose several weaknesses in the procedures/ administration of the field sobriety tests in a DMV hearing and/or in the courtroom.
Some of the general weaknesses ripe for attack by our California DUI defense lawyers and pertinent to most if not all field sobriety tests include:
1. Physical and/or mental impairments:
- If a suspect is over 60 years of age, sick/ill, has any back, foot, leg, inner ear problems, or even if the suspect is overweight by 50 or more pounds-these potential physical impairments, along with a countless list of others-may inaccurately skew the results towards failure.
- Alternatively, if a suspect had been particularly inclined to nervousness/intimidation during the testing, has any brain damage or suffers from any mental disabilities that would inhibit his ability to comprehend and/or follow instructions, then the test results would again be questionable.33
2. Officer movement:
- The officer is supposed to remain as motionless as possible during many of the field sobriety tests so as not to interfere with it. If an officer, however, decides to walk around or exhibit any other forms of distractive behavior during the testing, then the results may be deemed tainted.34
3. Unsuitable attire:
- If a suspect had been wearing heels, boots, dress shoes, gloves, tight leather pants or baggy/beltless jeans or any other type of clothing that may have inhibited his or her ability to effectively maneuver or perform the test, then the test results may be invalid.
4. Improper timing:
- Timing is critical in several field sobriety tests. If the officer does not time the test with a watch and/or in any way starts/ends the timing incorrectly, then the test results may not be accurate.
5. Unfair environmental conditions:
- Any results obtained from the administration of field sobriety tests by law enforcement may be deemed invalid if there is inclement weather, poor lighting, uneven surface conditions, and/or the distraction of traffic, lights, and/or spectators,
6. Non-Standardized Testing:
- Since there are no NHTSA approved procedures to aid officers in the administration of the lengthy list of non-standardized field sobriety tests, there potentially exists an even greater lack of sufficient objectivity in each officer's administration/determination of whether or not a particular suspect is drunk driving.
- Significantly, as acclaimed Ventura County DUI lawyer John Murray explains, "Unlike the "NHTSA 3", these remaining field sobriety tests have no uniform method of administration, nor any scientific data to support their reliability. As a result, I always aggressively attack the findings from these and any other non-standardized FST."35
7. Non-Alcohol Related Causes for Coordination Failures:
- The lack of proper physical coordination that police officers frequently monitor during the field testing process may in fact be due to causes other than alcohol. Some of these causes include seizure medications or being physically exhausted.
8. Incorrect/Vague Instructions:
- The investigating officer(s) should precisely inform the DUI suspect on how to successfully perform the various field sobriety tests. These precise instructions are necessary during any oral directives and/or visual demonstrations given by the officer. If the officer does not correctly instruct the suspect (either orally or visually) on how to properly conduct the test, then any subsequent test results may be all the more questionable.
Oftentimes, a DUI suspect wonders how to respond to a police officer requesting him/her to take a field sobriety test.
Unlike refusing a chemical test, declining to take a FST does not have any legal penalties in California. Politely declining the FST is therefore a valid option for you to take.
As noted by Senior DUI/DWI Field Sobriety Test Instructor Robert "Bob" LaPier,36 an officer has most likely already made his judgment and decision of arrest before requesting a field sobriety test.
In this context, field sobriety tests are generally "designed for failure,"37 enabling an officer to validate the stop and gather further evidence against you.
It is therefore generally recommended that one should always (politely) refuse taking any field sobriety test when requested by an officer.
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Our Nevada DUI law offices are located in Las Vegas and Reno.
If you have additional questions about DUI field sobriety tests, or you would like to discuss your case confidentially with one of our DUI defense attorneys, please don't hesitate to contact us at Shouse Law Group.
1 U.S. Department of Transportation "DWI Detection and Standardized Field Sobriety Testing" NHTSA Student Manual (February 2006): VII-3. If a suspect displays four or more clues during the HGN test, he/she is 77% likely to have a BAC of 0.10% or greater. See also VII-6. "Original research shows that if a suspect exhibits two or more of the clues [during the walk-and-turn California DUI FST], or cannot complete the test, the suspect's BAC is likely to be above 0.10. This criterion has been shown to be accurate 68 percent of the time." See also same. "The original research shows that, when a suspect produces two or more clues [on the one-leg stand California DUI FST] or is unable to complete the test, it is likely that the BAC is above 0.10. This criterion has been shown to be accurate 65 percent of the time."
4 Id., See also Stuster &Burns, Validation of the Standarized Field Sobriety Test Battery at BACs Below .10 percent. U.S. Dept. of Transportation Rep. No. Dot-HS-808-839 (1998), at 33; Burns & Moskowitz, Psychophysical Tests for DWI Arrest, U.S. Dept. of Transportation Rep. No. DOT-HS-802-424 (1977) (recommended the three-test battery of one-leg stand, walk and turn, and HGN to aid officers in discriminating BAC level); Anderson, Schweitz & Snyder, Field Evaluation of Behavioral Test Battery for DWI, U.S. Dept. of Transportation Rep. No. DOT-HS-806-475 (1983) (field evaluation of the field sobriety test battery (HGN, one-leg stand, and walk and turn) conducted by police officers from four jurisdictions indicated that the battery was approximately 80% effective in determining BAC above and below .10 percent).
5NHTSA Student Manual (2006) at VIII/1
7 Id., at VIII / 4
8 Id., at VIII / 4
9 Wilkinson, Kime & Purnell, Alcohol and Human Eye Movement, 97 BRAIN 785 (1974) (oral dose of alcohol impaired eye movement of all subjects); Lehti, The Effect of Blood Alcohol Concentration on the Onset of Nystagmus, 136 BLUTALKOHOL 414 (West Germany 1976) (noted a statistically significant correlation between the BAC and the angle of onset of nystagmus with respect to the midpoint on the field of vision).
10NHTSA Student Manual (2006) at VII/3
11 Id., at VII/4
12 Id., at VII/4
13 Id., at VII/4
14 Id., at VIII/9
15 Id., at VIII/9
16 Id., at VII/5
17 Divided attention tests are especially helpful because suspects who are intoxicated tend to have difficulty with tasks that require their attention to be divided between mental and physical tasks.
18 Id., at VIII/13
19 Id., at VIII/14
20 Id., at VII/6
21 California Highway Patrol (December 2007). Memo Re: HPM 70.4. Driving Under the Influence Enforcement Manual. The hand pat test was among the six optimal DUI field sobriety tests that were examined during the initial 1977 study conducted by SCRI. The hand pat test was also included in a Finnish DUI study conducted in 1974 and was implemented by the LAPD during the formation of their DRE program. The hand pat test is noted for its divided attention qualities and depth perception issues.
22 Although the hand pat test has not been tested under government-approved scientific conditions, experienced California officers have indicated that is it an effective and reliable field sobriety test.
23 Id., The Finger to Nose field sobriety test differs from the other DUI psychophysical tests in that the examiner must continue to give instructions to the subject throughout the test.
25 Id., Experienced California officers have indicated that the Rhomberg balance test is an accurate and effective field sobriety test despite the fact that the Rhomberg balance test has not been tested under national government-approved scientific conditions.
27 Id., Experienced California officers have indicated that the finger count test is an efficient and effective field sobriety test in spite of the fact that the finger count test has not been tested under federal government-approved scientific conditions.
29NHTSA Student Manual (2006) at VIII/10
32 Id., at VII/7
33NHTSA Student Manual (2006) at VIII/14
34 Id., at VIII/13
35 John Murray is a DUI criminal defense attorney qualified by NHTSA to administer field sobriety tests, in connection with DUI roadside investigations. Mr. Murray practices in Ventura and Los Angeles Counties, including Simi Valley, Van Nuys, San Fernando, Lancaster, Glendale and Burbank.
36 Having instructed literally thousands of polices officers and hundreds of attorneys (dui defense lawyers & prosecutors alike) in the proper administration of field sobriety tests, Mr. LaPier is highly qualified in exposing and subsequently teaching the inherent weaknesses of the various DUI field sobriety tests.
37 FSTs are generally difficult to perform correctly, even for a perfectly sober person.