DUI Field Sobriety Tests
DUI field sobriety tests (“FSTs”) are designed to help law enforcement officers identify intoxication due to alcohol and/or drug use. Poor performance on these exercises (as well as difficulty following the officer’s instructions) is thought to be a sign of mental and physical impairment stemming from alcohol or drug consumption.
Officers heavily rely on FST exercises as a part of their DUI investigations. So do district attorneys as part of their prosecutions. But these tests are, in fact, notoriously flawed and unreliable.
Indeed, even the most trustworthy field sobriety tests are only between 65-77% accurate at detecting whether the driver is intoxicated.1 This means that, on average, one out of every three or four people who get arrested for DUI based on failing the FSTs are innocent.
This is just one of the reasons why it is critical to consult with a DUI defense attorney if you have been arrested for driving under the influence after you performed field sobriety tests.
The following is a brief summary about DUI field sobriety testing. Topics that we address include:
The National Highway Traffic Safety Administration’s Role with Respect to DUI Field Sobriety Testing
The NHTSA “Standard” Three
DUI Field Sobriety Tests: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and The One-Leg Stand
Non-standardized DUI Field Sobriety Tests
If, after reading this article, you would like more information, we invite you to contact us at Shouse Law Group.
You may also find helpful information in our related articles 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.
The National Highway Traffic Safety Administration’s Role with Respect to DUI Field Sobriety Testing
The National Highway Traffic Safety Administration (NHTSA) is the federal agency that issues police protocols for DUI field sobriety testing. NHTSA has concluded that there are three FSTs that, when precisely administered, are reliable enough to gauge “accurately” whether an individual is too mentally and/or physically impaired to drive safely. These are referred to as the “standardized” field sobriety tests.2
However, there are several problems with this conclusion, all of which are critical to fighting a DUI charge:
- These tests are rarely, if ever, “precisely” administered. In fact, many officers have never even personally received NHTSA training in how to explain, monitor, or score the standardized field sobriety tests.
- A 65-77% accuracy rate hardly seems accurate according to any type of scientific standard.
- There are a variety of factors, other than alcohol intoxication, that can adversely affect one’s performance on FSTs. Factors such as
- inclement weather,
- poor lighting,
- uneven surface conditions,
- the distraction of traffic, lights, and spectators,
- unstable or unsecure footwear,
- fatigue,
- one’s weight, age, physical condition, and natural coordination,
- nerves,
- intimidation,
- the vagueness of the officer’s instructions,
- sickness, and/or
- injury
can all cause an otherwise sober person to perform poorly on his/her FST exercises.
Nonetheless, the horizontal gaze nystagmus (HGN), walk-and-turn, and one-leg stand field sobriety tests…all of which are described below…are still considered the most reliable of the FSTs.3
Even so, a skilled DUI defense lawyer will still challenge:
- the manner in which the tests were administered,
- the inherent bias of DUI officers (who typically fail to report all of the things which the individual did correctly), and
- the fact that there are a host of innocent explanations (some of them listed above) that can explain a person’s poor performance on the FSTs…factors the officer probably never took the time to consider…and factors that we will surely bring to the jury’s attention.
The NHTSA “Standard” Three DUI Field Sobriety Tests: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and The One-Leg Stand
The horizontal gaze nystagmus (HGN) DUI field sobriety test
The reportedly 77% accurate horizontal gaze nystagmus field sobriety test is an eye exam.4 During this FST, the officer looks to see at what point the suspect’s pupils begin to involuntarily bounce or jerk when they track an object.
Although many people will display jerking at some point close to the outer edges of the eye, a person who is intoxicated will display this jerking before the eye looks to a 45 degree angle.5
The walk-and-turn DUI FST
During the walk-and-turn field sobriety test, the officer observes how well the suspect can balance and follow directions. The individual is directed to
- take nine heel-to-toe steps on a real or imaginary line,
- pivot around, and
- take nine heel-to-toe steps back,
all while keeping his/her arms down and counting the steps aloud. The officer looks for eight clues that indicate impairment. If the person displays two or more of these, NHTSA reports that there is a 68% likelihood that the individual has a BAC of 0.10% or more.6
The one-leg-stand DUI field sobriety test
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.
While the officer observes the individual, he/she watches for five clues that indicate impairment. According to NHTSA, there is a 65% chance that a person who displays two or more clues is DUI.7
Non-standardized DUI Field Sobriety Tests
In addition to the three FSTs explained above, 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 field sobriety tests and DUI impairment. Therefore opinions as to whether…and to what extent…these remaining field sobriety tests properly gauge the intoxication levels of DUI suspects are nothing more than speculation.
These remaining “popular” non-standardized drunk driving FSTs include (but are not limited to):
The hand-pat FST
During the hand-pat field sobriety test, the officer instructs the suspect to extend one hand out in front of him/her, palm side up. The other hand should be placed on top, palm side down. The top hand then “pats” the bottom hand.
The top hand continues “patting” the bottom hand, alternating between palm side up and palm side down while the bottom hand remains still. During this exercise, the suspect counts aloud “one, two, one, two…” in sequence with each “pat”. This FST continues for about 10-15 seconds.
The finger-to-nose DUI field sobriety test
During the finger-to-nose field sobriety test, the officer instructs the suspect to touch the tip of his/her nose with the tip of his/her index finger while keeping the eyes closed and head slightly tilted back.
Throughout this test, officers monitor the suspect’s ability to follow directions and his/her physical coordination. The officer also observes involuntary physical clues, including the suspect’s muscle tone and the presence of eyelid tremors (both of which officers attribute to impairment).
The Rhomberg balance FST
The Rhomberg balance field sobriety test evaluates the DUI suspect’s internal clock. During this DUI FST, the officer instructs the suspect to estimate 30 seconds while keeping his/her eyes closed and standing still with his/her head slightly tilted back.
Some drugs reportedly “speed up” one’s internal clock, while others (including alcohol) reportedly slow it down.
The finger count field sobriety test
During the finger count FST, the officer instructs the DUI suspect to touch his/her thumb to the tip of his/her index finger and say “one”. The suspect repeats this process with each finger tip, counting in succession. Once the suspect reaches his/her little finger, he/she reverses the process, counting back from 4 to 1.
As acclaimed Los Angeles DUI defense lawyer John Murray explains8, “Unlike the “NHTSA 3”, these remaining field sobriety tests have no uniform method of administration, nor any scientific data to support their use. As a result, I always aggressively attack the findings from these and any other non-standardized FST.”
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.
Our California DUI law offices are located in and around Los Angeles, Orange County, Riverside, San Bernardino, Ventura, San Jose, Oakland, the San Francisco Bay area, and several nearby cities.
Our Nevada DUI law offices are located in Las Vegas and Reno.
Online Resource:
National Highway Traffic Safety Administration: Development of a Standardized Field Sobriety Test
Legal References:
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.”
2 See same at VII-2. “Horizontal Gaze Nystagmus is the most reliable field sobriety test.” See same at VII-4. “Two divided attention field sobriety tests that have proven accurate and effective in DWI detection are the walk-and-turn and the one-leg stand.”
3 See same.
4 See endnote 1, above.
5 See same at VII-3. “Onset of nystagmus prior to 45-degrees is another clue of impairment.”
6 See same at VII-5. “Officers observing the walk-and-turn [California DUI field sobriety] test observe the suspect’s performance for eight clues: can’t balance during instructions; starts too soon; stops while walking; doesn’t touch heel-to-toe; steps off line; uses arms to balance; loses balance on turn or turns incorrectly; and takes the wrong number of steps.” See also endnote 1, above.
7 See same at VII-6. “Officers carefully observe the suspect’s performance [during the California one-leg stand DUI FST] and look for four specific clues: sways while balancing; using arms to balance; hops; puts foot down.” See also endnote 1, above.
8 Los Angeles DUI defense lawyer John Murray defends clients accused of DUI in Beverly Hills, Burbank, Glendale, Lancaster, Long Beach, Los Angeles, Pasadena, Pomona, Torrance, Van Nuys, West Covina, and Whittier
