Law enforcement officers rely heavily on field sobriety tests (FSTs) in California to determine if a driver is impaired by alcohol or drugs during a traffic stop. The FSTs may be the only “evidence” an officer collects during a DUI investigation to justify an arrest for driving under the influence. The theory is that poor performance on field sobriety tests indicates alcohol or drug impairment.
However, these “standardized” field sobriety tests are not perfect. Even if the conditions are ideal and the police officer administers the FSTs precisely as directed by the NHTSA guidelines, the results of field sobriety tests can be inaccurate. According to the Instructor Guide provided by the National Highway Traffic Safety Administration, the accuracy levels for the FSTs are:
- Walk and Turn Test – 79% accurate
- One Leg Stand Test – 83% accurate
- Horizontal Gaze Nystagmus Test – 88% accurate
California drivers need to understand their rights regarding field sobriety tests. For example, a California driver does not have to take the field sobriety tests when stopped for suspicion of drunk driving.
California Drivers Can Refuse to Take Field Sobriety Tests
If you are pulled over for drunk driving, the police officer will ask you to take the field sobriety tests. He is looking for signs of impairment based on your performance on the FSTs. California does not impose any penalty for refusing to take field sobriety tests during a traffic stop.
As experienced DUI defense lawyers, we generally recommend that California drivers respectfully decline to take field sobriety tests for several reasons. Primarily, a sober person can fail a field sobriety test for reasons that have nothing to do with alcohol or drugs in their system.
Unlike chemical tests (i.e., urine, blood, or breath test) that determine your blood alcohol content (BAC), the field sobriety test the officer gives you is a subjective review of “signs” that could indicate you are a drunk driver. The officer may have already made up his mind about arresting you for drunk driving. Taking the FSTs gives the police officer additional “evidence” to present to the court that justifies the DUI charges.
Failing field sobriety tests could result in one or more charges under the California Vehicle Code, including driving under the influence and DUID (driving under the influence of drugs).
To help you understand how California field sobriety tests work and how the results can be incorrect, we discuss the standardized FSTs and some non-standard field sobriety tests used by California police officers during a DUI stop.
DUI Field Sobriety Tests Used in California
As discussed above, the NHTSA has approved three field sobriety tests to be used by police officers during a roadside DUI investigation. The NHTSA considers these tests to be good indicators of a person’s impairment.
The NHTSA bases its “validation” of these tests in part on a study by the Sand Diego Police Department. The study reported a strong connection between poor performance on these tests and alcohol or drug impairment. The tests are collectively referred to as the “standardized FSTs.”
The Walk and Turn Test (WAT Test)
This divided attention test requires a person to simultaneously concentrate on a physical and mental task. For the test to be accurate, the police officer must give the person exact instructions for completing the test. The person must remember the instructions and complete them in order correctly.
Generally, the police officer tells the person to take nine heel-to-toe steps in a straight line (either a line on the road or an imaginary line). After completing nine heel-to-toe steps, turn around and take nine heel-to-toe steps back to the beginning point.
There are eight signs that the police officer may notate that could indicate the person is intoxicated or under the influence of drugs:
- Starts walking too soon
- Cannot maintain balance during the instructions
- Fails to walk in a heel to toe fashion
- Uses the arms to balance
- Takes the wrong number of steps
- Stops while walking
- Steps off the line
- Fails to make the turn correctly
This FST has a 79% accuracy rating for indicating a BAC of .08 or greater because of poor performance. There could be many reasons why a person is unable to maintain balance while walking heel to toe.
The Horizontal Gaze Nystagmus Test (HGN Test)
Nystagmus is the involuntary movement or “jerking” of the eyes from side to side, up and down, or in a circle. Horizontal nystagmus describes the uncontrollable and rapid movement of the eyes from side to side.
The HGN test given during a roadside field sobriety test involves the police officer noting the angel of the eye when it begins to “jerk” (exhibit nystagmus) as it moves side to side. The officer performs the test by moving a stimulus, such as a pen, from left to right and instructing the person to follow the object with their eyes.
Nystagmus at or before the 45-degree angle of the eye movement is associated with a high level of alcohol in the person’s system. However, the accuracy level of the HGN test is roughly 88%, according to the NHTSA. Therefore, the results of this field sobriety tests could be incorrect in at least 12% of the cases.
The One Leg Stand Test (OST Test)
This field sobriety test is another divided attention test used during a DUI traffic stop. While this test has a better accuracy rating according to the NHTSA, it still leaves a lot of room for errors.
During the OLT test, the police officer instructs the person to lift their foot about six inches off the ground. While holding that position, count from 1001 to 1030 and then look down at their foot.
Signs of impairment that the officer looks for during the test include swaying, hopping, using the arms to balance, and putting the foot down before completing the test.
Non-Standard DUI Field Sobriety Tests Used by Police Offices
In addition to the “standardized” field sobriety tests, police officers use various non-standard field sobriety tests during a DUI stop. The NHTSA has not approved or validated these tests because there is little to no evidence that poor performance on these tests indicates DUI impairment. Furthermore, the way the tests are administered can vary significantly from one law enforcement officer to another, increasing the chance that the test results are inaccurate.
Several “signs” the officer looks for when performing these non-standard FSTs include:
- Ability to follow instructions, including counting correctly, starting and stopping correctly, and remembering instructions
- Ability to balance and stand still
- Muscle tone and body/eye tremors
- Depth perception
- Uttering unusual phrases or sounds
- Lack of muscle control
- Ability to perform mental and physical tasks simultaneously
Some of the non-standard field sobriety tests used by California police officers include:
Finger Count Test
The police officer instructs the person to extend their hand with the palm facing upward in front of their body. Then, touch the top of the thumb to each finger, beginning with the index finger and working their way over to the little finger. While touching each finger, the person should count from one to four aloud. Then, the process is reversed for a total of three sets.
Finger to Nose Test
This non-standard FST is one of the most common field sobriety tests officers perform. First, a police officer instructs the person to stand with their feet together and their arms at their sides. Then, after making a fist with each hand and keeping the index finger extended, the person must tilt their head back and close their eyes.
The officer then instructs the person to extend either the left or right arm in front of their body and use their index finger to touch their nose. If the person cannot perform the test correctly, it is thought to be a sign of intoxication because the person lacks muscle control and coordination.
Romberg Balance Test
A police officer instructs the person to stand with their feet together, and their head tilted slightly backward. Then, with their eyes closed, the person must estimate when 30 seconds have passed. Finally, when they believe 30 seconds have passed, they will tilt their head forward, open their eyes, and say stop.
Hand Pat Test
The officer instructs the person to extend either the left or right hand in front of their body with the palm facing upward. Then, place their other hand on the top of that hand with the palm facing down.
Keeping the bottom hand in the same location, the person must use the top hand to “pat” the bottom hand while counting “one, two, one, two, etc.” In addition, the person must rotate their top hand on each of the counts so that they pat their bottom hand palm down on the “one” counts and palm up on the “two” counts.
What Can Affect the Accuracy of a DUI Field Sobriety Test?
Many things can affect the accuracy of DUI field sobriety tests. For example, there are several medical reasons why a person would exhibit signs of nystagmus, including multiple sclerosis, head injuries, certain medications, and cataracts.
Numerous physical and mental conditions may affect the accuracy of a test. Age, weight, inner ear problems, mental disabilities, anxiety, physical pain, and illness are just a few examples of why a person could “fail” a field sobriety test when they are not impaired by alcohol or drugs. In addition, being tired, having muscle fatigue from work or exercise, and stress can negatively impact a person’s ability to perform field sobriety tests correctly.
Weather and field conditions can have a significant impact on FST results. For example, if the test is given on an uneven surface, it increases the chance the person will lose their balance. In addition, bright lights from oncoming traffic and noise can affect test results.
The police officer’s conduct can result in inaccurate test results. For example, if the police officer does not provide clear instructions, the person may “fail” the test. Likewise, if the officer moves around, it can distract the person and result in inaccurate test results.
Even something as simple as wearing high heels, tight clothing, or baggy pants could adversely affect a person’s performance on field sobriety tests.
Fighting the Results of DUI Field Sobriety Tests in California
If you are arrested for DUI in California, you should discuss your legal options with a DUI defense attorney before pleading guilty to driving under the influence. There may be one or more grounds for challenging field sobriety tests.
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