The Only 3 Effective DUI Field Tests
Police officers use field sobriety tests (“FSTs”) when they stop a driver suspected of being under the influence of drugs and/or alcohol. The three standardized field sobriety tests (“SFSTs”) are considered the most reliable FSTs and the tests recommended by the National Highway Traffic Safety Administration for use by law enforcement agencies. However, police officers also use non-standardized field sobriety tests. Unfortunately, all tests have potential issues that can make the results unreliable.
The Purpose and Types of DUI Field Sobriety Tests
How do police officers use field sobriety tests during DUI investigations in California?
California uses the three standardized field sobriety tests to conduct DUI investigations during traffic stops. The purpose of conducting the tests is to determine whether a driver is impaired. The tests also serve to provide probable cause for a DUI arrest. A police officer must have probable cause to believe the person is intoxicated before making a lawful DUI arrest.
Three tests were chosen as standardized field sobriety tests. Each test has specific instructions and procedures for giving the test to a driver. Any deviation from the procedures could make the test results inaccurate and unreliable. Those three tests are: (1) Horizontal Gaze Nystagmus Test (“HGN”); (2) Walk and Turn Test (“WAT”); and (3) One-Leg Stand Test (“OLS”).
Horizontal Gaze Nystagmus Test (“HGN”)
The Horizontal Gaze Nystagmus Test checks for involuntary “eye jerking” or nystagmus, which occurs when a person looks to the side without turning their head. The severity of the “jerking” increases when a person is intoxicated. An HGN test can also detect when a person has consumed certain prescription medications and illegal drugs.
The police officer performs the test by instructing the person to focus on a stimulus, which is usually a small object, finger, or pen. The officer moves the stimulus horizontally across the person’s line of sight about a foot to 15 inches away. As the driver’s eye follows the object, the police officer watches for signs of increased nystagmus including:
- Inability to follow the object smoothly;
- Distinct jerking at maximum deviation; and
- Substantial eye jerking within a minimum of 45 degrees from the center.
The officer looks for the signs in each eye, checking for six total signs of increased nystagmus.
Walk and Turn Test (“WAT”)
The Walk and Turn Test is the test most people are familiar with due to its depiction in movies and television. During the WAT, a police officer instructs the driver to take nine steps along a straight line, turn around, and then take nine steps back to the starting point. The steps must be heel-to-toe steps. The officer instructs the driver to count the steps out loud as they take each step. The officer watches for eight indications that the person might be impaired:
- Inability to balance while listening to instructions;
- Making an improper turn;
- Beginning to walk before the officer instructs the person to begin the test;
- Taking the wrong number of steps;
- Stopping to regain balance while walking;
- Stepping out of line;
- Failing to touch the heels to the toes; and
- Using the arms for balancing.
The standardized instructions state that if the person displays at least two of the eight indicators, they fail the walk-and-turn test.
One-Leg Stand Test (“OLS”)
The police officer instructs the person to stand still and lift one foot off the ground about six inches. The officer instructs the person to count by one until the officer tells them to stop while holding their foot off the ground. The standardized instructions state the officer should time the suspect and stop them in 30 seconds. The officer looks for four indicators of impairment:
- Hopping during the test;
- Repeatedly swaying during the test;
- Putting their foot down one or more times; and
- Using the arms to maintain balance.
The standardized instructions state that committing two or more of the four indicators means the person failed the one-leg stand test.
Field Sobriety Tests: Potential Problems and Challenges
Even though the above tests are widely considered reliable indicators of driving under the influence, there are many problems with the tests. Critics cite issues with the accuracy and reliability of test results. They also question environmental factors and the actions of police officers that could result in flawed test results.
What Do the Tests Mean if You Fail?
The police officer should refer to their FSTs training to determine if the person “failed” a field sobriety test. As indicated above, specific instructions in the training materials indicate when a person has “failed” the test.
If the officer decides that you failed one or more of the FSTs, the officer will likely state they have probable cause for a DUI arrest. The officer may then ask the driver to take a preliminary alcohol screening (“PAS”) test, which is generally a field breathalyzer machine. A BAC (“blood alcohol content”) level on the breathalyzer gives the officer additional probable cause to make an arrest for DUI.
After a lawful DUI arrest, California’s implied consent laws require individuals to take a chemical test. The police officer should ask the person whether they want to provide a sample for a breath test or a blood test for chemical testing. Urine tests are only used when blood and breath tests are unavailable.
Field Sobriety Tests: Accuracy, Limitations, and Criticism
There are limits to using field sobriety tests during a DUI stop. There are also questions regarding the accuracy of field sobriety tests. Some of the issues that DUI defense attorneys raise regarding the use of FSTs in DUI cases include:
- The accuracy of field sobriety tests;
- Failing to provide clear and correct instructions;
- Environmental factors;
- Medical conditions;
- Being nervous &/or scared; and
- The subjectivity of SFSTs.
The Accuracy of Field Sobriety Tests
Several studies have been conducted on the accuracy of FSTs in determining whether a driver is impaired by alcohol and/or drugs. The NHTSA Instructor Guide for the tests explains that three studies were conducted between 1995 and 1998. The studies were conducted in San Diego, Florida, and Colorado. Each study resulted in different conclusions regarding the accuracy of FSTs.
The Instructor Manual states that officers should use the San Diego Field Validation Study when testifying in court. That study indicated the following accuracy rates:
- HGN tests were 88% accurate;
- OLS tests were 83% accurate; and
- WAT tests were 79% accurate.
Even though the NHTSA claims that the study results provide clear evidence of the validity of standardized field sobriety tests, California DUI defense lawyers disagree. First, these tests are not 100% accurate. Moreover, other scientific tests have shown that the accuracy of these tests is questionable.
One study used sober individuals to perform standardized FSTs. After watching videos of people taking the tests, police officers believed that a significantly larger number of the people were impaired. Another study concluded that the HGN test has a high baseline error and varied greatly depending on whether the person’s BAC level was rising or falling. In 52 videos of DUI arrests, the study authors concluded the HGN test was incorrectly administered 51 times.
Additionally, other factors make the accuracy and validity of the tests questionable.
Failing to Provide Clear and Correct Instructions
The police officer administering the SFSTs must follow the exact procedures for giving the test to a driver. Deviation from the procedures could result in inaccurate results. However, suppose there is no body camera footage, other video footage, or audio evidence that the officer gave the person clear and correct instructions. In that case, there is no way to know if the officer purposefully or unintentionally caused the person to “fail” the field sobriety test.
Numerous environmental factors could invalidate the results of standardized field sobriety tests. For example, the officer should conduct the tests on a level, paved surface. Otherwise, the person may stumble or lose their balance because of the ground, but not because they are impaired by alcohol. Another example is conducting the HGN test with bright lights shining in the person’s eyes from the sun or oncoming traffic. The lights could cause unreliable results.
Another problem to consider is the person’s health condition. A person may have a medical condition that prevents them from passing the test even though they are sober. In addition, a person’s age could cause them to perform poorly on a test even though they are perfectly capable of operating the motor vehicle safely. Physical limitations may prevent someone from “passing” the one-leg stand test or the walk-and-turn test.
Some medications could cause a person to exhibit signs of intoxication even though they are sober and not impaired. For example, some medications for seizures can cause increased nystagmus even though the person is sober. In addition, there are dozens of other possible causes of nystagmus, including hypertension, eye strain, glaucoma, and consuming excessive amounts of caffeine.
Being Nervous and Scared
Merely being nervous about being pulled over and scared of being arrested could cause someone to perform poorly on SFSTs.
SFSTs are Subjective
Whether you fail or pass a sobriety test depends upon the officer’s interpretation of your performance during the tests. In other words, one officer might conclude you were intoxicated and arrest you for drunk driving. Another police officer might conclude that you are not impaired and release you without an arrest. A study conducted using police officers, bartenders, and university community members found that the group had less than a 25% accuracy rate when correctly determining how drunk a person was after observing the targets for several minutes. Furthermore, the accuracy of the ratings worsened as the targets’ level of intoxication increased.
If a police officer has some bias against the person, the officer might unethically or unconsciously interpret the results in favor of probable cause and an arrest. For example, a driver was rude and obnoxious when the officer made the initial traffic stop. The person was critical and uncooperative. In that case, the officer might decide that the person is drunk and make the arrest, even though the results of the SFSTs were borderline.
Non-Standard Field Sobriety Tests
Some jurisdictions also use non-standardized field sobriety tests to determine impairment to support probable cause for a DUI arrest. Police officers claim the non-standard FSTs are reliable because they require the person to utilize split focus and dexterity, which is difficult to do if the person is drunk or drugged. However, these non-standardized tests are unreliable and highly subjective. Some non-standard field sobriety tests used by police officers include:
- Romberg Balance Test – Closing the eyes and tipping the head backward while standing with the feet together, estimating when 30 seconds have passed, and then saying “stop” to the officer.
- Finger-to-Nose Test – Closing the eyes and touching a finger to the tip of the nose.
- ABC Test – Reciting the alphabet forwards or backward.
- Finger-Tap Test – Tap a finger to your thumb as fast as possible with an opening between taps as wide as possible.
- Numbers Backward Test – Counting backward.
- Stand and Gaze Test – Standing and leaning so that the person gazes at the sky while holding their arms to their sides.
- Hand Pat Test – Extend an arm out with the palm facing up and out. Place the other hand on top of the raised palm facing down. Rotate the hands 180 degrees to pat the bottom hand with the back of the other hand before rotating and doing it again while counting “one” and “two” each time.
The NHTSA does not recognize these tests as reliable indicators of whether a person is impaired by alcohol and/or drugs. A skilled California DUI defense attorney will challenge these test results in court. Challenging non-standard field sobriety tests is easier because they are not widely accepted as accurate indicators of intoxication or impairment.
Field Sobriety Test Refusals – Drivers Aren’t Required to Participate in Field Sobriety Tests
No California law punishes a person for refusing to take a field sobriety test. However, a police officer will not tell you this detail. Instead, the officer will only ask you to perform the tests without indicating that you may refuse the test without punishment. Understanding your right to refuse to take a field sobriety test is essential because sober people can fail the tests.
However, there is a difference between field sobriety tests and chemical tests for BAC levels. California’s implied consent laws require drivers to submit to a chemical test of their blood or breath after a lawful DUI arrest. Refusing a chemical test after a DUI arrest results in an administrative driver’s license suspension by the California Department of Motor Vehicles (“DMV”). Your driving privileges are suspended for one year for a first-time refusal of a chemical test. A second refusal within ten years results in a two-year revocation of your driver’s license.
However, if you are under 21 years old or on probation, refusing a chemical test after a DUI arrest of a preliminary alcohol screening (“PAS”) test after being detained results in a one-year driver’s license suspension for the first refusal and two-year revocation for a second refusal within ten years.
California Vehicle Code §23612 states that an officer must advise you that refusing the chemical test could result in a suspension of your driving privileges. Your California DUI attorney might be able to successfully argue against the DMV administrative license suspension if the officer failed to provide the required advisements.
How Field Sobriety Test Results Are Used in Court & Challenging FSTs Results in California
The prosecution uses the results from field sobriety tests in court in several ways. First, the prosecutor may use the FSTs to support the finding that the police officer had probable cause to arrest you for driving under the influence.
If you are charged with driving under the influence, the prosecutor uses field sobriety tests to support the allegation that you were too impaired to drive. This situation often occurs when the driver refuses to take a chemical test. The state does not have evidence of the BAC level at the time of the arrest. Therefore, it must prove that your ability to operate the vehicle was impaired.
When you are charged with DUI per se, the state has BAC test results showing that you were driving with a BAC over the legal limit. Generally, the BAC test results are sufficient to prove the state’s case if there is no valid DUI defense to convince the jury you were not drunk or under the influence of drugs. However, a prosecutor might use the FSTs results as additional evidence you were drinking and driving.
A skilled California DUI lawyer challenges the results of standardized FSTs in court. The attorney might challenge the results in one of several ways including:
- Challenging the reliability of the tests based on data showing a considerable margin for error. The attorney might hire an expert witness to provide testimony regarding the accuracy of the test.
- Providing evidence that the law enforcement officer failed to administer the standard FSTs according to the procedures in the NHTSA manual.
- Offering evidence proving that the test results were negatively impacted by a medical condition, legal prescription medications, or environmental factors.
- Your clothing, lack of sleep, muscle fatigue, advanced age, injuries, weight, or other extraneous conditions caused poor performance on the FSTs.
- The officer administered non-standardized field sobriety tests.
There could be other challenges and DUI defenses in your case. Schedule a free consultation to talk with a DUI lawyer about potential defenses to drunk driving charges.
Talk to a California DUI Defense Attorney
Fighting DUI charges begins with hiring an experienced DUI defense attorney. Contact a criminal defense lawyer for a free consultation to discuss your case. Most attorneys offer a free consultation so that you can get answers to your questions about DUI defense and your legal rights to make an informed decision about how you want to proceed with your DUI case.
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