You may have heard of field sobriety tests but have questions like: What are they? Do I have to take them? And most importantly, are they accurate?

Knowing the answers to these questions could be pivotal in your criminal case. The criminal defense attorneys at Crawford and Boyle, LLC have over 50 years of combined experience, so we know the ins and outs of these tests and other legal issues that could affect your case. Contact us today for a free consultation.

What Are Field Sobriety Tests?

Field sobriety tests are tests that law enforcement officers use to assess someone’s mental or physical impairment. They are most often used in cases involving suspected drunk driving or drugged driving.

Some of these tests are considered divided attention tests. Such tests require the test subject to divide their ability between following simple instructions and performing those instructions. A person has to perform two tasks at the same time. The justification for these tests is that impaired individuals sometimes have difficulty dividing their attention.

Why Do Law Enforcement Officers Use Field Sobriety Tests?

Anyone asked to perform a field sobriety test should understand that the purpose of these tests is to find someone impaired, not to prove that they are not. When law enforcement officers administer these tests, they are critically looking for clues of impairment. This is because they must have probable cause to justify an arrest, and a failed test result can help provide this necessary probable cause.

The Three Standardized Tests

While field sobriety tests can take many different forms, the National Highway Traffic Safety Administration (NHTSA) only recognizes three.

Walk and Turn

In the walk and turn test, the person pulled over is asked to take nine steps, heel to toe, along a straight line, turn, and return. While the subject performs this test, the police officer is monitoring for the following possible signs of impairment:

  • Loss of balance during instruction
  • Starting the test too soon
  • Stopping while walking
  • Missing a heel-to-toe step by more than ½ inch while walking
  • Stepping off the line
  • Using arms to balance at six inches or more
  • Turning improperly
  • Taking the wrong number of steps

If the test subject shows two or more of these clues, the implication is that they are impaired. Law enforcement officers are instructed to list only the clues that they see, as well as other observations that indicate impairment.

One-Leg Stand

In the one-leg stand test, the subject is instructed to stand on one foot for 30 seconds while counting. The clues of impairment law enforcement officers are looking for in this test are:

  • Swaying: Movements such as swaying or wobbling that indicate that the subject is having difficulty maintaining their balance
  • Using arms to balance: Raising or using arms more than six inches to balance
  • Hopping: The subject hops to prevent themselves from falling
  • Putting the foot down: The foot is put down on the ground before the subject finishes counting to 30

If the subject exhibits at least two out of these clues, the inference is that they are impaired. Police officers also note other observations that indicate impairment, such as miscounting or not holding the foot parallel to the ground.

Horizontal Gaze Nystagmus

The Horizontal Gaze Nystagmus (HGN) test tracks involuntary jerking of the eyes as they follow an object. Law enforcement officers look for the following clues in each eye for a total of six possible clues:

  • Lack of smooth pursuit
  • Distinct and sustained nystagmus (involuntary, rapid, and repetitive eye movements) at maximum deviation
  • Onset of nystagmus before 45 degrees

The inference is that the subject is impaired if they exhibit four or more clues.

Do I Have to Take Field Sobriety Tests?

No. Many people are confused about their legal rights and obligations when stopped for suspected DUI. For example, they may believe that the implied consent law requires them to take these tests, but that’s not true.

The implied consent law conditions a person’s right to drive in the state by their agreement that they will be subject to blood or breath tests if they are suspected of driving under the influence of drugs or alcohol. If they refuse, they can lose their driving privileges. However, the law does not apply to field sobriety tests. It also does not apply in Georgia until after an arrest.

Therefore, no, you are not legally required to take field sobriety tests.

Accuracy of Field Sobriety Tests

Field sobriety tests are not 100% accurate. In fact, their accuracy is largely disputed by their proponents and opponents.

What the NHTSA and Law Enforcement Say

The NHTSA hired the Southern California Research Institute (SCRI) to conduct foundational research for it to develop and validate the standardized field sobriety tests. The NHTSA analyzed this research and found the following levels of accuracy:

  • HGN: 77% accurate on its own
  • Walk-and-turn test: 68% accurate on its own
  • One-leg stand: 65% accurate on its own

However, the NHTSA has continued to research this issue and now cites the following levels of accuracy:

  • HGN: 88% accurate on its own
  • Walk-and-turn test: 79% accurate on its own
  • One-leg stand: 83% accurate on its own

The NHTSA also claims that the accuracy increases when the test results are used together, with an overall accuracy rate for the combined battery of standardized field sobriety tests at 81% to 91%. The NHTSA also cites a Colorado Field Validation Study of the SFSTs, claiming a 86% correct arrest and release decision based on the three-test battery and that 93% of those arrested had a BAC of 0.05 or higher. It also cites a Florida Field Validation Study of the tests, which found a 95% correct arrest decision based on the three tests.

What Other Researchers Say

Despite the statistics above, many people criticize the SFSTs and their estimated accuracy. Some of the most common arguments against them include the following:

Strict Requirements

Police officers conducting these types of tests must follow strict guidelines. The NHTSA warns that the tests must be administered in the prescribed, standardized manner and that if any one of the standardized field sobriety test elements is changed, the validity of the test result is compromised.

Scientific Foundation of the Tests

An expert told news reporters that the original research conducted to adopt the standardized tests did not meet the requirements for peer-reviewed scientific publication. They report that the research never went through the standard academic peer review process for publication in a peer review journal.

Additionally, problems in the research methodology further raise questions regarding the tests’ accuracy. There was not a randomization of test subjects. For example, most of the subjects were younger males, with fewer women, people of color, and older populations underrepresented. Additionally, the expert argues that there had to be suitable controls in place, including people who had not been drinking, when conducting the research.

The expert also said that the research failed to account for age, medical conditions, medications, physical characteristics, and other factors that can affect how someone performs on the tests.

Qualifications of Test Administrators

The expert also argued that law enforcement officers are not usually qualified to perform these tests because they are neurological examinations that should be performed by someone with medical training. The people primarily responsible for developing the SFSTs also do not have this training.

In particular, the horizontal gaze nystagmus test can result in inaccurate test results when the person administering the test does not understand abnormal eye movements, diseases or medications that can affect eye movement, or other core medical concepts. Another expert who also spoke to reporters said that trained doctors use the horizontal gaze nystagmus test to detect neurological disorders in patients and that using it from untrained police officers in the field had exploited the test for improper purposes. 

Test Limitations

The experts also believe that the NHTSA and law enforcement have not been transparent about the tests’ limitations. They argue that they are not accurate enough to be used as evidence in court and may be responsible for the arrests of innocent, sober people.

One of the creators of the tests in sworn testimony said that the tests were designed to help officers make quick roadside decisions. This leads researchers to criticize the tests because they don’t accurately eliminate drivers who are not impaired. Sober people have been known to fail these tests.

For example, the walk-and-turn test and one-leg stand require movements the human body is not naturally designed to perform, so many people fail these tests, regardless of sobriety. A former law enforcement trainer told reporters that sober people routinely struggle with these tests, citing a research study in the Journal of Forensic Toxicology and Pharmacology that found a 26% false positive rate for sober test subjects.

Road Conditions

Road conditions can also impact the reliability of these tests. If the pavement is not perfectly level, this can affect balance and the ability to perform the tests well. If it had recently rained or snowed, the pavement could also be wet and slick, causing additional issues that can lead to inaccurate results.

Confirmation Bias

When law enforcement officers conduct these tests, they are doing so to confirm their suspicions that the driver was impaired. They are looking for clues that support their hunch. Because officers score the tests based on these clues, the scoring is more subjective, further underscoring its potential for a lack of accuracy.

Medical and Physical Conditions

Various medical issues, physical factors, and medications can affect a subject’s performance on these tests, such as:

  • Being aged 65 or older
  • Being overweight
  • Vertigo, inner-ear issues, or other medical issues that cause balance issues
  • Injuries or medical issues affecting the back or leg
  • Anxiety or nervousness
  • Dehydration
  • Fatigue
  • Comprehension issues
  • Difficulty following multiple tasks at a time
  • Prescription and over-the-counter medications

How an Experienced DUI Lawyer Can Help

An experienced DUI defense attorney understands the limitations of these tests and can use their investigative skills to question their validity. Some tactics may be to:

  • File a motion to suppress evidence if the stop was not valid or the police officer had insufficient probable cause for an arrest
  • Review police reports and test records
  • Challenge an illegal stop or arrest
  • Challenge the reliability of the evidence, based on some of the issues with the original research
  • Gather evidence of a medical condition that could have caused the poor test results
  • Use unreliable test results as leverage for a favorable plea bargain
  • Cross-examine the police officer on the test administration and their experience performing these tests
  • Show video evidence of the tests that contradicts the law enforcement officer’s sworn testimony
  • Push for a dismissal or reduction of a charge

At Crawford and Boyle, LLC, we have over 50 years of combined legal experience. Contact us today to learn about the effective defense strategies that we can put in place to aggressively defend your rights.

Call Today to Schedule a Free Consultation

Crawford and Boyle, LLC offers free consultations to people who were arrested for a crime. We know how confusing and intimidating the legal process is, so we try to help you feel more comfortable by offering a free case evaluation where we can explain the nature of the charges against you and answer any questions that you have, all at no cost or obligation to you. Contact us today to get started with yours.