Field sobriety tests are a series of assessments administered by a police officer and performed by an individual suspected of driving while intoxicated. Field sobriety tests can involve a wide variety of physical and mental exercises which must be performed on the spot by the driver.
There are two kinds of field sobriety tests: standard and non-standard. The standard field sobriety tests are three assessments approved by the National Highway Traffic Safety Administration (NHTSA). Non-standard field sobriety tests are any other tests outside of this officially approved set. The official field sobriety test gauntlet consists of the horizontal gaze nystagmus examination, the walk-and-turn, and the one-leg stand.
The horizontal gaze nystagmus examination is performed by an officer who slowly moves a pen or other object to the horizontal extremes of a subject’s field of view and asks for them to focus on it. The officer is looking for any inability to follow the moving object smoothly, any distinct eye jerking when the eye is focusing at the extreme points of vision, and jerking eye movements within 45 degrees of straight forward gaze.
The walk-and-turn is a physical examination in which the subject must take nine steps moving heel-to-toe in a straight line, turn on one foot, and walk back the same way. The theory is that an intoxicated individual does not have the balance or ability to split focus and will either fall down or fail to walk in a straight line.
The one leg stand is another examination designed to take advantage of the theoretical disturbance of balance that an intoxicated person is suspected to have. The subject must stand with one leg six inches off the ground and count to 30 without swaying, using their arms for balance, hopping, or putting the foot down.
While these are the NHTSA’s official standardized tests, they are not scored on any particular rubric and officers do not have to use them. Other, non-standard field sobriety tests could include any number of tests of the driver’s memory, cognition, motor skills, or ability to focus. Some common non-standard field sobriety tests include:
All of these tests are seen as valid by a court of law as long as the officer believes it will help indicate whether an individual is intoxicated.
Field sobriety test results are admissible in court whether the officer in question used the NHTSA standardized test or not. This is because, fundamentally, a field sobriety test is entirely made up.
The court is not auditing a driver’s performance on a field sobriety test. How the individual performed is almost entirely incidental because there is no standard metric by which to measure performance. The officer cannot take a baseline test of how the individual would act when not under police scrutiny, they only have the behavior of an individual that they already pulled over under suspicion of being intoxicated.
An officer of the law has every incentive to find that a driver failed a field sobriety test in order to establish the probable cause necessary to compel a blood alcohol content (BAC) test and initiate an arrest. At trial, the officer can describe any number of subjectively observed details such as smelling booze on the breath of the driver, noting a dazed or confused expression on their face, or vague swaying while the officer was talking to them. The officer will then cite their own expertise in knowing how intoxicated people act and submit their testimony as ironclad proof of intoxication.
Detractors of field sobriety tests argue that they are not objective enough to be accurate and rely on an officer’s interpretation of facts. Notably, the horizontal gaze nystagmus examination has been criticized by optometrists who themselves regularly struggle to accurately diagnose nystagmus even in laboratory settings. Additionally, there is no solid evidence that demonstrates that a sober person would reliably perform better at these tests than an intoxicated person. There are a variety of injuries, medical conditions, or obfuscating factors such as performance anxiety that could cause a driver to “fail” a roadside sobriety test for reasons that are wholly unrelated to the question of intoxication.
While a failed field sobriety test can be damning in a DUI trial, they are not required by law. Because a field sobriety test is voluntary, a driver may politely decline or ask to speak to an attorney rather than submit to one.
Field sobriety tests can appear unassailable when presented by the prosecution. That’s why if you are facing a DUI charge and the prosecution plans on using a field sobriety test, you will need an experienced DUI attorney on your side.
A DUI attorney can challenge the results of a field sobriety test, possibly expelling it from evidence if it was not a standard version, or subpoenaing the dash cam footage of the event to prove whether or not you actually failed the test at all. Even if the field sobriety test was a “failure” an experienced DUI attorney can present expert testimony to demonstrate the flaws with field sobriety tests while cross-examining the arresting officer to find holes and embellishments in their story.