Many drivers assume that failing a field sobriety test means a DUI arrest is inevitable. In reality, these roadside tests are far from foolproof. While officers often rely on them during traffic stops, field sobriety tests are not precise scientific measurements. They are observational tools that can be influenced by many factors unrelated to alcohol or drugs.
Understanding how these tests work is the first step toward understanding why they are often challenged in court.
What Are Field Sobriety Tests?
Field sobriety tests (FSTs) are roadside exercises used by police officers to assess whether a driver may be impaired. Officers usually request them after observing driving behavior or physical signs that raise suspicion of intoxication.
Unlike breathalyzers, which measure alcohol concentration, field sobriety tests evaluate coordination, balance, and the ability to follow instructions. Officers look for signs such as swaying, missed steps, or difficulty completing the assigned tasks.
Because the results depend on officer observation rather than a measurable reading, the evaluation is inherently subjective.
The Three Standardized Field Sobriety Tests
The most widely used tests are based on guidelines developed by the National Highway Traffic Safety Administration (NHTSA). Officers are trained to administer three standardized tests designed to reveal potential signs of impairment.
1. Horizontal Gaze Nystagmus (HGN)
The Horizontal Gaze Nystagmus test examines involuntary eye movement. During the test, an officer asks the driver to follow a small object, such as a pen or flashlight, with their eyes while keeping their head still.
The officer watches for jerking movements in the eyes known as nystagmus. Alcohol can exaggerate this movement, which officers may interpret as a sign of impairment.
2. Walk-and-Turn
The Walk-and-Turn test evaluates coordination and the ability to follow instructions. The driver is asked to take several heel-to-toe steps along a straight line, turn in a specific way, and repeat the process.
Officers typically look for indicators such as:
- Losing balance while listening to instructions
- Starting the test too soon
- Missing heel-to-toe contact
- Stepping off the line
- Using arms for balance
These observations may be recorded as clues of possible impairment.
3. One-Leg Stand
In the One-Leg Stand test, the driver must raise one foot several inches off the ground and hold the position while counting out loud for a set period of time.
Officers look for behaviors that may suggest difficulty maintaining balance, including:
- Swaying
- Using arms for stability
- Hopping
- Putting the foot down early
Like the other tests, the evaluation is based entirely on what the officer observes.
Are Field Sobriety Tests Required in Maryland?
Field sobriety tests are voluntary in Maryland. Drivers are not legally required to perform them during a traffic stop.
Many drivers assume they must comply with every request made by an officer, but roadside coordination tests are generally optional. Declining them does not trigger the automatic administrative penalties that apply to certain chemical tests.
However, refusing a field sobriety test does not end the investigation. Officers may still note the refusal in their report and rely on other observations to decide whether to make a DUI arrest.
It is also important to distinguish field sobriety tests from chemical testing. Maryland’s implied consent law applies to breath or blood tests after a lawful DUI arrest, not to roadside coordination exercises.
Why Field Sobriety Tests Are Frequently Challenged in Court
Field sobriety tests are often challenged in DUI cases because several factors can affect how a person performs them.
Subjective Interpretation
Field sobriety tests do not produce objective data. Officers decide whether a driver showed “clues” of impairment based on their own observations. Because these judgments can vary from officer to officer, the interpretation may be questioned in court.
Medical or Physical Conditions
Many medical conditions can affect balance or coordination. These may include:
- Inner ear disorders
- Knee or back injuries
- Neurological conditions
- Age-related mobility limitations
Even stress or nervousness during a traffic stop can make the tests harder to perform.
Environmental Conditions
Roadside tests rarely occur under ideal conditions. Drivers may be asked to perform them on uneven pavement, gravel shoulders, or poorly lit roadsides.
Weather, passing traffic, flashing patrol lights, and other distractions can also make the tests more difficult.
Improper Test Administration
Officers are expected to follow specific procedures when administering standardized field sobriety tests. If instructions are incomplete or the test is conducted incorrectly, the reliability of the results may be questioned.
Video footage from dashcams or body cameras is often used to review how the tests were administered.
Officer Training
The officer’s training may also become an issue in court. Prosecutors may need to show that the officer was properly trained to administer and interpret the standardized tests.
If training records are incomplete or the procedures were not followed correctly, the credibility of the test results may be reduced.
What Happens If You “Fail” a Field Sobriety Test in Maryland?
Failing a field sobriety test does not guarantee a DUI conviction. In most cases, these tests are only one piece of evidence among many.
Defense attorneys may challenge the administration of the tests and whether external factors affected the driver’s performance. Video footage, witness testimony, and other evidence can sometimes contradict an officer’s observations.
The state must still prove impairment beyond a reasonable doubt. Because of that high standard, DUI cases often involve careful review of what happened during the roadside investigation. An experienced Annapolis DUI lawyer may examine each step of the stop to determine whether the evidence supports the charge.
What to Do If Asked to Perform a Field Sobriety Test
Being stopped on suspicion of DUI can be stressful. Knowing your options in advance can help you remain composed.
If an officer asks you to perform field sobriety tests:
- Remember that the tests are voluntary in Maryland
- Remain polite and calm during the interaction
- Avoid trying to prove sobriety through tests performed under roadside conditions
- Contact a DUI defense attorney as soon as possible after an arrest
Field sobriety tests may play a role in DUI investigations, but they are not definitive proof of impairment. Understanding their limitations helps explain why these tests are frequently challenged in court.
