In Pennsylvania, an officer who suspects impaired driving may ask you to perform field sobriety tests during a traffic stop. These roadside tests help the officer decide whether to make a DUI arrest. The most common standardized tests include the horizontal gaze nystagmus, walk-and-turn, and one-leg stand.
Officers use these tests to look for signs of impaired balance, coordination, and divided attention. However, field sobriety tests do not measure blood alcohol content, and many factors unrelated to alcohol can affect performance.
What problems can cause false positive results in field sobriety tests?
Field sobriety tests often take place on the side of the road at night. Conditions rarely resemble a controlled environment. Several external factors can affect how you perform:
- Uneven terrain, such as soft gravel or sloped pavement
- Poor lighting from headlights or flashing patrol lights
- Loud traffic or other distractions
- Weather conditions such as rain or snow
- Anxiety or nervousness
Physical conditions can also interfere with performance. Inner ear problems, back or knee injuries, neurological conditions, and certain medications can affect balance and eye movement. One’s fitness makes tasks like standing on one leg more difficult, even when a driver remains sober.
Human error plays a role as well. An officer may give unclear instructions, demonstrate the test incorrectly or score the results improperly. The National Highway Traffic Safety Administration sets guidelines for standardized testing, but officers must follow those procedures closely for the results to carry weight in court.
How to protect your rights if you receive a false positive result
If an officer arrests you after roadside testing, stay calm and polite. In Pennsylvania, the implied consent law under Pennsylvania Consolidated Statutes Title 75 Section 1547 requires drivers to submit to a chemical test after a lawful DUI arrest. Refusal can trigger a license suspension and other penalties.
Field sobriety tests remain voluntary in Pennsylvania. Officers often use them to build probable cause, but prosecutors must still prove impairment beyond a reasonable doubt.
Challenging a DUI charge after receiving a false positive result
To challenge a DUI based on questionable roadside testing, document the conditions as soon as possible. Note the road surface, weather, lighting, and any medical issues that affected your balance or coordination. Medical records and expert testimony can help explain performance issues unrelated to alcohol.
Field sobriety tests can support an arrest, but they do not guarantee guilt. Careful review of the stop, the testing conditions and the officer’s procedures can form a strong defense.
