During a drunk driving traffic stop, police officers document the situation to build a criminal case. They may follow a driver who seems intoxicated for several blocks recording their performance at the wheel. They may ask drivers questions that could implicate them.
When they have strong suspicions of intoxication, they may ask a motorist to step out of their vehicle and perform field sobriety tests. Field sobriety tests can provide the basis for criminal charges. A driver’s performance on these tests could give the state evidence to use against them during a criminal trial.
To ensure that the evidence gathered through field sobriety testing is reliable and useful in criminal court, police officers must adhere to best practices. Typically, they can only administer the three standardized field sobriety tests. What tests can officers have drivers perform?
1. The walk-and-turn test
Chemical intoxication can affect motor control and balance. Asking drivers to walk in a straight line, turn around, and walk in a straight line again can expose signs of impaired physical abilities.
The walk-and-turn test looks at gait and balance. Drivers who cannot walk in a straight line or who stumble while turning may be at risk of arrest and prosecution.
2. The one-leg stand test
It is also common practice for police officers to have drivers they suspect of intoxication stand on one leg. Maintaining balance on one leg requires muscular control and focus. Of course, there are a host of other issues, ranging from naturally poor equilibrium to anxiety, that can affect a motorist’s performance on this test.
3. The horizontal gaze nystagmus test
Alcohol doesn’t just affect cognition and physical abilities. It can also impact subconscious physical activities as well.
Officers trying to determine if a driver is under the influence may ask them to follow their fingers or a small light without moving their head. The goal of this test is to watch for a muscle spasm when the eyes move laterally. That spasm exists regardless of circumstances, but it becomes much more visible in cases where people are under the influence of alcohol.
Field sobriety tests are not mandatory during a driving while intoxicated (DWI) traffic stop. They are also far from infallible. There are many reasons that people might fail field sobriety tests that have nothing to do with intoxication.
Learning more about how police officers gather evidence of impaired driving can be beneficial for those hoping to fight upcoming DWI charges. Motorists who can provide an alternate explanation for their field sobriety test results may be able to avoid a conviction when accused of drunk driving.