Police officers who suspect motorists of driving while intoxicated (DWI) offenses try to gather several different types of evidence to prove a crime occurred. They often follow people in traffic to record video footage of their questionable driving skills. They may request that the driver submit to a chemical test.
Often, chemical testing follows field sobriety testing. Police officers may ask drivers to exit their vehicles and perform a series of physical tasks. Field sobriety test results often become an important part of the state’s case when drivers face DWI charges. A motorist’s performance on tests may justify an officer’s decision to ask them to submit to a chemical test. Although the three standardized field sobriety tests have a basis in medical science, they may not actually be as accurate as people assume.
False positives are incredibly common
Federal traffic safety authorities have known for years that false positives are common during field sobriety testing. Researchers estimate that just under a quarter, or 23%, of horizontal gaze nystagmus test results are false positives. In other words, the test that watches for spasms and eye muscles only has a 77% accuracy rate.
The false positive rates for the walk-and-turn test and the one-leg stand test are even higher. There are a host of different medical issues that could lead to drivers performing poorly on those tests. In some cases, there may not even be an underlying medical condition.
Anxiety during a traffic stop can be enough to compromise an individual’s performance on the test. People who overanalyze their physical performance often become less fluid in their physical motions. Their nerves may ultimately increase their risk of failing the tests.
People who have failed field sobriety tests may still have opportunities to fight their pending DWI charges. Drivers can also avoid unnecessarily implicating themselves by knowing their rights. Drivers can typically decline requests for field sobriety testing without putting themselves at risk.
People responding to DWI allegations may need help planning a defense strategy. Raising questions about the outcome of field sobriety testing could help people establish a reasonable doubt about their chemical intoxication. A discussion with an attorney could help drivers plan the best response to their charges based on the circumstances leading to their arrest.