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How Accurate are Field Sobriety Tests?

If you are stopped by a law enforcement officer who suspects you may be intoxicated while driving, he or she will likely ask you to perform a seemingly simple task, such as standing on one foot or following the officer’s finger without moving your head. These tasks have a purpose: They’re designed to show signs of intoxication that can help establish probable cause and justify the arrest of someone the officer suspects is driving while under the influence. However, there’s a kicker: Many people don’t realize how incredibly inaccurate these tests really are.

The Human Condition

Field sobriety tests are heavily dependent on an officer using good and impartial judgment. However, any test that requires judgment is prone to “confirmation bias,” which is a natural tendency to look for evidence that supports a pre-existing assumption or desired outcome. In other words, if an officer believes you’re intoxicated, he is far more likely to see a positive result in a field sobriety test than a negative one, simply because that’s what he is looking for to confirm his suspicions.

There is inherent unreliability in the tests, as well. Today, law enforcement uses three “standardized” field sobriety tests: the walk-and-turn, the one-leg stand, and the horizontal gaze nystagmus test. Even after heavy refinement and extensive testing, the most reliable of these tests, the horizontal gaze nystagmus, still led to false positives and unlawful arrests at a rate of nearly 30 percent.

The Effect on Your Case

With further refinement, the tests have become more accurate, especially when multiple tests are used. However, accuracy is still only about 90 percent, which means one out of every 10 people is falsely arrested. This is an important finding, because proving that the officer who arrested you never established probable cause is a valid defense against DUI charges.

Of course, providing such proof requires a thorough knowledge of the law and an ability to review all available evidence. Therefore, is is strongly advised that you don’t attempt to use this defense on your own without first speaking to a Riverside DUI attorney.

If you have been arrested and charged with DUI, call Blumenthal & Moore today at (951) 682-5110to request a no-charge case evaluation and start reviewing your options to fight back against the accusations.

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