DUI Law: An Introduction To Field Sobriety Tests

Driving under the influence is a serious crime that can result in detrimental consequences if a person is convicted. For some reason, though, there were still well over 1.4 million drunk driving arrests in 2010 alone. Most of these convictions stem from the evidence gathered during field sobriety tests, but it’s important to know that none of these tests are an exact science. Those who fail a field sobriety test do still have defenses, but if they hope to be successful, they need to fully understand all of these tests and their limitations.

The Breathalyzer

Breathalyzers are one of the most recognized tools in the fight against drunk driving. They’re capable of testing the amount of alcohol in a person’s breath, and when this is known, the device can provide a person’s blood alcohol content (BAC) percentage. In all states, the legal limit for a person’s BAC is .08 percent, and any percentage over this amount can automatically result in an arrest.

It should be noted, however, that even these technologically advanced tools aren’t foolproof. Recently in Pennsylvania, for instance, hundreds of DUI cases were called into question when it was discovered that several breathalyzer machines hadn’t been properly calibrated. These devices can also produce false positives based on a person’s diet or whether they’ve recently used mouthwash or not. Because of this, no failed breathalyzer should be considered absolute evidence. Should you find yourself with a questionable DUI breathalyzer result, it’s important to consult with an experienced attorney, such as Katz & Phillips, to ensure you have been treated fairly.

Standardized Field Sobriety Tests

The National Highway Traffic and Safety Administration (NHTSA) has recognized three separate field sobriety tests as capable in establishing probable cause that a person is intoxicated. One of these tests is the “one-leg stand” test. This test occurs when an officer asks an individual to stand on one leg and count. Its reliability factor is around 65 percent.

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The “walk-and-turn” test is the test so easily remembered from old episodes of COPS when an individual basically has to tightrope walk along a line on the road. The “horizontal gaze nystagmus” is one that involves an officer moving a light in front of a person’s eyes and having them follow it without moving their head. These tests are usually sufficient to gauge a person’s intoxication, but certain factors in the suspect, such as disabilities or being overweight, can preclude these test results from being valid.

Non-Standardized Tests

The aforementioned standardized tests are the only ones approved by the NHTSA, and this means that any other field sobriety test can only be used as corroborating evidence. Tests where police ask drivers to recite the alphabet backwards or count backwards from a certain number have not been show to be a reliable indicator of intoxication. This means that if an officer only uses non-standardized field sobriety tests, they really haven’t established probable cause for an arrest.

Field sobriety tests are meant to help keep drunk drivers off of the road, but unfortunately, history has shown that innocent people have faced serious charges due to the periodic ineffectiveness of these tests. No one should ever look at the failure of a field sobriety test as an automatic conviction; this simply isn’t the case. With the right legal help, an individual can get the fair trial that they deserve even in the face of damning field evidence.


Kari Lloyd writes extensively on the legal issues associated with alcohol. If you wish to do further research on DUI issues and alcoholism, the Internet is a huge resource. Check with websites, such as DUI attorneys Katz & Phillips, as well as sites such as Alcoholics Anonymous.

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