Boise DUI Lawyers - Idaho Criminal Attorneys - Field Sobriety Tests

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Boise DUI Lawyers are always asked what the standard field sobriety tests are and if they are valid. The National Highway Traffic Safety Administration (NHTSA) developed three standardized tests to determine if there is probable cause to arrest an individual suspected of DUI. Standardizing the tests ensures consistency.

The three standardized tests are the Horizontal Gaze Nystagmus (HGN), Walk and Turn (WAT) and the One Leg Stand (OLS). These tests are used once an officer has probable cause to pull an individual over on suspicion of DUI. Once pulled over the officer administers the three standardized tests which provide the evidence for probable cause to make a DUI arrest and administer a breathalyzer test.

Boise DUI Lawyers may challenge probable cause for the initial pulling over as well as the probable cause based on the results of the field sobriety tests. Attorneys use challenges to probable cause to exclude evidence. Once the evidence is excluded the prosecuting attorney, the state's lawyer, may or may not have enough evidence to go forward to charge an individual with DUI.

The Horizontal Gaze Nystagmus works on the principle of eye muscle control. An individual who has not been drinking will show rapid eye jerking when the eyes are elevated to the maximum level. An individual who is intoxicated will show these jerking movements at less elevated levels as well as will have difficulty tracking with their eyes.

The Walk and Turn test requires an individual who is suspected of drinking and driving to walk nine steps from heel to toe and turn on one foot. The officer looks for clues as the suspect performs the tests. Such clues are inability to balance while listening to the directions, inability to walk heel to toe, inability to maintain walking in a straight line and failure to turn on one foot on the ninth step. As a Boise DUI lawyer I see people fail this test all the time, but I might suggest that even a non intoxicated individual may have difficulty performing this one.

The One Leg Stand test requires an individual who is suspected of drinking and driving to stand with one foot elevated about 6 inches above the ground and count by thousands for thirty seconds. As the suspect counts, one-thousand one, one-thousand two etc, the officer looks for wobbling, swaying, hopping or putting your foot down. Two or more of these indicators, according to the NHTSA, suggests the individual has an 83% chance of having over a .08 BAC. Again, as a Boise Criminal Lawyer I see individuals charged with DUI failing this test regularly. And, again, I would suggest that most people, especially the older you get, will fail this test.

DUI officers are trained to look at the three tests individually and as a whole. When looking at the results of all three tests they get what is known as a Combined Measures. With this they look at all three tests and evaluate the likelihood that the failures of the individual tests equal a DUI.

So, these are the standardized tests to establish probable cause for arrest on DUI. Are they effective? Can they be challenged?

According to the NHTSA, when comparing percentage of those actually found to have a BAC of greater than the legal limit from 1981 v. 1998, the accuracy of the tests due to training increased substantially. In 1981, when the legal limit for driving under the influence was .1, the accuracy for field sobriety tests were: HGN - 77%, WAT - 8% and the OLS - 65%. The Combined Measures resulted in an 81% accuracy arrest for DUI. In 1998, when the legal limit had been reduced to .08, the results were: HGN - 88%, WAT - 79%, and OLS - 83%. This translates into a Combined Measure accuracy of 91%.

In light of the NHTSA accuracy statistics can a DUI Lawyer still challenge the results. Absolutely. There are many factors which can go into failing a field sobriety test. Some examples of this are medical conditions such as vertigo or eye disease. Medications which have not legally impaired your ability to drive may make your balance on one leg questionable or cause you to have light sensitivity which could effect the HGN. DUI Lawyers will ask an individual charged with driving under the influence if they have any conditions which might impair their ability to take a standardized field sobriety test, but if you are pulled over on the suspicion of DUI and have a condition which might effect you performance, you should always let the officer know.

If you have been charged with DUI in Idaho and need to speak to a Boise DUI Lawyer, please call (208) 472-2383.