Field Sobriety Tests or FST’s are a physical means for an officer to gauge where or not a person is intoxicated. When the breathalyzer came into popularity, FSTs were used less frequently. While there are a number of Field sobriety tests out there, not all of them are standardized or approved for use by the national highway traffic safety administration (NHSTA) which can include the divided attention tests such as saying the alphabet backwards.

Of the accepted and standardized tests, there are three that are typically administered, which are the Horizontal Gaze Nystagmus (HGN), The turn and walk, and stand on leg. But how accurate are these tests in determining if a person is intoxicated.

Horizontal Gaze Nystagmus

The HGN is one of the most commonly performed of the field sobriety tests. Unfortunately, as an FST goes, the HGN is the most common for mistakes. One study has shown that up to 95% of officers perform the test incorrectly. The idea behind the HGN is the officer is checking for equal eye movement and pupil dilation.

One of the biggest issues facing this test is that the total number of passes, the distance of the stimulus (tip of pen, flashlight, finger) are all very specific to the test, even officers with the proper training can perform the test incorrectly, making the assessment that a person is intoxicated even if no alcohol is present. The other issue is that even with a dashboard camera, the jury cannot see the defendants eyes, so it comes down to the officers description and interpretation of the test.

Turn and Walk and Stand One Leg

Alcohol affects the central nervous system which in turn can affect things such as your sense of balance. Both the turn and walk and balancing on leg determine the balance of a potential defendant which can in turn be interpreted as a sign of intoxication. With the turn and walk, the defendant is told to take 9 toe to heel steps in a straight line, turn using a series of small steps, then take 9 toe to heel steps back. While there are eight different factors the officer is looking for to determine if the person is intoxicated, there are a myriad of factors that can throw the test off.

These factors include weather conditions such as rain or wind, a persons foot wear, and health conditions such as age, leg or back problems, or inner ear problems which can affect a persons ability to balance even when completely sober. These are also similar to the shortcomings of the Stand on One leg tests.

The Conclusion

Overall, these tests can be inaccurate due to several different environmental factors as well as being subject to the officers interpretation of these tests. This is one of the biggest reasons for FST’s being used less and chemical testing are being used more. Should you get pulled over and are suspected of driving under the influence, it is important to be cooperative and respectful to the officer.

However, what most people don’t know is that if you’re over 21, the legal drinking age, you have the right to refuse the officers requests for a FST. While you’re required to get out of the car if told to do so, refusing to participate in field sobriety tests cannot be held against you. A breathalyzer test, on the other hand, should be taken if required as you can be punished for refusing the test, even if you have no alcohol in your system. Just remember, above all, be courteous to the officer, especially if declining to participate in field sobriety tests.

+Andrew is one of the leading DUI and criminal defense attorneys in both the state of Maryland and the District of Columbia. He blogs about Maryland DUI law, has numerous videos on the subject and has been asked to appear on national television to offer his legal opinion on high-profile criminal cases.

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