DUI Field Sobriety Tests Are Unreliable

Extensive research indicates that the suite of field sobriety tests (FSTs) administered by law enforcement officers at traffic stops are inherently unreliable, even when administered in accordance with the standards required by the National Highway Traffic Safety Administration (NHTSA).

In fact, at the cut-off point of blood alcohol content (BAC of 0.08%), the data shows that standardized FSTs are only 72.2% accurate for determining intoxication.  To put it in simpler terms: more than 1-in-4 drivers who are administered FSTs are incorrectly assessed as intoxicated.

If you have been charged with a DUI on the basis of an FST administered during a traffic stop, you may be able to defend against such charges.  To succeed, your attorney must persuasively argue against FST reliability and demonstrate that the relevant law enforcement officers administered the tests in a non-standardized manner.

What Is a Field Sobriety Test?

An FST is – generally speaking – a test of coordination used by law enforcement officers to determine a person’s level of impairment and intoxication.  There are three types of standardized FSTs administered regularly at traffic stops.

Horizontal Gaze Nystagmus Test

The horizontal gaze nystagmus test (HGN) involves a law enforcement officer moving a point of interest (their finger or some other object) horizontally across your field of vision.  You are required to track the movement of the object with your eyes.  If your eyes begin to twitch or move in a staccato, jerky manner too soon before the object reaches your peripheral vision, then this is assumed to be an indication of intoxication.

In reality, however, these twitchy eye movements can be attributed to a number of other factors, such as natural nystagmus (some people are simply born with twitchier eyes), anxiety, tiredness, excitement, caffeine intake, among others.

Walk and Turn Test

The walk-and-turn test requires that you walk along a line indicated by the law enforcement officer, reach the end, then turn around and walk back.  The walk-and-turn test is particularly vulnerable to inaccurate testing, as the standards are unnecessarily strict at every step in the process.

When the officer is giving instructions on how to complete the test, you must stand in a very particular manner (think standing at attention in a military exercise) and wait for the law enforcement officer to give you to go ahead.  Afterwards, you must walk the line with each step touching your toes to the back of the opposite heel.  If you perform these tasks differently – even in a minor, insignificant way – then the officer may “fail” you.

One-Legged Stand Test

The one-legged stand test is not just difficult for intoxicated persons – it is physically demanding for many sober people too!  During administration of the test, you will be required to stand on one leg and count until the law enforcement officer asks you to stop counting.  More than one deviation from a perfect test (such as having to hop to maintain balance, or moving your arms to help maintain your balance) will count as a failure.

Other Tests

There are other non-standardized FSTs such as the Alphabet Recital test, but in the wake of the NHTSA’s development of standardized FSTs, they are no longer commonly used.  If a law enforcement officer administers a non-standardized FST as their sole assessment of intoxication, there is a good chance that those results will be deemed invalid.

Why Are Field Sobriety Tests Unreliable?

There are primarily two reasons why FSTs tend to be unreliable: 1) law enforcement officers regularly fail to administer the tests in accordance with prevailing standards; and 2) there are often confounding factors that “muddy up” the data.

Failure to Administer Correctly

The failure of a law enforcement officer to correctly administer an FST in accordance with NHTSA standards is unfortunately common.  An officer may fail to adhere to standards at all phases of administration, from the instructional phase to the testing phase.  Even if an officer has administered an FST “by the book”, there is a chance that he or she has made a mistake at some point in the process.

For example, an officer may mistakenly perceive that you did not touch heel-to-toe during your walk-and-turn test, when you actually did touch them together.  An officer may also become distracted and take an unreasonably long time to tell you to stop counting during the one-legged test.  This can result in you getting tired, wobbling, and being forced to hop or move your arms to reassert your balance (thus failing the test).

Confounding Factors

There are several confounding factors that can affect the outcome of an FST, including but not limited to age, natural physical ability, caffeine intake, anxiety, and tiredness.  Even a correctly administered, standardized FST may not adequately account for these factors.

For example, suppose that a driver is overweight and is asked to perform the one-legged stand test at a traffic stop.  Due to his weight, the driver is unable to stand on one leg for very long.  He drops his leg to avoid falling over.  The officer thereafter “fails” the driver.  The confounding variable of the driver’s weight no doubt affected the results of the test.

Whether a person is capable of performing the tasks required of them during an FST is not an exclusive indication of their impairment or their level of intoxication.  A one-size-fits-all approach is simply not good enough when it comes to charging a driver with a DUI on the basis of such results, and the statistics prove it.

FSTs are inherently unreliable.  If you or someone you love has been charged with a DUI after the administration of an FST by a law enforcement officer, you may be able to fight the charge. Call (941) 900-3100 as soon as possible to speak with experienced Sarasota DUI attorneys today.

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