Types of Sobriety Tests and Why They’re Unreliable

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Intoxication by alcohol can be detected in different ways. One is through quantitative measurements using advanced equipment. For example, the breathalyzer test can detect blood alcohol concentration. Motorists blow into the device and the results come out almost immediately.

They can be arrested on the spot if they exceed the legal limit. However, it is possible for people to stay under the limit and still show signs of intoxication. Alcohol has varying levels of impact on those who consume it, after all. It is for this reason that law enforcers use field sobriety tests to check for impaired driving.

Horizontal Gaze Nystagmus Test

The countless deaths and injuries that have resulted from drunk driving have inspired numerous studies on the matter. Researchers have tried to find ways to reduce the dangers by helping law enforcers spot impaired individuals in the field.

The horizontal gaze nystagmus test or HGN is among the easiest to perform. It usually comes first in the battery of tests that officers administer. They simply need to observe the subject for involuntary eye movement along the horizontal axis. Various cues point to the likelihood of a BAC that is higher than 0.08 percent. The more cues observed, the higher the BAC.

Some experts have questioned the accuracy of this test. They say that its development was rushed such that it bypassed rigid scientific review. It became a standard police procedure not because it had a good foundation but because it was endorsed by the relevant federal agency. Those who have taken the time to evaluate the research behind it came out unimpressed with the methods used.  

Walk and Turn Test

This straightforward sobriety test examines the ability of the driver to follow directions, walk in a straight line, and keep their balance throughout the process. It hinges on the assumption that a normal sober person should be able to ace it, and that only someone who has consumed drugs or alcohol could commit a blunder with such a simple task. The subject must take about nine steps forward right ahead, then turn and walk in the opposite direction until he returns to the starting point. The task must be completed without wobbling, stopping, using arms, toppling, or taking an incorrect number of steps.

The theory is that failures and blunders point to impairment stemming from excessive substance ingestion. Critics say that this is not always true and that the test is unreliable. They point out that the observations are subjective. Police officers may not view a test in the same way because personal bias can get in the way. People tend to have their own opinions on what sobriety and impairment mean. The design of the test is also said to be skewed towards a failed outcome.  

One Leg Stand Test

This test will check whether the motorist can obey instructions and maintain balance for a set amount of time. Officers will ask the subject to stand on one foot with the other being off the ground by a good six inches. The hands must be kept to the sides. This pose must be held for thirty seconds with the subject counting the time out loud. Indicators of impairment include difficulties retaining balance, putting the foot down prematurely, using the arms to minimize side-to-side movement, and similar observations.  

Like the walk and turn test, critics say that this is designed to induce failures. Even a sober person can fail this test because of the physical difficulty of the task. Not everyone can maintain perfect balance for that period while resting on one foot. It takes a certain level of fitness and athleticism to do so. Older or frail persons might be falsely accused of DWI not because they are actually drunk but because they are not capable of completing the task even on their best day.

Those who feel that they were unfairly accused of driving impaired should immediately contact a DWI defense lawyer who can help them disprove the allegations and point out the weakness of these tests.