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Loudoun DUI Field Sobriety Tests

Field sobriety tests are a battery of tests that law enforcement officers use to prove that you’re impaired and are not able to operate a motor vehicle safely. These tests were derived years ago by the National Highway Traffic Safety Administration (NHTSA). They made a series of studies conducted in a controlled environment. They’re not always accurate to modern roadways and driving conditions. The three most common field sobriety tests are the horizontal gaze nystagmus test (HGN), the nine step walk and turn, and the one-leg stand test. Below, a DUI lawyer in Loudoun County talks more about these tests and how they are typically used by law enforcement.

Horizontal Gaze Nystagmus

This is a test to look for nystagmus or involuntary jerking in the eyes when they’re resting. When performed with the expert knowledge of ophthalmologists, the presence of nystagmus at maximum horizontal deviation is a sign of alcohol impairment.

To do the horizontal gaze nystagmus test, the officer uses a stimulus—typically a pen, or their finger. The stimulus is positioned approximately six inches from a person’s eyes and then slowly moved to the left and back to the right to a 45-degree angle to look for nystagmus and lack of smooth tracking.

There is another test within the HGN test, where the officer is looking for whether or not the other person follows directions. It is possible that you may perform well but not necessarily pass the test, because you did not follow the directions as stated.

Often the directions are stated very quickly and in a somewhat confusing manner. For example, for the HGN test, the officer will request that you stand perfectly still without moving your head and move only your eyes. However, they may administer the test in such a manner that it’s hard to follow with just your eyes and if your head involuntarily follows that’ll be used as a clue of impairment.

Walk and Turn Test

The nine step walk and turn test is the old “walk-the-line” test that people have seen in driver’s ed videos.

The nine step walk and turn is a very specific, divided attention test that is very difficult to perform correctly, even under optimum conditions and even after having consumed no alcohol at all. One of the reasons that this test is so difficult to perform is the officer requests that the driver stand in a certain position called the “starting position” while receiving directions prior to beginning to test.

This can include placing one foot in front of the other in a heel-to-toe position with your arms at your side. Depending on the size of one’s leg, the size of one’s feet, and the type of footwear, this can be quite uncomfortable.

Then the person will be asked to walk an actual or imaginary line for nine steps—stepping heel to toe while counting out loud. Once they’ve reached the ninth step, they’ll be instructed on how to turn and return back nine steps to where they came, again touching heel to toe with their arms at their sides.

The officer is looking for many things from the nine step walk and turn test, including whether or not a heel-to-toe touch occurred at every step, whether or not the correct number of steps occurred, whether or not the person counted out loud, and whether or not they stopped and started at  when instructed.

One-Leg Stand Test


For the one-leg stand test, this is a sobriety test where you will see officers looking for whether or not the person is following directions just as much as they’re looking for the physical performance.

For the one-leg stand test, the officer will instruct the person to look at their toe, lift the foot of their choice up to six inches off the ground, and with their arms at their sides count to 30. This test only should last 30 seconds and the officer will say stop if the person has not reached 30 seconds without performing the test correctly.

In addition, the officer will not instruct the person on the secret to performing this test correctly, which is to load their weight on to one foot with a slight bend in the knee and flex their backside. The officer will use this secret when demonstrating the test, however the officer will never tell the person asked to perform the test to do it.

Therefore, even people that perform the test without impairment will often still suffer from balance issues if performing the test correctly. Again, this is a divided attention test and the officer is looking for whether or not the directions are followed as much as he is looking at the physical performance. Often you see these tests administered in a certain way.

What Is The Weight Of Field Sobriety Tests At A DUI Trial?

Certain tests are weighed more heavily than others. The performance of a nine step walk and turn, one-leg stand test, other field sobriety tests, such as the finger dexterity test are viewed much more strongly than the HGN test, which is often discredited or not allowed depending on the evidentiary basis for the test.

Do Loudoun County Officers Use Field Sobriety Tests Differently?

Different law enforcement officers use different field sobriety tests in their own personal way. Certain law enforcement officers only use the standardized tests—HGN, nine step walk and turn, and the one-leg stand.

Other law enforcement officers throw in additional tests. This is especially true if a person has a physical limitation and is unable to perform the field tests. These additional tests may include finger dexterity, where they’re touching the fingertip while counting backwards or forward or saying the alphabet backwards or forward.

Can You Refuse Field Sobriety Tests?

Yes, you can and absolutely should refuse to perform field sobriety test at any time.

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