Even as little as thirty years ago, law enforcement officers were obtaining
probable cause to make DUI arrests by all sorts of means that were as
wildly inaccurate as they were varied. This prompted a massive study from
the National Highway Traffic Safety Administration into these tests in
order to find out which ones were the most accurate and how to make them
better to lead to fewer mistakes, fewer false arrests, and fewer accused
individuals being acquitted due to a mistake during the arrest process.
This study created three common field sobriety tests and the standards
by which they should be administered: the walk-and-turn test, the one-leg
stand test, and the horizontal gaze nystagmus. Today, these three tests
have been improved even further and are still relied upon as the most
accurate and useful tests for making arrests. However, there are still
mistakes made when issuing them, and that could still lead to a false arrest.
As a driver who may be forced to take one of these tests one day, here
is how each of them works as well as some of the mistakes that can lead
to a false positive and wrongful arrest.
Horizontal Gaze Nystagmus Test
The horizontal gaze nystagmus test is arguably the most widely-used test
due to its quick and easy nature, fairly high accuracy, and difficulty
to fool. While other field sobriety tests can be fooled, a horizontal
gaze nystagmus test is merely observing and looking for an involuntary
muscle spasm that those who are intoxicated lack the ability to control.
In this test, the administering officer holds up a pencil, small light,
or even just their finger at eye level in front of the accused individual
and then asks them to follow its motion without moving their head. When
the officer moves the target object slowly from side to side, they’ll
watch the suspect’s eyes for any twitching. This twitching comes
from an intoxicated brain losing the ability to fully control the muscles
that regulate eye movement. This generally leads to a pretty high accuracy
rate, making this one of the most trusted sobriety tests out there.
Walk & Turn Test
In the walk-and-turn test, the subject is asked to walk in a heel-to-toe
fashion down a straight line, before turning without lifting their feet
and then walking back. This test is designed to test someone’s ability
to focus on a mental task as well as a physical one—generally, the
officer will instruct someone on different things to do while also completing
this task, such as count the number of their steps and turn after completing
a particular number. Officers often look for signs that the brain is inhibited
in its function by forcing it to try to handle too much at once.
Sound difficult? It is, even for many sober individuals. Walking in a heel-to-toe
fashion is similar to walking on a balance beam, and that alone can test
someone’s ability to walk straight. Trying to focus on this walking
task while also counting your steps and then remembering to turn without
lifting your feet is a tough task to handle, and many people who are perfectly
sober actually fail this test. While it is a standardized test and accepted
as a method for obtaining probable cause, it’s still possible for
this test to yield a false positive and inaccurate results.
One Leg Stand Test
The one leg stand test is similar to the walk-and-turn in that it requires
you to split your mental focus between what you’re doing and a subsequent
mental task. In this test, an officer will usually instruct the test subject
to stand on one foot with their other foot pointed outward. Then once
they are in that position, they will ask the subject to count to 30 by
thousands (“one-one thousand, two-one thousand, three one-thousand…”).
Those who are intoxicated often have a lot of trouble holding their balance
while also remembering how to count in this manner.
Also similar to the walk-and-turn, the one leg stand does yield a substantial
number of inaccurate results as well, purely because of the difficulty
of the test. Standing on one foot in the required manner isn’t easy,
and for many people it takes substantial physical stamina to do so. As
a result, many people can’t hold out for the entire 30 seconds.
Some people forget to count by the one-thousands method. Results will
vary, but in any instance, the difficulty of the test may not have been
enough to allow an officer to develop any form of “reasonable suspicion”
and make a lawful arrest.