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What are the field sobriety tests in Missouri?

In recent history, law enforcement has acquired more sophisticated ways of testing whether or not a driver is under the influence. Specifically, breathalyzer tests can almost instantly determine the level of alcohol in a person’s blood.

However, the field tests that predate this technology are still used by officers today — especially when a driver is suspected of being under the influence of a prescription, over-the-counter or illegal drug. Here are the tests you could be asked to perform in Missouri.

1. The walk and turn

This test is one of a few that the state of Missouri recognizes as a legitimate indicator of intoxication. To conduct this test, an officer will ask the driver to step out of his or her vehicle and take nine heel-to-toe steps in a straight line. The driver must then turn on one foot and return, taking nine more heel-to-toe steps straight back to the original position.

Law enforcement officials will observe whether the person is able to remain balanced, walk straight and respond to orders in a timely fashion. The driver can fail the test by starting too soon, stopping, using his or her arms to balance, stepping off the straight line, taking an inaccurate amount of steps, failing to touch heel to toe or failing the turn.

2. The one-leg stand

The one-leg stand test is sometimes criticized, but still currently recognized as a standardized field sobriety test in Missouri. To pass this test, drivers must raise one foot up 6 inches off the ground and count by thousands until the officer instructs the person to stop. This should usually last about 30 seconds, or 30 one-thousands.

A police officer may fail a person who cannot keep their arms at their sides, hops, wobbles, counts inaccurately, falls or puts his or her foot down.

3. The horizontal gaze nystagmus

The horizontal gaze nystagmus test is also sometimes referred to as the pen or eye test. To give the test, an officer instructs the driver to use their eyes to follow a stimulus, often a pen or finger, from left to right.

Many people hold the misconception that this tests whether the driver can maintain eye contact with the stimulus. In fact, the officer is actually checking for nystagmus, an involuntary twitching of the eye. If the pupil begins jerking at or before it is turned to a 45-degree angle, the person likely has a high BAC.

Should I consent to a sobriety test?

It’s important to understand your rights when it comes to taking a field sobriety test and a chemical sobriety test.

Refusing to participate in a field sobriety test is within your rights and will not result in an automatic penalty. However, participating in a field sobriety test and passing can help prove that you were of sound mind and body to operate your vehicle safely.

If you are asked to take a chemical test, meaning a breath, blood or urine test, your consent to be tested is already implied. Under the implied consent law, refusing to take a chemical DUI test subjects you to automatic penalties, including the revocation of your license for one year — whether you were intoxicated or not.

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