The Standard Field Sobriety Test

Posted by James Ferguson | Oct 01, 2018 | 0 Comments

The Standard Field Sobriety Test or FST is a battery of three tests performed during a traffic stop to determine driver impairment. The three tests that encompass the FST are the horizontal gaze nystagmus, the walk-and-turn, and the one-leg stand. The FST was developed in the 1970s as a scientifically validated means of determining whether an individual is driving under the influence. The FST is admissible as evidence in court in most states including Mississippi.

Are Field Sobriety Tests Reliable?
To answer this question of whether FSTs are reliable, it is imperative to analyze the beginnings of field sobriety tests. In the late 1970s, prominent organizations with an interest in preventing highway casualties and intoxicated driving convened. They wanted to determine the most accurate sobriety test to administer to suspected DUI offenders. To make this determination, officers gathered to observe various tests to determine the blood alcohol content (BAC) of the subject and whether it was above the legal limit. After making their observations, the officers settled on three tests as the most accurate and reliable at determining illegal levels of alcohol. Nevertheless, these tests are not error free. In actuality, it was discovered that each test included a margin of error. The horizontal gaze nystagmus test is 77% accurate; the walk and turn is 68% accurate and the one-leg stand is 65% accurate. These tests combined have an overall accuracy rate of 82%. Scientists have disputed the accuracy of the tests and whether they support the reliability of a standardized test.  

Challenging a Field Sobriety Test
Individuals charged with a DUI assume that failing an FST proves guilt. That is false. Prosecutors do frequently use evidence of FST failure to support a guilty ruling or to produce a guilty plea. The FSTs are not dispositive of one's guilt. This is where it is important to hire an experienced attorney who will defend against your FST failure. Depending on the circumstances surrounding the testing, a DUI defendant can make a challenge to the admissibility of the failure and have it thrown out of the record. Other circumstances can produce a failure outside of the consumption of alcohol including unknown side effects associated with legal prescription drugs and illness.

What to do When Faced with a Field Sobriety Test
DUI suspects are not required by law to agree to perform the FST when it is offered. Law enforcement officers will usually make this offer on multiple occasions during the encounter. Individuals in this situation have to remember that the law enforcement officers have other means of determining alcohol intoxication including the use of a blood test or a Breathalyzer. FSTs are inherently difficult to perform and they can be confusing. The more evidence of your intoxication the prosecution has, the stronger the case against a defendant. The best practice when faced with an FST is to submit to a more reliable test (if the individual is so inclined). Still, the suspected DUI offender is not required by law to submit to any form of testing, whether it is a blood test or a Breathalyzer. However, the suspected offender should be aware of the penalties that may follow from refusing to take a test.

Your DUI Attorney
Attorney James Robert Ferguson is an experienced DUI attorney with years of experience defending DUI cases. Driving Under the Influence is a serious crime. If you have been charged with DUI, you need an experienced attorney. Attorney Ferguson understands that the stakes are high and the importance of putting the charge behind you. Call us now for a consultation.

See related blog posts:
I Have Not Been Drinking - I Can Juggle!
Are Sobriety Checkpoints Legal in Mississippi?

About the Author

James Ferguson

I was born and raised in Memphis, Tennessee. During college, I studied at East Tennessee State University, where I received a Bachelor's in Criminal Justice, which I then followed up with a Master's in Criminology from the University of Memphis. Before beginning my legal career, I worked as a Project Coordinator at the University of Memphis, where I assisted in training law enforcement officers in the Memphis Model of Crisis Intervention Training. The purpose of the project was to provide officers with the tools to deal with citizens in a state of mental crisis. I then went on to study law at the Mississippi College School of Law in Jackson. During law school, I clerked with Victor W. Carmody, Jr., the lawyer who wrote the book on DUI law in Mississippi. I am currently licensed to practice law in both Tennessee and Mississippi, and spend a majority of my time traveling the highways and biways of Mississippi defending those who have been charged with a DUI.


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