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How Accurate Are Field Sobriety Tests?

Are Field Sobriety Tests Truly Accurate?

Field sobriety tests are a combination of different tests used to assess if a vehicle driver is under the influence of any substance. These tests have been around a long time and are still in practice today; however, field sobriety tests, or standardized field sobriety tests, aren’t always exactly accurate. In this guide, we’ll explain how. 


What are Field Sobriety Tests?

The purpose of these tests is to assess the cognitive function and physical impairments in a person driving any type of vehicle. Standardized field sobriety tests are administered by a trained officer who, instead of using a device, judges the physical response of a driver to the tests in order to conclude if he or she is under the influence of any intoxicant. 

Used mostly in the United States, FSTs have resulted in many sober drivers failing them because of the unpredictability of the tests. In Field Sobriety Tests, the officer-in-charge is the ultimate decision-maker and has the power to determine if the subject is impaired or not, meaning there is no pass or fail metric. Instead, the officer uses his or her observation to determine if the driver is under the influence of a substance or not.

What to Expect During a Field Sobriety Test 

Made up of three different cognitive and physical impairment tests, Field Sobriety Tests have been used for over four decades to determine the status of a driver’s intoxication.

These tests serve as probable for a DUI arrest and conviction; some states even allow FSTs to be used as evidence in a trial. 

If a subject ends up failing FSTs, they are asked to take a breath test or some other chemical test to further confirm if they are intoxicated or not.

The three tests that make up Field Sobriety Tests are Horizontal Gaze Nystagmus, Walk-And-Turn Test, and One-Leg Stand Test. 

Horizontal Gaze Nystagmus

In a Horizontal gaze nystagmus test, the movement of the eye is assessed. The officer looks directly into the eye of the driver to see if there is any involuntary movement that might be the result of intoxication. 

The subject is asked to follow the movement of a dynamic object like a flashlight, from one side to the other, during which the movement of the eyeball is observed closely by the officer.

If there is any more than the normal jerking of the eye, the subject is asked to take the next test. In HGN tests, head movement is also observed closely.

The Walk-And-Turn Test

The Walk-And-Turn Test involves a number of steps that are used to assess the mental and physical condition of the driver. The drivers are instructed to stand heel-to-toe while the officer gives instructions and explains what they are supposed to do. Most of the time, the instructions involve taking nine steps forward, turning on one foot, and taking nine steps backward. While the instructions are being given, the movement of the subject is closely followed; if he or she can’t keep their balance or does not follow the instructions attentively, it draws more suspicion. 

After the instructions are given, the subject is asked to undertake the test, during which their movement is observed, and several factors are assessed to see if there are any signs of intoxication. 

One-Leg Stand

In the One-Leg Stand test, the officer asks the driver to stand on one leg and count from one thousand one onwards. The person has to stay in this position for almost 30 seconds, while the person is standing on one leg, the officer searches for several DUI indicators.

If the driver uses their hands to balance themselves or ends up putting the foot down or sways to the side while balancing, the officer can deem them to be under the influence of a substance. 

How Accurate are Field Sobriety Tests?

There is a lot of debate over the accuracy of FSTs and many experts think they are not accurate enough to be used as primary tests for drunk driving or DUI. As per several outlets and sources, it has been observed that many people can fail Field Sobriety Tests even if they are sober. 

The accuracy rate of these tests is also not the best. According to the National Highway Traffic Safety Administration, all three Standardized Field Sobriety Tests, when used together, have an accuracy rate of 82%. This rate becomes even lower when the tests are used individually.

It has been found that the horizontal gaze nystagmus test on its own is only accurate 77% of the time, which is still a lot in comparison to the accuracy rates of the other two tests. The walk-and-turn test is only correct 68% of the time, and the one-leg stand has the lowest accuracy rate of all the three tests, with only 65%.

What are some Problems with Field Sobriety Tests?

When carried out in the real world there are several problems with field sobriety tests. Numerous reasons can affect the outcome of these results and can end up costing an innocent person their driving license, among other more severe consequences. 

Studies have shown that there is considerable room for improvement when it comes to implementation of field sobriety testing. 

Human Error

The first problem with FSTs is the human error involved. The police officers administering the tests are also human and can make mistakes. In fact, the mistakes made by officers are the leading reason for the failure of these tests. 


Among other factors, distractions can also make the driver lose their focus. A vehicle passing by can cause someone to lose their balance or deviate their attention during the walk-and-turn and one-leg stand tests. 

Environmental Factors

Environmental factors also have a role to play when it comes to the accuracy of Field Sobriety Tests. Fast blowing winds or lightning strikes can make the driver lose focus and balance, which can cause them to fail their tests. 

Existing Issues

If someone already suffers from issues like ADHD, among other problems, Field Sobriety Tests might be hard for them to undertake. 

Apart from these, there are several other factors that can affect the outcome of SFSTs.

What Do I do if I Fail a Field Sobriety Test and get a DUI?

Driving under influence is one of the most prevalent issues when it comes to traffic. Thousands of people are convicted of DUI each year and end up dealing with major consequences.

Drunk driving is the leading cause of roadside accidents in the world, which goes to show how detrimental a DUI can be to your career and overall life.

In order to get over DUI, it is best to take DUI and Alcohol Education courses. Cornerstone Healing Center excels in providing the best DUI education classes in the United States, which not only educate you on the consequences of driving under influence but also show you how to overcome this problem.

Cornerstone Healing offers online DUI classes, which make it even easier to seek help.

If you have a loved one who is at risk of getting a DUI violation, give us a call and let’s discuss the situation. 


[1] Field Sobriety Testing Accuracy Study



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