Flaws in DUI Tests

If you have been pulled over under suspicion that you are driving under the influence (DUI), you will likely be administered a field sobriety test to assess your level of intoxication. There are three main types of field sobriety tests, each of which comes along with its unique flaws. Unsurprisingly, the system is not perfect and leaves much room for error. However, this also provides individuals accused of a DUI with opportunity to prove innocence. Furthermore, let’s explore the 3 main types of field sobriety tests and how the tests are often flawed.

3 Types of Field Sobriety Tests

As discussed, there are three main types of field sobriety tests that you may be administered if you are pulled over for a DUI. Here, we will analyze each of them.

  • Horizontal gaze nystagmus (HGN): The HGN test assesses the responsiveness of your eyes. HGN can be used to describe the involuntary jerking movement of one’s eyes. To conduct this test, a police officer will hold an object in front of your face and you will be asked to track the movement of it with only your eyes. If you have very exaggerated jerking reactions, instead of smooth transitions, this may be indicative that you are under the influence. 
  • One-leg stand test: The one-leg stand test is used to test how well you are able to keep your balance. You will be asked to stand on one leg for a period of approximately 30 seconds, of which you are not allowed to put down your other leg and should avoid swaying. If you are intoxicated, you will likely be unable to balance on one leg due to your impaired motor skills.  
  • Walk-and-turn test: The walk-and-turn test is another type of field sobriety test that may be used after you have been pulled over. This test is used to determine how well you are able to maintain your balance and follow directions. To complete the test, you must walk heel-to-toe, taking nine steps in a straight line. Then, you must turn around and trace your steps in the same manner. 


Prescription medications have the potential to interfere with DUI tests, as many of them have side effects that can influence an individual in more ways than one. Depressants, anxiety medicines, antihistamines, painkillers, muscle relaxants, and asthma medications are all examples of medications that may lead to a false positive field sobriety test. For example, if you are taking a muscle relaxant, such as Flexeril, it may cause your muscles to become a little too loose, which can affect your ability to control and contract them to perform the field sobriety tests.

Pre-Existing Medical Conditions

Pre-existing medical conditions can also play a role in the accuracy of DUI tests. For example, let’s say that you have extremely weak ankles as a result of a serious injury that occurred years ago. Due to this weakness, you are unable to stand on one leg, as doing so is too demanding on your ankles. Therefore, if you are administered a one-leg stand test and you are unable to successfully pass it, this could be largely attributed to your ankle injury and not your level of intoxication. Another example would be if you had a pre-existing eye condition, such as a lazy eye that may inhibit your ability to properly perform the HGN test. 

Weather Conditions

Weather conditions can also influence the accuracy of your field sobriety test. For example, if the roads are wet because it rained the night before, this may make it far more difficult to maintain your balance or walk in a straight line, if performing the one-leg stand or walk-and-turn test. These external weather factors should absolutely be taken into account when determining test performance. 


Field sobriety tests are very subjective in nature, meaning that the way in which you are assessed for your performance can be largely up to the interpretation of the officer. This creates a great amount of inconsistency in how intoxication is detected and can also unfortunately lead to discrimination.

Legal Defense 

As we have learned, DUI field sobriety tests can be highly flawed and can lead to false accusations. If you believe that you have been wrongly charged with a DUI, an Indianapolis criminal defense attorney can create a convincing argument on your behalf, using the inevitable flaws in the testing system as evidence. A DUI can have life-lasting implications, therefore do not hesitate to seek legal counsel in order to get your charge lifted. 

Author: Brandon Park