5 Reasons Why Prosecutors Shouldn't Be Able to Use Your FST Results Against You

October 2, 2026 | Posted In Drunk Driving

While police officers in New Jersey routinely use field sobriety tests (FSTs) to assess whether drivers are impaired, several issues can make drivers’ FST results unreliable. As a result, if you “failed” the FSTs, you will want to hire an experienced New Jersey DUI lawyer to make sure you do not face unnecessary consequences in court.

When the police pull you over on suspicion of driving under the influence (DUI), they can use several forms of evidence to establish probable cause for an arrest. One form of evidence police officers commonly use is drivers’ performance on the field sobriety tests (FSTs).

This is true even though the FSTs are notoriously unreliable.

While every case is unique, defendants facing DUI charges in New Jersey may have options to challenge the reliability of their FST results in court. If your FST results are unreliable, prosecutors should not be able to use them against you—and, if prosecutors do not have enough reliable evidence to prove your guilt beyond a reasonable doubt, you should not have to face the serious consequences of a DUI conviction.

What Are the Issues with the Field Sobriety Tests?

Field sobriety tests (FSTs) have several issues. These issues are well-documented, and each of these issues on its own can be enough to call a DUI defendant’s “failure” into question. With this in mind, the following are just a handful of examples of why prosecutors shouldn’t be able to use your FST results against you:

1. The Instructions for the FSTs Are Complicated

The instructions for the field sobriety tests are complicated. In order to pass the FSTs, you must know how to perform them correctly—and this is entirely dependent on your arresting officer clearly explaining what you need to do. If you did not clearly understand what you needed to do in order to pass—whether due to a poor explanation, a language barrier, or any other reason—this clearly is not justification for a DUI conviction.

2. The FSTs Must Be Administered According to Strict Protocols

Along with properly explaining the field sobriety tests, police officers must also properly administer the FSTs on the side of the road. Improper administration of the FSTs is common, and it can (and does) lead to unjustified arrests. This includes improper observation, interpretation, and reporting of drivers’ performance.

3. Road, Weather and Lighting Conditions Can Impact FST Performance

Road, weather, and lighting conditions can all impact drivers’ performance on the field sobriety tests. Gravel and wet pavement can cause drivers to slip or make it difficult for drivers to walk in a straight line; poor lighting can make drivers unsure of their footing, and the headlights of passing cars can compromise drivers’ vision—which in turn can compromise drivers’ ability to stand still or maintain a straight course. While these can all lead to FST “failures,” none justify a life-altering conviction.

4. Stress, Anxiety and Other Conditions Can Impact FST Performance

The stress and anxiety that result from being stopped by the police can impact drivers’ performance on the field sobriety tests. Other health conditions—from physical disabilities to cognitive disorders—can also impact drivers’ ability to pass the FSTs regardless of their level of impairment.

5. Shoes and Clothing Can Impact FST Performance

Even drivers’ shoes and clothing can negatively impact their ability to successfully perform the field sobriety tests during a DUI stop in New Jersey. High heels and shoes with slippery soles can make it difficult to balance on one leg or walk in a straight line heel-to-toe, and tight, baggy, or bulky clothes can also compromise drivers’ ability to perform the FSTs.   

FAQs: Challenging Your FST “Failure” in a New Jersey DUI Case

How can I raise reliability issues with my FST results in court?

While field sobriety test results can be unreliable for various reasons, as a DUI defendant in New Jersey, it is up to you to show that prosecutors should not be able to use your FST results against you. Seeking to keep your FST results out of court involves filing a pre-trial motion that explains precisely why your FST results should be deemed inadmissible.

Will successfully challenging my FST “failure” result in my New Jersey DUI case being dismissed?

Not necessarily—and this is critical. Even if prosecutors can’t use your FST results in your New Jersey DUI case, they may still have other evidence they can use to secure a conviction. This makes it critical to know all the evidence prosecutors have against you.

Are there also options for challenging my breathalyzer results in New Jersey?

Yes, you also have options for challenging your breathalyzer results in New Jersey. If you blew above the legal limit, this alone can be enough to establish guilt for a DUI, so it will be critical to determine if you have grounds to dispute your blood alcohol concentration (BAC) reading.

How Our Law Firm Can Help

If you are facing a DUI charge after failing the field sobriety tests during a traffic stop in New Jersey, we can help you fight to avoid a conviction by all means available. We can determine if you have grounds to dispute your FST “failure,” and we can also determine what other defenses we need to assert based on the facts of your case. The initial stages of a DUI case in New Jersey can move quickly, so we strongly recommend speaking with an experienced New Jersey DUI lawyer right away.

Speak with an Experienced New Jersey DUI Lawyer in Confidence

If you need to speak with an experienced New Jersey DUI lawyer, contact us promptly. To schedule a confidential initial consultation with an experienced lawyer at Helmer, Conlay & Kasselman, P.A., call us at 877-435-6371 or tell us how we can reach you online now.

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Don’t let your rights be jeopardized.