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3 Important Differences Between Breath Tests and Field Sobriety Tests in New Jersey DUI Cases

June 1, 2022 | Posted In Drunk Driving

When the police pull you over on suspicion of drunk driving in New Jersey, they can ask you to submit to two different types of tests: the breath test (or “breathalyzer”) and the field sobriety tests (or “FSTs”). While it might not seem like there would be any major differences between taking the breathalyzer and taking the FSTs, there are actually several key differences—and these differences can drastically impact your defense. Keep reading to learn more from an experienced New Jersey DUI lawyer.

How Are Breath Tests and Field Sobriety Tests Different (and Why Does It Matter)?

Before we get into the differences, we should cover the ways in which the breath test and field sobriety tests are similar. First and foremost, New Jersey prosecutors can use both as evidence against you. If you blew above the legal limit or failed the FSTs, this is an issue you will need to address head-on when building your defense strategy.

Second, while the breath and field sobriety tests can be used as evidence in court, they both have significant shortcomings. From calibration issues with breathalyzers to issues with how arresting officers explain the FSTs, there are numerous issues that can provide strong defenses even if you “failed” one of these tests. So, regardless of what happened during your DUI stop, you should not make any assumptions but instead make informed decisions based on your New Jersey DUI lawyer’s advice.

Those are the key similarities. Now, on to the differences. Here are three important differences between breath tests and field sobriety tests in New Jersey DUI cases:

1. The Breath Test is Mandatory, But the Field Sobriety Tests are Not

Under New Jersey law, you are required to take a breath test during a DUI stop if the police officer asks you to do so. This is based on New Jersey’s “implied consent” law, which basically states that by driving on New Jersey’s public roads, you automatically consent to a breath test if the police pull you over on suspicion of DUI.

The police cannot physically force you to take a breath test, but if you refuse, you can be charged with an implied consent law violation, which is also known as a DUI refusal. If you get charged with a DUI refusal, you can be convicted and sentenced for violating New Jersey’s implied consent law even if you weren’t drunk when the police pulled you over.

However, New Jersey’s implied consent law does not apply to the field sobriety tests. In other words, you can refuse to take the FSTs and not face a DUI refusal charge. Unfortunately, the police don’t always (or often) present the field sobriety tests as being optional, and, as a result, many people feel compelled to take them even though they are not legally required to do so. If you mistakenly believed that you were required to take the FSTs, this does not entitle you to have your test results kept out of court.

2. The Breath Test has Objective Standards, While the Field Sobriety Tests Don’t

The breath test measures your blood alcohol concentration (BAC). This is an objective measurement. If you are 21 or older and your BAC is 0.08 percent or above, you are “over the legal limit”—and you can expect to be arrested and charged with DUI. If your BAC is 0.10 percent or above, you can face enhanced penalties in your DUI case.

New Jersey has other BAC standards as well. For example, drivers who are under 21 are subject to New Jersey’s “zero tolerance” law, and a BAC of just 0.01 percent can be enough to trigger an arrest. If you hold a commercial driver’s license (CDL), you can be convicted of DUI for driving with a BAC of 0.04 percent or above.

While the breath test has objective standards, the field sobriety tests do not. Instead, whether you “pass” or “fail” the FSTs is up to the arresting officer’s interpretation of your performance on the tests. While these tests are standardized—meaning that there are specific protocols and indicators the police are supposed to observe—experience shows that DUI defendants’ FST “results” are often flawed.

3. The Defenses for a High BAC and a Failed Field Sobriety Test are Very Different

As we mentioned above, the breath test and the field sobriety tests each have flaws. Exposing these flaws can be a highly effective defense strategy in New Jersey DUI cases. But, the flaws with the breath test and the FSTs are very different, and understanding these differences is key to building a successful defense.

Some examples of issues that can invalidate breath test readings (BAC results) in DUI cases include:

  • Failure to properly calibrate the breathalyzer device
  • Failure to adequately clean or maintain the breathalyzer device
  • Failure to maintain adequate documentation of the breathalyzer device’s calibration, cleaning or maintenance
  • Improper administration of the breathalyzer
  • Consuming breath mints, foods, or medicines that can cause “false positives”
  • Having certain medical conditions that can cause a “false positive”

Some examples of issues that can invalidate field sobriety test results in DUI cases include:

  • Failure to properly explain any one of the three FSTs (the walk-and-turn test, one-leg stand test or horizontal gaze nystagmus test)
  • Failure to carefully observe the DUI suspect throughout the performance of the test
  • Misinterpretation of the DUI suspect’s performance on the FSTs
  • Having acquired nystagmus or another medical condition that affects your eye movement
  • Having a medical condition that affects your balance
  • Wearing unstable shoes or being on unstable ground

Fight Your Drunk Driving Case with the Help of an Experienced New Jersey DUI Lawyer

If you are facing a DUI charge in New Jersey and you failed the breath test or field sobriety tests (or both), you should discuss your case with an experienced New Jersey DUI lawyer promptly. Call 877-435-6371 or contact us online to schedule an initial consultation as soon as possible.


Over 20 attorneys at HCK have extensive experience in defending DUI cases as they were former assistant prosecutors and/or police officers for a combined total of over 600 years of law enforcement experience. You can find out more about them on our site, and you can call Managing Partner Ron Helmer on his cell phone at 609 685-0665.

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