Passed a Breathalyzer Test? You Can Still Be Convicted of a DUI Offense

If you're charged with drunk driving, the results of a Breathalyzer test are just one form of evidence that can be used in court. Passing the test doesn't guarantee acquittal. Similarly, failing a breath analysis test doesn't guarantee a conviction.

This article discusses the role blood alcohol content (BAC) tests play in a DUI case — particularly the Breathalyzer test. First, the article addresses evidence in a DUI case. Then it looks at BAC testing and implied consent. Next, there's a discussion about how Breathalyzers work. Finally, the article addresses defenses to field sobriety tests. FindLaw's Sobriety Tests section contains additional articles and resources to help you better understand the law.

Evidence in a DUI Case

According to the National Highway Traffic Safety Administration, there are 20 identifiable symptoms that may indicate a person is driving impaired. These driving patterns give police probable cause to stop a vehicle and investigate for driving under the influence (DUI). Sworn testimony from an arresting officer and video footage of your motor vehicle before the stop may not be compelling evidence on their own, but such evidence may serve as the basis for a case.

Statements from the driver are also admissible evidence. Unless you've had no alcohol at all, if you're asked how many drinks you've consumed, it's wise to respectfully decline to answer questions until you speak to an attorney. That's your right.

Admitting to having any number of drinks will be included in the police report. That evidence can be used against you in court. Also, if you're excessively hostile, your demeanor will weigh against you in court.

BAC Testing and Implied Consent

If you're asked to submit to a BAC test as a driver, you're required to comply under implied consent laws. By driving, you implicitly consent to chemical testing to determine impairment.

Suppose you refuse to submit to any chemical test, whether it's a breath test, blood test, or urinalysis. Your refusal will usually be admitted in court as "consciousness of guilt." In most states, your refusal will also typically result in an automatic suspension of your driving privileges.

Failing a chemical test with a BAC of 0.08% or higher will result in immediate arrest. Additionally, state laws usually allow a driver to be charged with DUI for a BAC between 0.05% and 0.07% if other evidence shows impairment.

How Breathalyzers Work and Sometimes Fail

A Breathalyzer (the brand name of an early breath-testing device) measures alcohol vapor in your breath. This device is the most commonly used chemical test for DUI suspects. However, the equipment has several drawbacks. The results aren't generally enough to convict you without other evidence supporting intoxication.

A Breathalyzer assumes the entire volume of air being measured is from your lungs. As a result, the test is susceptible to falsely elevated measurements from any alcohol trapped in your mouth or esophagus. Alcohol may be retained in dental work, such as bridges or caps. Alcohol may remain in the esophagus after vomiting or due to any gastric reflux disorder. Mouthwash, breath mints, and other products may also contain alcohol and cause an erroneous BAC reading.

Alcohol isn't instantaneously absorbed into the blood. That means BAC results can sometimes be refuted with a "rising BAC" defense. A test that's delayed up to an hour after the initial stop may indicate intoxication. That's true even though the alcohol had not been sufficiently absorbed to cause impairment at the time of driving.

This argument works both ways, depending on the delay between the driver's last drink and the administration of the test. This is because an impaired driver can sober up while waiting to take the test. Regardless, there must be proof of intoxication while actually driving.

Defenses to Field Sobriety Tests

Law enforcement officers may administer a variety of field sobriety tests (FSTs) if they pull you over on suspicion of driving under the influence of alcohol or another substance. Police often record these tests on video. Field sobriety tests are usually administered after an officer decides to make the arrest. They help the state build a more solid case if you are charged. This supporting evidence may be used to counter claims that a breath test was inaccurate due to improperly calibrated equipment.

Field sobriety tests aim to highlight obvious physiological or mental impairment. They can be misleading, though, if you have other disabilities that interfere with passing the tests.

Police officers aren't medical professionals. They're not qualified to expertly judge specific physical cues. For example, the horizontal gaze nystagmus test — which requires you to follow a pencil, finger, or penlight visually — may be inadmissible in court. An officer can't reasonably determine nystagmus with their limited expertise. Yet this sort of evidence may lead to a conviction despite a passing BAC test result.

You may have the right to request an independent blood test. Blood tests provide the most reliable measurement of BAC. Results may be used to defend against Breathalyzer results that might otherwise lead to a DUI conviction.

Get Help From a DUI Lawyer if You're Charged with a DUI After Passing a Breathalyzer Test

Breathalyzer tests, field sobriety tests, and questions about being over the legal limit can feel overwhelming. Speak with a local DUI attorney to discuss your DUI charges and learn more about DUI laws. A defense attorney can be invaluable after a DUI arrest. A criminal defense attorney can offer legal advice and potentially help you avoid jail time or a lengthy driver's license revocation.