Can a breathalyzer be wrong? While breathalyzer tests are the standard for measuring your blood alcohol content quickly and conveniently on the roadside and are often used as evidence against people accused of DWI, they aren’t actually the most accurate measure of intoxication. This is one of our favorite subjects here at Thiessen Law Firm, so let us explain. 

We’ve done a lot of writing about what to do when pulled over by the police and the inaccuracy inherent in all BAC tests for DWI, and always relish the opportunity to educate the public about common DWI misconceptions and how science affects the law. 

Whether you’re dealing with SCRAM bracelet false positives or an inflated reading on the breathalyzer test, if your future is resting in the hands of law enforcement’s ability to accurately measure toxicology, you might be in trouble. 

Call Mark Thiessen at Thiessen Law Firm today at (713) 864-9000 to protect yourself against overzealous prosecution and bad science. He’s argued successfully against hundreds of breath tests and may be able to do the same for you. 

Do breathalyzers give false positives?

Breath tests are wrong all the time. We can tell you this with some certainty, as we have taken countless DWI cases to court in which breath tests were incorrect, and won those cases for our clients based on the bad technology and incorrect procedures used to deploy it. 

Although the Intoxilyzer 9000 was evaluated extensively by the National Highway Traffic Safety Administration (NHTSA), its deployment onto the force was significantly delayed due to software issues and problems with false positives.

It’s no secret that the Intoxilyzer 9000 is often incorrect, with false positives popping up for several common conditions and tech issues, and we’re here to tell you that this reputation for inaccuracy is one of the most important reasons to take the breathalyzer test — but more on that later. 

How often are breathalyzers wrong?

This is the million-dollar question. How often are they wrong? Anecdotally, we can offer that we see them wrong pretty often. Scientifically, some studies suggest that all alcohol breathalyzer estimates are “subject to uncertainty.”

Determining just how often breathalyzers are incorrect is challenging due to factors like differences in device models, testing protocols, and environmental conditions, but what is certain is that the breathalyzer is not a perfect yardstick by which to measure intoxication.

The breathalyzer joins the standardized field sobriety test as the latest method for law enforcement to facilitate arresting you and charging you for a crime rather than accurately determining your level of intoxication. 

What is the margin of error on a breathalyzer test?

Or, in other words, how inaccurate is a breathalyzer test? All breathalyzer tests, including the Intoxilyzer 9000, are supposed to be rated within .01% of your actual blood alcohol content, an “acceptable margin of error” that we believe is already too high. 

But here’s the thing: breath tests are often nowhere near .01% of actual blood alcohol content, and studies have even shown that in large sample sizes, this is demonstrably not the case.

The difference between the mean breath and blood BAC results was .016% in the study above, which highlights the fact that every singleBAC result used to prosecute somebody for criminal activity should be subject to extreme and exhaustive scrutiny.

What may affect the result of a breathalyzer test?

What besides alcohol can set off a breathalyzer? Although breathalyzers are supposed to detect the amount of alcohol in your bloodstream, many things can affect the accuracy of its results. 

  1. Alcohol in the mouth, often resulting from mouthwash, breath spray, or recently consumed alcohol that has not been absorbed into the blood. 
  2. Medical conditions like acid reflux or diabetes can alter the contents of your breath and trigger false positives. 
  3. Medications, specifically asthma medications, NyQuil, and other over-the-counter medicines that contain alcohol, are notorious for messing with breathalyzer results. 
  4. Dietary factors can even influence the results. If you’re on a keto diet and your body is in ketosis it can cause your blood alcohol level to read as much higher than usual. 
  5. Environmental contaminants such as paint fumes, gasoline vapors, or cleaning supplies in a closed space (like a car) can mess with breathalyzer readings. 

Can I refuse a breathalyzer test?

Do you have to take a breathalyzer? While you technically can refuse a breathalyzer test, it might not always be the best idea to do so. Implied consent laws dictate that when you get behind the wheel of a vehicle on Texas roads, you also submit to requests from police officers who will ask you to take a chemical test to gauge your sobriety. 

You are legally allowed to refuse that breathalyzer test because it is not constitutional to force a driver to take a breath or blood test without a warrant, so why is refusing the breathalyzer often a bad idea for drivers?

We’ve said it once and we will say it again: Do not blow” is bad advice! Here’s why: 

  1. If you turn down the breathalyzer, a police officer can request a warrant and get your blood anyway. 
  2. Blood tests are typically more reliable than breath tests, and are much harder to fight in court. 
  3. Blood tests can also test for illegal drugs and medications that could have caused intoxication while taking the breathalyzer would only show that you were under the legal alcohol limit in Texas.
  4. The State of Texas might try to argue that common prescriptions like Adderall or Vyvanse are intoxicating on their own.

So if you’re asking yourself if you should refuse the breath test, remember that when faced with a choice between a blood test or a breathalyzer, the breathalyzer is generally the safer option. 

Found yourself on the wrong end of a false positive? Call Thiessen Law Firm today. 

So, can a breathalyzer test be wrong? YES, and they often are. The standard for measuring BAC for DWI cases was made the standard for convenience and cost, not because it is the best measure of actual intoxication. As is the case with standardized field sobriety tests, the police are less concerned with the truth about your intoxication than they are with the ability to easily make arrests and collect evidence that allows them to convict you. 

Mark Thiessen is an ACS-CHAL Forensic Lawyer-Scientistwho has mastered both the science and the law behind intoxication. He uses his unique background and expertise to fight for his clients accused of DWI who have fallen victim to junk science and overzealous prosecution and police work. 

If you or a loved one has been pulled over under suspicion of a DWI, whether you took the breath test or declined, call Thiessen Law Firm today at (713) 864-9000 or contact us online to get help. 

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Thiessen Law Firm

Mark Thiessen is an aggressive trial lawyer best known for his devotion to justice for his clients and high rank as a DWI Super Lawyer in Texas.