How Can You Challenge Breathalyzer Results in a DUI Case?
A DUI charge can impact every part of a person’s life, from their career opportunities to their personal relationships. However, breathalyzers, like any machine, are subject to human error, mechanical issues, and procedural flaws. The law recognizes these weaknesses, which is why defendants have the right to contest and challenge the validity of the state’s evidence.
At Carl Jensen Jr., I am often asked whether breathalyzer results are absolute proof of guilt in a DUI case. Under Montana law, the results of a breath test carry significant weight, but that does not mean they’re beyond question. Questioning breathalyzer results can make all the difference in protecting a client’s record, freedom, and reputation.
Here, I will explain how breathalyzer results can be challenged, what Montana law says about their use, and why a strong criminal defense strategy must scrutinize this type of evidence.
Montana Law Governing Breathalyzers
Montana law allows law enforcement officers to request a breath test when they suspect a driver is under the influence of alcohol. Refusing a test can result in automatic license suspension and other penalties. However, agreeing to a test does not mean the results are immune from legal scrutiny or challenge.
Breathalyzers measure the alcohol in a person’s breath and then apply a mathematical formula to estimate the driver's blood alcohol concentration (BAC). While the law treats these results as strong evidence, they aren’t infallible.
Criminal defense strategies often focus on uncovering whether the device was properly maintained, whether the officer followed the required procedures, and whether outside factors may have distorted the results. The foundation of a DUI prosecution may rest on the assumption that the breathalyzer was accurate; however, by working with an experienced criminal defense attorney, you have the legal right to challenge that assumption in court.
Grounds for Challenging Breathalyzer Results
There are several reasons why breathalyzer results may not hold up in court. As part of every criminal defense case, I work with my clients to evaluate the evidence to determine whether any of these factors played a role.
Machine calibration and maintenance: Montana law requires breathalyzers to be routinely calibrated and tested to verify accuracy. If a machine were overdue for maintenance or had a history of problems, the results can be called into question. Records of calibration are critical pieces of evidence that I examine closely.
Operator error: Even a perfectly functioning machine can produce unreliable results if the officer does not administer the test correctly. Law enforcement officers must be properly trained and follow a strict process when conducting tests. Any deviation from this procedure could create doubt about the reliability of the results.
Medical conditions and physiological factors: Certain health conditions, such as acid reflux, diabetes, or asthma, can affect the accuracy of breathalyzer readings. For example, individuals with gastroesophageal reflux disease may have alcohol from the stomach rise into the mouth, artificially inflating the BAC reading. A thorough criminal defense strategy considers whether medical conditions may have influenced the test results.
Environmental and external factors: Chemicals in the environment, such as paint fumes, cleaning products, or even exposure to gasoline, can sometimes interfere with the machine’s sensors. Additionally, residual alcohol in the mouth from cough syrups, mouthwash, or recent dental work may skew the results.
Timing of the test: Alcohol levels in the body fluctuate depending on when the last drink was consumed. If the test was administered long after the person was stopped, the results may not accurately reflect their BAC while driving. This creates an opportunity for the defense to argue that the results are misleading.
Why Breathalyzers Are Not Foolproof
Breathalyzers are often presented as scientific and precise, but in truth, they’re estimations based on assumptions. The device does not directly measure blood alcohol; instead, it measures breath alcohol and uses a formula that may not apply equally to every individual.
For instance, body temperature, breathing patterns, and even physiological differences can affect how alcohol is processed. Two people drinking the same amount of alcohol may show very different results on a breathalyzer test. In criminal defense cases, your attorney can demonstrate these potential inaccuracies and explain to the court why the state’s evidence may not be as reliable as it appears.
Key Evidence to Review in DUI Cases
When facing a DUI charge, it's essential to work with your attorney to gather evidence that can weaken the prosecution's case. Some of the most valuable information you should collect includes the following.
Maintenance and calibration records for the breathalyzer device
The officer’s training certifications and procedural notes
Video recordings from the traffic stop or arrest
Witness statements describing the client’s behavior and speech
Medical documentation that could explain unusual readings
This evidence allows your attorney to build a strong defense that highlights the weaknesses in the state’s case and raises reasonable doubt about the accuracy of the test results.
Scientific Challenges in Court
Scientific testimony also often plays a central role in DUI trials. Expert witnesses can explain the science behind breathalyzers and highlight their limitations. For example, they may discuss how high body temperatures can artificially inflate BAC readings or how mouth alcohol can contaminate results.
As a criminal defense attorney, I can utilize expert witness testimony to demonstrate to the court that the breathalyzer is not an infallible measure of intoxication. Science can be a powerful tool for balancing the scales in favor of the defense.
How an Attorney Can Help
At Carl Jensen Jr., I approach every DUI case with the understanding that the state’s evidence should be tested at every point. I will work alongside you to review the traffic stop, the administration of the test, the arrest, and the results themselves. No detail is too small, because even minor errors can undermine the accuracy of a breathalyzer test.
My goal is not only to defend you against the charges but also to protect your long-term future. A DUI conviction can often affect employment, housing, and personal relationships for years. Criminal defense is about more than fighting charges—it’s about safeguarding a client’s life. Therefore, the sooner you reach out for representation, the more opportunities you have to challenge the evidence and build a strong defense.
Breathalyzer results may seem intimidating at first, but with the right approach, they can be effectively challenged. As an experienced criminal defense lawyer in Montana, I have seen how aggressively prosecutors pursue DUI cases. I strive to match that effort with a thorough and determined defense.
Reach Out To a Skilled Criminal Defense Attorney Today
Breathalyzer results may appear convincing, but they aren’t infallible. In DUI cases, these machines can be prone to error, misused by officers, and influenced by outside factors. By focusing on calibration records, officer training, medical conditions, and constitutional safeguards, you and your attorney can build a criminal defense strategy that challenges the prosecution’s evidence at every level.
At Carl Jensen Jr., I approach every case with the understanding that the state must prove guilt beyond a reasonable doubt. You deserve the strongest defense possible, and that begins with holding the state accountable for the reliability of its breathalyzer results.
No DUI case is hopeless, and no breathalyzer is flawless. With the right criminal defense, those results can be successfully challenged to help protect the outcome of your case. Located in Great Falls, Montana, I serve clients throughout the surrounding communities. Contact me firm today to schedule a consultation.
