How Can You Challenge Breathalyzer Results in a DUI Case?
Like any machine, breathalyzers are subject to human error, mechanical issues, and procedural flaws. The law recognizes these weaknesses, which is why defendants in DUI cases have the right to contest and challenge the validity of the state’s evidence.
I'm Attorney Carl Jensen Jr., and my clients often ask 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. As someone who has dedicated his practice to DUI defense in Great Falls, Montana, and surrounding areas, I know that questioning breathalyzer results can make all the difference in protecting a client’s record, freedom, and reputation.
A DUI charge can impact every part of your life, from your career to your personal relationships. That’s why I take the time to carefully examine every aspect of how the state collected and presented its evidence.
Let me explain how breathalyzer results can be challenged, what Montana law says about their use, and why a strong criminal defense strategy must constantly scrutinize this type of evidence.
Breathalyzers Under Montana Law
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.
Breathalyzers measure alcohol in a person’s breath and then apply a mathematical formula to estimate 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. My job as a defense attorney is to test that assumption.
Grounds for Challenging Breathalyzer Results
There are several reasons breathalyzer results may not hold up in court. As part of every criminal defense case I handle, I 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 he examines closely.
Operator Error
Even a perfectly functioning machine can produce unreliable results if the officer administers the test incorrectly. 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 measure blood alcohol directly—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, it's an attorney's job to 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 defending a client, I focus on gathering evidence that can weaken the prosecution’s case. Some of the most valuable information includes:
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 enables me to construct a robust criminal 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 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.
A criminal defense attorney uses this type of evidence to show the court that the breathalyzer is not a perfect measure of intoxication. Science can be a powerful tool for balancing the scales in favor of the defense.
Constitutional Protections
Challenging breathalyzer results is not only about science—it’s also about protecting constitutional rights. Under both Montana law and the U.S. Constitution, defendants have the right to confront the evidence used against them. That means the defense has the right to question the reliability of the breathalyzer, the officer's competence, and the fairness of the procedures used.
If breathalyzer evidence is admitted without proper scrutiny, it could violate a defendant’s right to a fair trial. A criminal defense attorney must make sure every safeguard is upheld and that no unreliable evidence is allowed to influence the outcome unfairly.
Practical Implications for Clients
When breathalyzer results are successfully challenged, the entire case can shift. Without a reliable BAC reading, prosecutors often have to fall back on less persuasive evidence, such as officer observations. That evidence is far more subjective and easier to challenge in court.
This can result in reduced charges, lighter penalties, or, in some cases, complete dismissal. In the practice of criminal defense, challenging breathalyzer results is often the difference between conviction and acquittal.
Building a Strong Defense Strategy
I approach every DUI case with the understanding that the state’s evidence must be tested at every point. I review the stop, the arrest, the administration of the test, and the results themselves. No detail is too small; even minor errors can undermine the accuracy of a breathalyzer test.
My goal is not only to defend my clients against the charges but also to protect their future. A DUI conviction can affect employment, housing, and personal relationships for years to come. Criminal defense is about more than fighting charges—it’s about safeguarding your life.
When to Seek Legal Help
Time is critical in DUI cases. The sooner you reach out for representation, the more opportunities we 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. My responsibility is to match that effort with a thorough and determined defense. You deserve an attorney who will thoroughly examine every piece of evidence and vigorously advocate for your rights.
Reach Out Today
Breathalyzer results may appear convincing, but they aren’t beyond question. In Montana DUI cases, these machines can be prone to error, misused by officers, and influenced by outside factors.
I approach every case with the understanding that the state must prove guilt beyond a reasonable doubt, and breathalyzer evidence often leaves room for doubt. By focusing on calibration records, officer training, medical conditions, and constitutional safeguards, I strive to build a criminal defense strategy that challenges the prosecution’s evidence at every level. My clients 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. Strategic criminal defense can effectively challenge those results, safeguarding not only the outcome of your case but also your future. At the law firm of Attorney Carl Jensen Jr., I proudly serve the residents of Great Falls, Montana, and the surrounding communities. Call today to schedule a consultation.