How Can You Challenge Breathalyzer Test Results in a DWI Case?
April 7, 2025
Breathalyzer tests are widely used to measure blood alcohol content (BAC). However, they’re not flawless. When deciding whether a breath test was administered correctly, knowing how to question the reliability of breathalyzer evidence can be a critical part of a criminal defense strategy.
James Hopkins Law Firm in Syracuse, New York, has over four decades of experience in providing criminal defense services for individuals facing a wide range of charges, including driving while intoxicated (DWI).
Below, Attorney James Hopkins provides an overview of breathalyzer tests, why they matter, and the ways you can challenge a breathalyzer test result if you've been accused of a DWI in New York.
Why Breathalyzer Evidence Matters
Breathalyzers are portable devices that estimate a driver’s BAC by analyzing a breath sample. Prosecutors frequently use these results to argue that a driver’s BAC surpassed legal limits. When the evidence appears airtight, defendants may feel pressured to accept a plea. However, breathalyzer devices can produce inaccuracies under certain conditions.
Therefore, it’s crucial to examine every aspect of how the breath test was administered and whether the device itself may have been compromised. Identifying these flaws can help a defendant show that the results aren’t conclusive proof of intoxication. A court might revoke driving privileges or impose penalties that linger on a person’s record for years.
Common Factors That Affect Breathalyzer Accuracy
A breathalyzer’s reading can change based on a variety of influences. Though law enforcement officers often place great weight on these numbers, certain aspects might lead to an inflated or unreliable result. Some common factors that can influence the accuracy of a breathalyzer test include:
Mouth alcohol residue: If a person used mouthwash or had a drink shortly before being tested, leftover alcohol in the mouth could skew the BAC reading.
Medical conditions: Individuals with acid reflux, diabetes, or other conditions might produce chemical compounds that trigger false positives or heightened readings.
Device maintenance: Improper calibration or infrequent servicing can affect a machine’s ability to generate accurate measurements.
Environmental issues: Fumes from chemicals or even certain types of paint can interfere with device sensors, causing them to register a higher reading.
Any one of these factors may cast potential doubt on a breathalyzer result. When a case transitions from the traffic stop to the criminal defense phase, pinpointing such elements can create a more persuasive argument in court.
Possible Procedural Errors by Law Enforcement
When a breath test is part of a DWI arrest, there are certain steps that an officer is supposed to follow. Failure to follow these steps can undermine the results. Some common errors might include:
A lack of observation period: Officers must generally observe a driver for a set time before administering a test to make sure no substances are consumed.
Rushed instructions: If an officer failed to explain how to blow into the device correctly, the sample might not reflect a driver’s true BAC.
Missing records: Maintenance logs for the breathalyzer should confirm that it was calibrated and functioning. If this documentation is incomplete, the result may be questionable.
Linking any of these points to actual mistakes during the traffic stop can help a defendant show that the test might not be reliable. This can be key if the breathalyzer result appears to be a key piece of evidence that the prosecution is using to prove intoxication.
The Basics of Observation Periods
Observation periods allow time for any residual alcohol in the mouth to dissipate, reducing the chance of a misleadingly high reading. Officers typically need to observe a driver for about 15 or 20 minutes, making sure that the driver doesn’t smoke, vomit, or ingest anything else that could confuse the test. If an officer shortcuts this process, the final reading might be compromised.
A well-prepared criminal defense often examines bodycam footage, dispatch logs, or any other timeline evidence to establish if the officer followed the correct waiting period. Challenging the observation period can strengthen a defense by demonstrating that there wasn’t enough time between the initial stop and the test.
For instance, if body camera footage shows the officer moving straight from the car stop to administering the test, that might indicate a violation of proper procedures. In that scenario, the defense could argue that the BAC reading might be inflated or entirely inaccurate.
Medical and Physiological Conditions
Some individuals have conditions that affect breathalyzer results. People with hypoglycemia or diabetes may produce substances in their breath that cause a reading indicating alcohol presence, even when they haven’t been drinking. Acid reflux or GERD can bring up alcohol from the stomach into the mouth, artificially boosting the tested amount of alcohol in the breath.
Respiratory issues: Conditions like asthma can lead to an inadequate breath sample, causing the machine to miscalculate.
Ketones: Diabetics can have elevated ketone levels, which devices sometimes interpret as alcohol.
If a defendant can show that these medical factors are present, the prosecution must address the possibility that the test wasn’t reflecting actual impairment. Rather than a certain guilty verdict, the case transforms into an analysis of whether the reading was compromised by existing health issues.
How to Challenge the Device’s Maintenance and Calibration
Breathalyzers require consistent calibration and routine checks to stay accurate. If the police department can’t provide records showing that the device was properly serviced, a criminal defense attorney might argue that the machine’s functionality was uncertain.
There are specific guidelines for how often these machines should be inspected and by whom. Asking for these maintenance logs is a standard part of a DWI defense strategy. If records show missed deadlines or incomplete servicing, the court might be more open to excluding or discounting the result.
How to Question the Test Administration Process
Breathalyzer results don’t exist in a vacuum. Instead, the administration process involves several key instructions and procedures. The key procedures include:
Instruction: The officer should explain what the driver needs to do, such as blowing steadily for a certain number of seconds.
Demo or practice attempts: Some devices prompt the officer to run a test sample or perform a zero-air check.
Multiple tests: The officer may perform two or more readings to confirm consistency in the results.
When a defendant reviews bodycam footage or cross-examines the officer, they might uncover issues like contradictory instructions or incomplete test attempts. Demonstrating that the officer didn’t follow the recommended process can lead the court to doubt the reliability of the result.
Additional Evidence That May Counter a Breathalyzer Result
Criminal defense strategies may also incorporate other forms of evidence that conflict with a breath test reading. Some common examples might include:
Field sobriety test performance: If the driver performed well on physical tasks, that might contradict a high BAC reading.
Witness testimony: Passengers or bystanders might claim that the driver showed no signs of impairment.
Restaurant or bar receipts: A record of how many drinks were purchased might show a lower intake than the breath test suggests.
Using this evidence can help create a broader narrative that the breathalyzer result wasn’t in line with the driver’s behavior and overall condition. This can, in turn, potentially lead a judge or jury to question whether the device was accurate or used correctly.
Breathalyzer Tests vs. Field Sobriety Tests
Law enforcement may administer standardized field sobriety tests, such as the walk-and-turn or one-leg stand, in addition to a breath test. These two pieces of evidence are frequently connected by prosecutors to show a pattern of intoxication. However, field sobriety tests can also be inaccurate due to poor road conditions, bad weather, or nerves.
If a defendant can show that they performed relatively well on field tests or that the tests weren’t conducted properly, the breathalyzer result may be viewed in a more skeptical light. The defense can argue that if the driver wasn’t swaying or stumbling, a high BAC reading might not reflect impairment.
Get in Touch Today
If you’re facing DWI charges and breathalyzer evidence is a concern, it's important to get in touch with an experienced criminal defense attorney who can help you thoroughly review your options.
James Hopkins Law Firm is skilled in helping its clients explore the potential ways to address questionable results. Attorney James Hopkins will discuss any available defenses with you and help you understand your best options for moving forward. Located in Syracuse, New York, the firm serves clients throughout Central and Northern New York, including Cicero, Baldwinsville, Rome, Utica, Rochester, Oswego, Watertown, and beyond. Reach out today to schedule a consultation.