Challenging DUI Breath Test Results in Colorado: Machine Errors & Defenses

You took a breath test after your DUI arrest, and the prosecution is treating that BAC number as absolute proof of guilt. But breath test results are far from perfect. Colorado uses the Intoxilyzer 9000 for DUI cases, and despite law enforcement presenting these machines as infallible, they’re susceptible to calibration errors, operator mistakes, and physiological factors that can produce inaccurate results.

Understanding how to challenge breath test results may be the difference between conviction and dismissal. This guide covers the most effective defenses against breath test evidence in Colorado DUI cases.

If you were just arrested, start with: What to Do After a DUI Arrest in Colorado: Your First 24-48 Hours

The Problem with Breath Testing Science

The Intoxilyzer 9000 doesn’t directly measure your blood alcohol concentration. It measures alcohol in your breath, then multiplies that number by a 2100:1 partition ratio to estimate your BAC. The problem? That ratio assumes everyone’s blood-to-breath alcohol ratio is identical.

Scientific research shows partition ratios actually range from 1300:1 to 3000:1 or higher. If your partition ratio is 1500:1, the machine will overestimate your BAC by roughly 40%. Someone with a true BAC of 0.057% could register as 0.08%, which means the difference between legal and illegal.

Top Breath Test Defenses in Colorado

Calibration and Maintenance Errors

Colorado law (5 CCR 1005-2) requires strict calibration and maintenance of breath testing devices. The Intoxilyzer 9000 must be certified by the Colorado Department of Public Health and Environment (CDPHE). Your attorney can subpoena:

•       Device certification records
•       Calibration logs and control test results
•       Maintenance records
•       Simulator solution expiration dates

If the device wasn’t properly certified, used expired calibration solution, or failed control tests, your results may be inadmissible.

Mouth Alcohol Contamination

Breath tests measure deep lung air, but any alcohol in your mouth drastically inflates readings. Colorado requires a 20-minute observation period before testing to prevent mouth alcohol contamination. Common sources include:

•       GERD, acid reflux, or hiatal hernia (stomach alcohol rises into your throat)
•       Burping or belching during observation period
•       Recent drinking (within 15-20 minutes)
•       Dental work, dentures, or dental appliances
•       Mouthwash or breath spray

If you have GERD or burped during the observation period, medical records and body camera footage can support this defense.

Operator Error

Officers must be certified as Evidential Breath Alcohol Testing (EBAT) operators and follow strict protocols. Common errors:

•       Inadequate observation period (officer distracted or left the room)
•       Expired operator certification (must recertify every 180 days)
•       Insufficient breath sample
•       Failure to monitor for regurgitation

Your attorney can review body camera footage, dashcam video, and certification records to identify violations.

Ketosis and Medical Conditions

The Intoxilyzer 9000 detects substances that absorb infrared light like ethanol, including acetone from ketosis. Your body produces ketones when burning fat for energy, which occurs with:

•       Diabetes (Type 1 or Type 2)
•       Low-carb diets (keto, Atkins, paleo)
•       Fasting or skipping meals

Medical records and expert testimony can establish that ketones interfered with your test results.

Rising Blood Alcohol

Alcohol takes 15 minutes to 3 hours to absorb into your bloodstream. Your BAC may have been legal while driving but rose to an illegal level by the time you took the breath test at the station.

For example, if you had your last drink 15 minutes before driving, your BAC might have been 0.05% (legal) while driving but climbed to 0.09% (illegal) 45 minutes later at the station. A forensic toxicologist can calculate your likely BAC at the time of driving.

This defense works best when there was significant delay between the stop and breath test, and your BAC was close to the legal limit.

The 7-Day DMV Hearing Deadline

You have only 7 days from your arrest to request a DMV Express Consent hearing. This hearing is separate from your criminal case and gives you a chance to challenge the breath test results to protect your driver’s license.

At the DMV hearing, your attorney can challenge whether the officer had reasonable grounds for arrest, whether the test was properly administered, whether the device was certified, and whether your BAC was actually above the legal limit.

For detailed instructions: How to Request a Colorado DMV Hearing After DUI Arrest

When Breath Test Results Can Be Suppressed

Your attorney can file a motion to suppress breath test evidence entirely if:

•       The stop or arrest was illegal (no reasonable suspicion or probable cause)
•       You weren’t properly advised of Express Consent
•       The device wasn’t certified by CDPHE
•       The operator’s certification had expired
•       Mandatory testing procedures under 5 CCR 1005-2 weren’t followed

Successful suppression can severely weaken the prosecution’s case, often leading to dismissed or reduced charges.

What About Breath Test Refusal?

If you refused the breath test, you face automatic license revocation (typically one year for a first refusal) under Colorado’s Express Consent law. While refusal eliminates BAC evidence against you, it can be used as evidence of consciousness of guilt, and officers can still obtain a warrant for forced blood draw.

Learn more: What Happens If You Refuse a Breathalyzer in Colorado?

Why You Need an Experienced DUI Attorney

Breath test defenses require technical knowledge of both law and science. An experienced attorney will immediately request your DMV hearing, obtain comprehensive discovery (calibration records, maintenance logs, officer certifications), review body camera footage for violations, retain expert witnesses, file suppression motions when appropriate, and negotiate from a position of strength.

The difference between a DUI conviction and dismissal often comes down to how effectively your attorney challenges the breath test evidence.

Get Help Challenging Your Breath Test Results

At Right Law Group, we’ve successfully challenged breath test results in hundreds of Colorado DUI cases. Our team includes former prosecutors who know how the state builds its case and how to dismantle breath test evidence through aggressive discovery and expert testimony.

Why choose us:

•       Former prosecutors who know prosecution strategies
•       Available 24/7 to file your DMV hearing immediately
•       Deep understanding of breath testing science
•       Proven track record suppressing breath test evidence
•       Offices in Colorado Springs, Castle Rock, Denver, and Highlands Ranch

Contact Right Law Group today for your free consultation. Call (719) 822-6227 or reach out 24/7. When your freedom is at stake, the Right Defense Matters.

Related Articles:

•       What to Do After a DUI Arrest in Colorado: Your First 24-48 Hours
•       How to Request a Colorado DMV Hearing After DUI Arrest
•       What Happens If You Refuse a Breathalyzer in Colorado?
•       First DUI Offense in Colorado
•       Second DUI in Colorado: Enhanced Penalties & Defense Strategies
•       Colorado DUI Penalties: Complete Guide

Disclaimer:

This article is provided for informational purposes only and does not constitute legal advice. The information contained herein is accurate to the best of our knowledge as of December 2025 but may not reflect the most current legal developments. Each case is unique, and outcomes depend on specific facts and circumstances. Laws and court procedures may vary by county and jurisdiction within Colorado. If you are facing criminal charges, consult with a qualified Colorado criminal defense attorney to discuss your specific situation.

Colorado Bar Advertising Disclaimer: The choice of a lawyer is an important decision and should not be based solely upon advertisements. Past results do not guarantee future outcomes. No attorney-client relationship is created by reading this article or contacting our firm for a consultation.