Challenging Breath Tests in Colorado DUI Cases - Colorado DUI Attorney

Challenging Breath Tests in DUI Cases

Challenging the Reliability of Breath Test Evidence in DUI Cases

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Challenging Breath Test Results in Colorado DUI Cases

Breath test evidence is often one of the most important parts of a Colorado DUI prosecution. In many cases, prosecutors rely heavily on breath alcohol results obtained through Colorado’s Intoxilyzer 9000 breath testing machine.

However, breath test results are not automatically accurate, conclusive, or immune from challenge. Our DUI Defenses in Colorado resource discusses how chemical testing issues, constitutional violations, and evidentiary challenges may affect DUI prosecutions.

At The Lawrence Law Firm, we carefully evaluate the reliability of breath testing evidence in every DUI case. While chemical testing can be powerful evidence, it is only one part of the prosecution’s case and must still be viewed alongside the surrounding facts, officer observations, and constitutional issues.

Colorado Uses the Intoxilyzer 9000

Colorado law enforcement agencies currently use the Intoxilyzer 9000 for evidentiary breath testing in DUI cases.

The machine is designed to estimate blood alcohol concentration (“BAC”) by measuring alcohol content in a person’s breath sample.

Breath testing commonly occurs:

  • at a police station,
  • detention facility,
  • or DUI processing center,
    after arrest.

In many cases, the prosecution uses breath results to pursue:

  • DUI per se charges,
  • aggravated sentencing allegations,
  • or enhanced penalties for high BAC results.

However, despite the scientific appearance of breath testing, these cases often involve significant procedural and technical issues.

Breath Test Results Are Not the Entire DUI Case

One important reality in DUI litigation is that breath test evidence is not the entirety of the state’s case.

In law school and trial advocacy training, a common question often asked is:

“How would you prove the DUI charge beyond a reasonable doubt without the chemical test?”

That question matters because prosecutors frequently rely on much more than just the BAC number itself.

Even in cases involving disputed breath testing, prosecutors may still point to:

  • admissions regarding alcohol consumption,
  • driving behavior,
  • field sobriety test performance,
  • officer observations,
  • slurred speech,
  • odor of alcohol,
  • balance issues,
  • and body-worn camera footage.

In practice, juries often evaluate the entire interaction shown on video—not just the breath result alone.

Because of this, challenging a breath test does not automatically mean the case disappears. Instead, it may weaken the prosecution’s evidence, create reasonable doubt, reduce sentencing exposure, or improve negotiating leverage.

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The 20-Minute Deprivation Period

Colorado breath testing procedures generally require a 20-minute deprivation or observation period before administration of the breath test.

During this period, the subject should generally not:

  • eat,
  • drink,
  • smoke,
  • vomit,
  • regurgitate,
  • or place objects into their mouth.

The purpose of the deprivation period is to reduce the risk of residual mouth alcohol affecting the breath result.

Residual alcohol in the mouth can artificially elevate test readings and potentially create inaccurate results.

In some cases, important legal and factual issues may arise regarding:

  • whether the observation period was properly completed,
  • whether the officer continuously observed the subject,
  • whether interruptions occurred,
  • or whether bodycam footage contradicts official reports.

These issues may become important during motions practice or trial.

Common Defenses to Breath Test Results

Improper Observation Procedures

Failure to properly conduct the 20-minute deprivation period may affect reliability.

Potential issues include:

  • breaks in observation,
  • distractions,
  • incomplete observation,
  • or undocumented interruptions.

Video evidence can sometimes become extremely important in these cases.  Learn more about rising BAC defense.

Mouth Alcohol Contamination

Breath tests are intended to measure deep lung air, not residual alcohol remaining in the mouth.

Potential causes of mouth alcohol include:

  • belching,
  • acid reflux,
  • GERD,
  • vomiting,
  • chewing tobacco,
  • dental appliances,
  • or recent alcohol consumption.

Residual mouth alcohol may potentially produce falsely elevated readings.

Rising Blood Alcohol Issues

Alcohol absorption takes time. A person’s BAC may continue rising after driving has already occurred.

This issue commonly arises where:

  • drinking occurred shortly before driving,
  • testing was delayed,
  • or the defendant appeared less impaired than the reported BAC.

The relevant legal issue is generally the BAC at the time of driving—not simply the BAC at the time of testing.

Machine Maintenance and Calibration

Like any scientific instrument, breath testing devices require maintenance, calibration, and compliance with established procedures.

Potential issues may include:

  • maintenance irregularities,
  • operator error,
  • calibration problems,
  • software issues,
  • or inadequate recordkeeping.

Defense attorneys often review maintenance records and certification materials as part of case preparation.

Medical Conditions Affecting Results

Certain medical conditions may affect breath testing accuracy, including:

  • GERD,
  • acid reflux,
  • diabetes,
  • certain diets,
  • and other physiological conditions.

These issues can sometimes complicate interpretation of breath alcohol evidence.

DUI vs. DWAI: Why Breath Challenges Still Matter

One important issue in Colorado DUI cases is that challenging the breath test does not necessarily eliminate all criminal exposure.

Even if a jury rejects a DUI charge, jurors may still consider the lesser included offense of DWAI (Driving While Ability Impaired).

Under Colorado law:

The phrase “slightest degree” is extremely broad and can create significant challenges for defendants at trial.

Prosecutors may argue that:

  • even if the BAC result is questionable,
  • the officer observations,
  • admissions,
  • driving conduct,
  • or bodycam footage
    still demonstrate some level of impairment.

As a result, DUI trials are often not simply about whether a person was intoxicated—but whether the prosecution can prove impairment beyond a reasonable doubt under the applicable legal standard.

Why Challenging Elevated BAC Results Can Still Be Critical

Even where the prosecution still pursues a DWAI theory, breath test challenges can remain extremely important.

This is particularly true in cases involving elevated BAC results.

In Colorado, higher BAC readings may trigger:

  • aggravated sentencing considerations,
  • mandatory jail exposure,
  • enhanced probation requirements,
  • alcohol treatment conditions,
  • and other sentencing consequences.

For example, BAC allegations of .15 or higher may significantly affect sentencing outcomes and negotiations.

Because of this, reducing the reliability or weight of the breath result can still substantially impact the overall case—even where prosecutors continue pursuing impairment-based charges.

Body-Worn Camera Evidence Often Becomes Central

In many DUI trials, body-worn camera footage becomes one of the most important forms of evidence.

Jurors often evaluate:

  • speech patterns,
  • balance,
  • coordination,
  • demeanor,
  • responsiveness,
  • and overall appearance.

This is one reason why breath testing litigation is rarely isolated from the rest of the evidence in the case.

A jury may hear:

  • a disputed breath result,
  • officer testimony,
  • and simultaneously watch bodycam footage for themselves.

As a result, effective DUI defense often requires analyzing the entire investigation—not just the machine result alone.

Breath Test Cases Frequently Involve Technical Litigation

Litigating breath test reliability may involve review of:

  • Intoxilyzer maintenance records,
  • deprivation period compliance,
  • operator certifications,
  • bodycam footage,
  • testing procedures,
  • calibration documentation,
  • and scientific evidence.

These issues may arise during:

  • suppression hearings,
  • evidentiary motions,
  • negotiations,
  • or trial.

Speak With a Colorado DUI Defense Attorney

If you were arrested for DUI in Colorado, it is important to understand that breath test evidence is only one part of the case. The legality of the stop, the officer’s observations, video evidence, and testing procedures may all affect the outcome.

At The Lawrence Law Firm, we represent clients charged with DUI, DWAI, felony DUI, and related offenses throughout the Denver metro area.

To discuss your case with an experienced Colorado DUI defense attorney, contact our office for a free consultation.

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