When a driver blows into a breathalyzer and the result comes back above the legal limit, the first thought is often: it’s over. The machine doesn’t lie.
Here’s what the science actually says: breathalyzer machines can and do produce inaccurate results. They are instruments subject to calibration errors, operator mistakes, environmental interference, and physiological variation. Courts across Michigan have suppressed breathalyzer evidence for exactly these reasons.
For every drunk driving case at the Law Office of Grand Rapids OWI attorney Mark Caldwell, reviewing breathalyzer evidence is one of the first and most important steps. This article explains how breathalyzers work, where they fail, and what can be done when the results may not be accurate.
| A breathalyzer result is evidence – not a verdict. Michigan law gives defendants the right to challenge chemical test results, and experienced OWI attorneys do it successfully in courts across the state. |
Michigan’s Breathalyzer: The Intoxilyzer 9000
Michigan recently transitioned from the DataMaster DMT to the Intoxilyzer 9000 as its primary evidential breath test instrument. An arrest that occurred after this transition was almost certainly administered on the 9000.
The Intoxilyzer 9000 measures breath alcohol by detecting how infrared light is absorbed by ethanol molecules in the breath sample. It then calculates a BAC reading using a conversion ratio.
That conversion ratio is the first place where accuracy breaks down: the device assumes a specific relationship between breath alcohol and blood alcohol. But this ratio varies from person to person. The machine’s built-in assumption may not match an individual driver’s actual physiology.
| TRANSITION NOTE: Michigan was still deploying the Intoxilyzer 9000 alongside the older DataMaster DMT during a transition period. Arrests that fall within that transition window may have additional grounds to challenge which device was used and whether proper protocols were followed. |
7 Reasons a Breathalyzer Result Can Be Challenged in Michigan
- Improper Calibration
The Intoxilyzer 9000 must be calibrated on a regular schedule using reference solutions of known alcohol concentration. If the calibration was done incorrectly, or if the calibration records show an error, the resulting BAC readings are unreliable.
Defense counsel should request the full calibration log for the specific device used in the arrest. Gaps, anomalies, or deviations from required protocols are potential grounds for suppression.
- Failure to Observe the Required 15-Minute Waiting Period
Michigan police are required to observe a suspect for at least 15 minutes prior to administering a breathalyzer test. This waiting period ensures that any residual mouth alcohol – from belching, vomiting, or recent drinking – has dissipated. Mouth alcohol can cause a dramatically elevated false reading.
If the officer failed to properly document or conduct this 15-minute observation period, the test results may be challenged on that basis alone.
- Operator Error and Certification Failures
The officer administering the breathalyzer test must hold current certification to operate the specific device. If the certifying agency’s records show a lapse, an expired certification, or a procedural error in the administration, the result may be inadmissible.
The arresting officer’s training and certification records should be reviewed as a matter of course in every OWI case.
- Mouth Alcohol Contamination
Residual alcohol in the mouth – not alcohol absorbed into the bloodstream – can cause a breathalyzer to read significantly higher than actual blood alcohol. Sources include:
- Recent vomiting or burping
- Dental work, dentures, or oral piercings that trap liquid
- Mouthwash or breath spray containing alcohol
- Acid reflux or GERD, which can bring stomach content into the esophagus
GERD (gastroesophageal reflux disease) is one of the most significant physiological challenges to breathalyzer accuracy. Defendants with documented acid reflux should raise this factor with their attorney.
- Environmental and Ambient Interference
The Intoxilyzer 9000 is designed to detect ethanol but may also respond to other chemical compounds that share similar infrared absorption profiles. In industrial environments, or when a suspect has been exposed to certain solvents, paint fumes, or chemicals, false elevations are possible.
- Blood-Breath Partition Ratio Variation
The machine converts breath alcohol into estimated blood alcohol using a fixed partition ratio (typically 2100:1). But individual partition ratios vary naturally from roughly 1700:1 to 2400:1. When the defendant’s actual ratio sits at the low end of the spectrum, the device will systematically overestimate the BAC.
This is a technical defense but a legitimate one – particularly when a BAC reading falls close to a threshold such as .08% or .17%.
- Medical Conditions
Several medical conditions can affect breathalyzer results, including:
- Diabetes – ketoacidosis produces isopropanol, which some devices may detect as ethanol
- High-protein, low-carbohydrate diets (ketosis) – similar acetone production
- Fever – elevated body temperature can increase breath alcohol concentration
- Lung conditions – certain respiratory conditions may affect the accuracy of the breath-to-blood conversion
What About Blood Tests?
When a blood draw is given instead of a breath test, the challenges are different – but equally real. Blood test results in OWI cases can be challenged on the basis of:
- Chain of custody errors – who handled the sample and how
- Improper storage or contamination of the sample
- Lab analysis errors or procedural deviations
- Fermentation – improper preservation can cause alcohol to develop in the tube after collection
Blood test cases require a detailed analysis of the lab’s handling and testing procedures. These are not simple challenges, but they have succeeded in Michigan courts.
What Happens if the Breathalyzer Evidence Is Suppressed?
When a court grants a motion to suppress breathalyzer or blood test evidence, the prosecution’s case changes dramatically. In some cases, prosecutors may lack sufficient remaining evidence to proceed – resulting in dismissal of the OWI charge.
In other cases, the suppression of chemical test evidence leads to a negotiated reduction to a lesser charge – impaired driving or reckless driving – with significantly lower penalties and less impact on the record and license.
This is one of the most powerful tools in an OWI defense. It’s also one of the most technically demanding. Defendants need an attorney who understands the science, knows how to request and read calibration records, and knows when a motion to suppress is worth filing.
| For a complete overview of OWI defenses in Grand Rapids, see the companion article: Charged With an OWI in Grand Rapids? Here’s Exactly What Happens Next. |
Frequently Asked Questions
Can a driver refuse a breathalyzer test in Michigan?
A driver may refuse the post-arrest evidential breath test, but doing so triggers an automatic 1-year driver’s license suspension under Michigan’s implied consent law. Roadside preliminary breath tests and field sobriety tests are not required.
What is the Intoxilyzer 9000?
The Intoxilyzer 9000 is Michigan’s current official evidential breath test device, replacing the DataMaster (DMT). It uses infrared spectroscopy to measure ethanol in a breath sample. Like all breath test instruments, it is subject to calibration requirements and can produce inaccurate results under certain conditions.
How can a defendant find out if the breathalyzer was properly calibrated?
Defense counsel can obtain the calibration logs and maintenance records for the specific device used in an arrest through discovery. Attorney Mark Caldwell reviews these records in every OWI case handled by the firm.
Is a breathalyzer result enough to guarantee a conviction in Michigan?
Chemical test results are powerful evidence, but they are not automatically decisive. A skilled Grand Rapids OWI attorney can challenge the accuracy, administration, and admissibility of the test result. The prosecution still has the burden of proving guilt beyond a reasonable doubt.
An OWI Case Isn’t Over Because of a Number on a Machine.
A breathalyzer result is one piece of evidence. In nearly 20 years defending OWI cases in Kent County, Attorney Mark Caldwell has seen how often that evidence has weaknesses – weaknesses the prosecution is counting on defendants not to find.
A conviction is not inevitable. Call today for a free review of the actual evidence in the case.
✆ Call or text: (616) 915-6576
🌐 Free Consultation: markmcaldwell.com/contact
Related Articles
- Charged With an OWI in Grand Rapids? Here’s Exactly What Happens Next [Pillar]
- Michigan’s Super Drunk Law: What a BAC of .17+ Means for Your Case
- How Grand Rapids Sobriety Courts Work – And Why They Could Save Your Future
- What Happens to Your Driver’s License After an OWI in Michigan?
- OWI Expungement in Michigan – Clearing Your Record After a Drunk Driving Conviction
Attorney Mark Caldwell serves Grand Rapids, Kentwood, Wyoming, Walker, Grandville, Holland, Muskegon, Ionia and all of Kent, Ottawa, Muskegon, Ionia, Allegan, Mecosta, Newaygo, Osceola, Oceana, and Barry counties.
