You may be wondering if a faulty breathalyzer can save you from a DUI conviction in Michigan.
Michigan DUI charges can sometimes be dismissed if the breathalyzer was not properly calibrated. Courts require strict compliance with maintenance, certification, and accuracy standards. If records show errors, defense lawyers can file suppression motions that weaken or collapse the prosecution’s case.
This article explains calibration rules, common failures, case law, and how attorneys use these issues to challenge DUI prosecutions.
Michigan Breathalyzer Calibration Requirements
Michigan law requires that DataMaster DMT breath-testing instruments undergo periodic calibration checks and accuracy verifications. The Michigan State Police (MSP) Breath Alcohol Unit maintains detailed records on simulator solutions, calibration logs, and instrument certifications. These rules are designed to ensure reliability in DUI prosecutions, where blood alcohol concentration (BAC) results often determine guilt or innocence.
Improper calibration undermines reliability. Courts recognize that breath test evidence is only admissible if the instrument meets statutory and administrative requirements. Defense lawyers frequently request calibration logs during discovery to verify compliance.
Table: Calibration Problems and Legal Consequences
| Calibration Problem | Legal Consequence | Defense Strategy |
|---|---|---|
| Missed required calibration checks | Test results may be suppressed | File motion to exclude BAC evidence |
| Incorrect simulator solution used | Unreliable results | Cross-examine state witnesses; highlight deviations |
| Poor record-keeping or missing logs | State cannot prove reliability | Argue due process violation; request dismissal |
| Operator not certified | Improper administration of test | Challenge admissibility under evidentiary rules |
| Instrument out of service/not recertified | Results excluded from trial | Seek full dismissal or favorable plea reduction |
How Defense Lawyers Use Calibration Errors
Defense attorneys file motions to suppress breath test results when calibration records reveal problems. If BAC evidence is excluded, the prosecution may lack sufficient proof beyond a reasonable doubt. In many cases, this forces charge reductions to lesser offenses such as “Operating While Visibly Impaired” (OWVI) or even dismissals when no other evidence of impairment exists.
Cross-examination of state witnesses focuses on maintenance logs, solution batch numbers, and the qualifications of the operator. Experts may testify that a calibration failure undermines scientific reliability. Without credible BAC results, prosecutors may be unable to prove statutory limits of 0.08% (or 0.02% for underage drivers).
Case Law Examples in Michigan
Michigan appellate courts have repeatedly considered breath-test reliability. For example, courts have suppressed results when calibration documentation was incomplete or when operators lacked proper certification. While rulings vary depending on the facts, the underlying principle is clear: reliability is a prerequisite for admissibility. Defense lawyers must scrutinize every log and certification.
When Charges May Be Dropped
- No alternative evidence: If the state relies solely on breath results and they are excluded, dismissal is more likely.
- Weak corroboration: Without strong officer observations or field sobriety results, prosecutors may concede dismissal or reduction.
- Pattern of error: If calibration problems affect multiple cases at a police department, systemic challenges may succeed.
Other Evidence Still Matters
Even if breath results are excluded, prosecutors may still rely on officer testimony, dash-cam or body-cam video, field sobriety test performance, or blood test evidence. That means dismissal is not automatic. The best defense strategy blends calibration challenges with broader constitutional and evidentiary arguments.
Practical Defense Strategies
- Request calibration and maintenance logs immediately in discovery.
- Hire an expert witness to analyze simulator solution records and calibration procedures.
- File pretrial motions to suppress faulty results.
- Challenge chain of custody for simulator solutions and device logs.
- Prepare cross-examination of breath-test operators and state police technicians.
Frequently Asked Questions
Does a bad calibration always mean dismissal?
No. It can lead to suppression of results, but prosecutors may proceed with other evidence.
How often must breathalyzers be calibrated in Michigan?
They must be checked and certified on a regular schedule by MSP technicians, with logs kept for each unit.
What if the operator was not certified?
That can be grounds to exclude the test, since only certified operators may administer DataMaster tests in Michigan.
Can I request calibration logs for my case?
Yes. Defense counsel should subpoena or request logs during discovery.
Will prosecutors drop the case if results are excluded?
It depends. If other strong evidence exists, they may still pursue conviction.
Can I win my DUI if the breathalyzer wasn’t calibrated?
You may. Suppression of unreliable results often forces reductions or dismissals, but success depends on the full evidence picture.
Is calibration the same as maintenance?
No. Calibration involves accuracy verification; maintenance includes overall functionality checks and repairs.
Call for a Free Consultation
If you believe a faulty breathalyzer threatens your future, call 269-808-8007 for a free consultation. Our Michigan DUI defense team reviews calibration records in every case and knows how to challenge unreliable BAC evidence.
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