Challenging the Breath Test in a Phoenix DUI
Arizona’s evidentiary breath machine, the Intoxilyzer 8000, is treated like a lie detector for your blood alcohol. It is not. It must be calibrated, maintained, and operated exactly right, and when it is not, the reading can be thrown out.
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Can a breathalyzer result be thrown out in Arizona?
Quick answer: Yes. A breath result is only admissible if the State proves the machine was properly calibrated and maintained and that the test was administered correctly, including a 15-minute observation. Mouth alcohol, radio-frequency interference, maintenance failures, and operator error all inflate readings, and any of them can get the result suppressed or discredited.
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Former Prosecutors · Law Enforcement · Public Defenders
When you call Tamou Law Group, you reach a firm that handles criminal defense exclusively, with serious experience defending DUI cases across Arizona. Our team includes former prosecutors and law enforcement officers, so we know exactly how the State builds these cases, and where they fall apart.
At many large firms, the name on the building is a marketing figurehead, you rarely get them on the phone and your case goes to a junior associate. When you hire Tamou Law Group, your case is handled by a full team of attorneys, not associates, including Michael Tamou.
The Machine Is Not Infallible
A breath test estimates blood alcohol indirectly, and every step can go wrong.
The Intoxilyzer does not measure your blood, it measures alcohol in a breath sample and estimates your blood level using assumptions that vary from person to person. On top of that estimate sit the machine’s condition, the testing environment, and the officer’s technique.
Arizona law and Rule 702 require the State to establish that the result is reliable before a jury ever hears it. That opens the door to challenge calibration, maintenance, the observation period, and the operator, any weak link makes the number suspect.
The 15-Minute Observation & Mouth Alcohol
Alcohol lingering in your mouth can spike a reading far above your true level.
Residual mouth alcohol, from a burp, acid reflux, dental work, breath spray, or recent drinking, can send a breath reading far above your actual blood level. To rule it out, Arizona requires the officer to continuously observe you for 15 minutes before the test, with no burping, belching, vomiting, or regurgitation.
In reality this observation is often not done properly, the officer looks away, does paperwork, or the “15 minutes” is really eight. When the observation fails, the reading is unreliable, and it is a documented, provable defect we raise directly.
Certain medical conditions make mouth alcohol worse; see our medical defenses guide (GERD, diabetes, diet).
Calibration, Maintenance & Interference
The machine has to be certified, serviced, and free of interference. Records tell the story.
We obtain the machine’s full history and attack:
- Calibration & accuracy checks, whether they were current, in tolerance, and properly documented.
- Maintenance and repair logs, a machine flagged for errors or repaired around your test date is suspect.
- Radio-frequency interference (RFI), police radios and devices can corrupt a reading.
- Partition ratio & temperature, the assumed blood-to-breath ratio does not fit everyone and skews high for many.
- Operator certification & procedure, an uncertified or careless operator invalidates the test.
The paper trail is decisive, and the State does not volunteer it. See records & discovery for how we force its production.
What the State Must Prove for a Valid Breath Test
A breath result is admissible only if every one of these boxes is checked. We audit all of them.
Required for a Valid Result
- Continuous 15-minute observation, documented, no burp/belch/vomit.
- Current calibration & quality-assurance (QAS) records in tolerance.
- Two breath samples that agree within the required tolerance.
- A certified operator following the approved procedure.
- No radio-frequency interference (RFI) from police radios or devices.
What Falsely Raises a Breath Reading
- Mouth alcohol from burping, reflux, dental work, or breath spray.
- A partition ratio that runs high for you (the machine assumes 2100:1).
- Temperature, breathing pattern, and residual-alcohol timing.
- A machine recently flagged or repaired around your test date.
Suppress the Breath, Shrink the Case
Knock out or discredit the breath result and the prosecution often folds.
If the breath result is suppressed or seriously undermined, an (A)(2) “per se” charge can collapse and an impairment charge gets much weaker. That is why the breath machine is one of the first things we attack.
Part of a full defense, see our Top 10 DUI defenses and Phoenix DUI defense. Call 623-321-4699, 24/7.
The Experts We Bring to DUI Cases
A DUI is a science case. We bring the specialists who take the State’s numbers apart, click any to see how.
Forensic Toxicologists
BAC & Absorption
Independently review the blood and breath results, the absorption curve, and whether the alleged number reflects your true level at the time of driving.
Breath-Test Analysts
Intoxilyzer & Calibration
Examine the machine’s calibration and maintenance logs and the 15-minute observation, exposing mouth alcohol, radio interference, and operator error that inflate readings.
Blood & Lab Experts
Gas Chromatography
Audit the blood draw, storage, fermentation risk, lab protocol, and reported uncertainty, where applying the margin of error can drop the reading below the threshold.
Medical Experts
GERD, Diabetes & Diet
Explain how acid reflux, diabetes, and low-carb diets can push a breath reading upward, independent of how much alcohol was actually consumed.
Field Sobriety Experts
NHTSA Protocol
Evaluate whether the standardized field sobriety tests were administered and scored correctly, and whether the “clues” really show impairment.
Records & Discovery Specialists
Maintenance & Logs
Pull the full calibration history, repair records, and the discovery the State would rather not produce, the paper trail that often reveals an unreliable machine.
Awards & Recognition
Our recognition for Phoenix DUI defense is independently verified, click any award to confirm it:
- National Trial Lawyers Top 100
- National Trial Lawyers Top 40 Under 40
- Elite Lawyer 2026 – Criminal Defense
- Super Lawyers – Southwest
- National College for DUI Defense (NCDD)
Together, these place Tamou Law Group among the best Phoenix DUI lawyers, led by Founding Attorney Michael Tamou and a full team of attorneys, including former prosecutors.
Phoenix DUI Defense FAQs
Quick answers to the questions we hear most.
What is the 15-minute observation rule in Arizona?
Before an evidentiary breath test, an officer must continuously observe you for 15 minutes to ensure no burping, vomiting, or regurgitation puts alcohol in your mouth. A failed or shortened observation makes the result unreliable and challengeable.
What is mouth alcohol and how does it affect a breath test?
Mouth alcohol is alcohol lingering in the mouth from burping, reflux, dental work, or breath spray. It can spike a reading far above your true blood level, which is exactly what the 15-minute observation is supposed to prevent.
Can the Intoxilyzer 8000 be wrong?
Yes. It estimates blood alcohol indirectly and depends on proper calibration, maintenance, environment, and operation. Calibration failures, radio interference, an unfit partition ratio, and operator error all produce inaccurate readings.
How do you get a breath test thrown out?
By showing the machine was not properly calibrated or maintained, the observation period failed, there was interference, or the operator was uncertified or made errors. These attacks can suppress the result or destroy its credibility.
Should I have refused the breath test?
Refusing triggers a 12-month license suspension and police usually get a warrant for blood anyway. Whether you tested or refused, the result is challengeable. Call 623-321-4699, 24/7, to review your options.
Key Takeaways
- Arizona’s Intoxilyzer 8000 estimates blood alcohol indirectly and is far from infallible.
- A required 15-minute observation guards against mouth alcohol, and it often fails.
- Calibration, maintenance, RFI, partition ratio, and operator error all inflate readings.
- Suppressing or discrediting the breath result can collapse a per se DUI charge.
- The machine’s records are decisive, and the State must be forced to produce them. Call 623-321-4699, 24/7.
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