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Tempe
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Failed a Blood or Breath Test?
The Results Can Be Challenged.
Breath machines fall out of calibration, blood samples get mishandled, and officers skip steps the law requires. Our founder, Matthew Lopez, examines exactly how your blood or breath test was taken, because a flawed result can turn a conviction into a dismissal. A number on a report only counts if the process behind it holds up.
The chemical test is usually the centerpiece of an Arizona DUI case. A single number, your blood alcohol concentration, can determine whether you face a standard DUI, an extreme DUI, or a super extreme DUI, and whether you spend 10 days or 45 days in jail. Because that number carries so much weight, understanding how Arizona collects and analyzes it, and where the process can go wrong, is one of the most important things a person facing a DUI can do.
Arizona uses two main evidentiary tests: breath testing on an Intoxilyzer machine and blood testing analyzed by gas chromatography. Both are governed by strict procedures under Arizona law, and both fail more often than most people realize. This page explains how each test works, what your rights are under the implied consent law, and how faulty testing gets challenged.
Matthew Lopez Law defends DUI charges across Arizona. Contact our firm for a confidential consultation.
Under ARS 28-1321, driving on any public road in Arizona means you have already consented to chemical testing if an officer lawfully arrests you on reasonable grounds to believe you were driving impaired. This is Arizona’s implied consent law.
You can still physically refuse a test, but refusal carries its own civil penalty separate from the criminal case: a 12-month license suspension for a first refusal, and a 24-month suspension for a second refusal within 84 months. After a refusal, the officer takes your license, issues a 15-day temporary permit, and you have 15 days to request an MVD hearing to contest the suspension. Miss that window and the suspension is automatic.
A crucial distinction that trips up many drivers: not every test triggers implied consent.
The roadside preliminary breath test (PBT) is the small handheld device an officer may offer during the stop. It is used to build probable cause to arrest. Refusing the PBT carries no automatic penalty, and it is not the evidentiary test.
The evidentiary test happens after arrest, at the station, in a DUI van, or at a hospital. This is the test governed by ARS 28-1321, and refusing this one triggers the implied consent suspension. Field sobriety tests are also voluntary and carry no automatic license penalty for declining.
Arizona law enforcement primarily uses the Intoxilyzer 8000, with the older Intoxilyzer 5000 still in service in some agencies. The machine estimates blood alcohol from a breath sample using infrared spectroscopy. Arizona requires two breath samples that must agree within a set tolerance, which is one built-in reliability check.
Breath testing is convenient for police but vulnerable to error. Common problems include:
Blood testing is often called the gold standard, and Arizona courts view it as more precise, which is why agencies like Tempe and Scottsdale police have shifted toward blood draws. Blood is analyzed using gas chromatography under ARS 28-1322, and its admissibility is governed by ARS 28-1388. But blood cases have distinct vulnerabilities:
Arizona law gives you the right to obtain your own independent chemical test at your own expense after submitting to the officer’s test. You can ask to be taken to a hospital for a separate blood draw. This independent result can become powerful defense evidence if it conflicts with the state’s number. If police unreasonably prevent you from getting an independent test, the state’s evidence may be subject to challenge.
Arizona recognizes a limited right to speak with an attorney before deciding whether to submit to testing, as long as it does not delay the officer’s investigation. Requesting to call a lawyer before the evidentiary test is generally a good idea. Denial of that right can affect the admissibility of what follows.
Arizona criminalizes a BAC of 0.08 or more within two hours of driving. Because alcohol absorbs over time, the reading taken at the station may be higher than the level while driving. A forensic toxicologist can use the timing of the last drink and the absorption curve to show that the driving-time BAC was below the legal threshold, even when the station reading was above it. This “rising BAC” analysis is one of the most effective testing challenges.
Because Arizona’s penalties jump at 0.08, 0.15, and 0.20, a small change in the reading can move a case down an entire tier and cut mandatory jail dramatically. A super extreme DUI at 0.20 that gets challenged down to 0.19 becomes an extreme DUI. An extreme at 0.15 challenged to 0.14 becomes a standard DUI. This is why forensic scrutiny of the test is often the single highest-value part of a DUI defense.
Breath and blood tests look authoritative, but they rest on machines, procedures, and human operators that all make mistakes. Reviewing the calibration logs, the observation period, the blood draw, and the chain of custody is where a DUI defense often finds its strongest footing.
We serve clients in Tempe, Mesa, Apache Junction, Lake Havasu, Parker, and statewide. Payment plans available. Every interaction confidential.
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Every minute counts when you’re facing criminal charges in Arizona. Whether you were just arrested or have court next week, our team is ready to start building your defense right now. We offer free consultations and can start protecting your rights today with flexible payment plans that work for your budget.
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