Breathalyzer Defense in Phoenix: Can You Challenge the Test Results in Court?

02|2025

Introduction

If you’ve been arrested for DUI in Phoenix, chances are a breathalyzer test played a significant role in your charges. Law enforcement relies heavily on breathalyzer results to establish whether a driver was over the legal limit. However, these tests are not foolproof. They can produce inaccurate readings due to various factors, including device malfunctions, improper administration, and even medical conditions.

Challenging a breathalyzer test in court can be a critical part of your DUI defense strategy. If your attorney can prove the results were flawed, your charges may be reduced or even dismissed. This article explores how breathalyzer tests work, the potential weaknesses in their accuracy, and the strategies an experienced DUI lawyer can use to fight your case.

How Breathalyzer Tests Work in DUI Cases

A breathalyzer measures the alcohol content in your breath to estimate your blood alcohol concentration (BAC). In Arizona, the legal limit for most drivers is 0.08%, while commercial drivers have a lower threshold of 0.04%. For drivers under the age of 21, any detectable alcohol level can result in a DUI charge under the state’s zero-tolerance policy.

Law enforcement officers typically administer breathalyzer tests in two ways:

• Preliminary Breath Test (PBT) – A handheld device used during traffic stops to determine whether a driver might be impaired. PBT results are not always admissible in court.
• Evidentiary Breath Test (EBT) – A more advanced test conducted at the police station using a stationary device. These results are considered more reliable and are typically used as evidence in court.

While breathalyzers are widely used, they are far from perfect. There are multiple reasons why a test result could be inaccurate, making it essential to scrutinize every aspect of how your test was conducted.

Common Factors That Can Lead to Inaccurate Breathalyzer Results

Many people assume that breathalyzer results are infallible, but the truth is that numerous factors can lead to errors. Below are some of the most common reasons why a breathalyzer reading might not be accurate.

1. Improper Calibration and Maintenance

Breathalyzer machines require regular calibration and maintenance to function correctly. If the device has not been properly calibrated, it may produce incorrect BAC readings. Arizona law requires that breathalyzers be checked and maintained regularly. If records show that the device was not properly serviced, your attorney may be able to challenge its accuracy in court.

2. Officer Error in Administering the Test

Breathalyzer tests must be conducted according to strict guidelines. If the officer administering your test failed to follow proper procedures, your results could be invalid. Common mistakes include:

• Failing to observe the driver for at least 15 minutes before the test to ensure they haven’t consumed food, drink, or gum
• Not instructing the driver correctly on how to blow into the device
• Using a device that was not recently calibrated

If procedural errors occurred during your breath test, your attorney could argue that the results should be thrown out.

3. Medical Conditions That Affect Breathalyzer Results

Certain medical conditions can interfere with breathalyzer readings, leading to false positives. These include:

• Acid reflux or GERD – Stomach acid can travel up into the esophagus and mouth, contaminating the breath sample with alcohol from the stomach rather than the bloodstream.
• Diabetes – Diabetics sometimes produce ketones, which can be mistaken for alcohol by breathalyzer devices.
• Hypoglycemia – Low blood sugar can cause symptoms similar to intoxication, leading officers to assume impairment when none exists.

If you have a medical condition that could have affected your test results, your lawyer may present medical evidence to challenge the breathalyzer reading.

4. Residual Mouth Alcohol

Breathalyzers are designed to measure deep lung air, not alcohol lingering in the mouth. However, residual alcohol from recent drinking, mouthwash, breath fresheners, or even some medications can lead to an inflated BAC reading.

Law enforcement officers are required to wait 15-20 minutes before administering a breath test to reduce the likelihood of residual mouth alcohol affecting the results. If this waiting period was not followed, your attorney could use it as a defense.

5. Interference from Other Substances

Breathalyzers can sometimes misinterpret substances in a person’s breath as alcohol. These include:

• Certain medications, including asthma inhalers
• Mouthwashes and breath sprays that contain alcohol
• Fumes from chemicals, such as paint or gasoline, which can be inhaled and absorbed into the bloodstream

If you were exposed to any of these substances before your breath test, your lawyer might be able to challenge the results.

Legal Strategies to Challenge a Breathalyzer Test in Court

An experienced DUI attorney can use several strategies to challenge breathalyzer evidence in court. Below are some of the most effective ways to cast doubt on the test results and potentially have your charges reduced or dismissed.

1. Requesting Maintenance and Calibration Records

One of the first steps your attorney will take is requesting maintenance and calibration records for the breathalyzer device used in your case. If there is evidence that the device was not properly maintained, the test results may be invalid.

2. Cross-Examining the Arresting Officer

During court proceedings, your lawyer can cross-examine the arresting officer to uncover errors in how the breath test was conducted. If the officer did not follow proper procedures, your attorney can argue that the results should not be admissible.

3. Challenging the Test as Unreliable

Your attorney may call in expert witnesses, such as forensic toxicologists, to testify about the scientific flaws in breathalyzer technology. These experts can explain how external factors like medical conditions, diet, and device malfunctions can lead to false positives.

4. Presenting Alternative Evidence

If your breath test results are questionable, your lawyer may present alternative evidence to challenge the prosecution’s case. This could include:

• Surveillance footage showing you were not impaired
• Witness testimony from people who were with you before the arrest
• Medical records demonstrating conditions that could have affected the test results

5. Arguing Violations of Your Rights

If the police violated your constitutional rights during the traffic stop or arrest, your attorney can file a motion to suppress evidence. If successful, this could lead to the breathalyzer test results being excluded from the case.

Conclusion

A breathalyzer test is not always as reliable as law enforcement claims. There are multiple factors that can lead to false or inflated BAC readings, including device malfunctions, medical conditions, officer errors, and environmental influences.

If you’ve been charged with DUI in Phoenix based on breathalyzer results, you don’t have to accept them as fact. An experienced DUI defense lawyer can investigate your case, challenge the validity of the breath test, and work to get your charges reduced or dismissed.

Challenging a breathalyzer test can make a significant difference in your case’s outcome. If you’re facing DUI charges, consult a skilled attorney as soon as possible to explore your legal options.