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Top 5 Causes of False Positives for DUI Breathalyzer Tests

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If you get pulled over by a police officer at any time during the day or night, they may want to administer DUI breathalyzer tests that analyzes your blood alcohol content (BAC).

In Arizona, you can’t drive if you have a BAC of .08 or higher. If you register even a bit above the legal minimum, you will get arrested for driving under the influence (DUI).

A first offense in Arizona with a BAC under .15 is usually an expensive and inconvenient misdemeanor that results in suspension of your license for 90 days (or more, depending on the circumstances) and drunk driving classes (that may cost you money). If you blow a .15 or higher or get arrested for multiple offenses, the punishments can get much more severe.

While you have an uphill battle in front of you, a criminal defense lawyer in Phoenix can investigate any applicable DUI defenses, such as false positive DUI breathalyzer tests.

Believe it or not, a false DUI test happens rather often.

If you passed all other field sobriety tests and didn’t show blatant signs of intoxication, you may have a case.


5 Causes of False Positives for DUI Breathalyzer Tests

Knowing some of the common reasons for a false DUI test can help you select DUI defenses. Here are five common causes of false positives.

1. Officer Error or Device Error

The arresting officer is responsible for following the proper procedures associated with administering a breathalyzer. If they don’t follow guidelines perfectly, they can’t use the results against you. 

Pay close attention to the officer’s actions when they administer the breathalyzer and their timing. It’s important that the officer puts you under observation for 15 minutes before administering the test. During this time, you can’t eat, drink, or smoke. If the officer leaves you unattended, such as in the backseat of the co car, they have not completed the 15-minute observation period. 

Officers must properly maintain their devices, and it requires regular calibration. If the officer doesn’t have clear records of when they calibrated the breathalyzer, the results of the test won’t hold up in court. 

Even well-maintained devices fail or create a false DUI test. All devices have an expiration date. Even if the device didn’t extend past the expiration date, it might still fail due to age. 

2. Diet

DUI defenses may use the defendant’s diet to explain a false positive breathalyzer. 

Keto diets, in particular, tend to produce false positives more than other diets due to the way the diet utilizes the fat and energy in your body. Instead of getting energy from carbs, your body will burn fat for energy. 

During the process, the body also produces ketones and acetones. Acetones, the main ingredient found in nail polish, can exist in your breath, causing the breathalyzer to indicate a higher BAC than your accurate BAC. 

It can be difficult to prove that your keto diet contributed to your false positive. If you have subscriptions to keto diet resources from before your arrest or documentation from your doctor that references your diet, it can strengthen your case. 

3. Diabetes

Diabetes is a disease characterized by the body’s inability to regulate sugar levels in your blood.

While manageable, diabetes does cause the body to work slightly differently than other people. 

One way the body is different for people who suffer from diabetes is that it produces high levels of acetone (similar to the keto diet). 

With acetone emitting from your breath, it can cause an increased BAC reading. 

If you have diabetes, you will need proper documentation from your doctor to prove that you have the condition. 

4. OTC Medication

If you have a cold, you probably take cold medicine without truly looking at all of the ingredients. Many cold medications include alcohol. 

When you ingest the medicine through your mouth, the alcohol from the medication will remain on your breath. Even cough drops, which seem innocuous enough, can contain alcohol in them. 

While it seems almost impossible for the minuscule amount of alcohol in cough medicine or a cough drop to alter breathalyzer results to the point of a false positive, it can make the difference between blowing .06 and a .08 that will lead to your arrest. 

5. Certain Foods and Drinks

You don’t necessarily have to drink alcohol to cause your BAC level to rise, thanks to their reactions in the body. 

It can also increase when you eat the following foods:

  • cinnamon rolls
  • fermented fruit
  • bread
  • hot sauce

Since you probably didn’t know that these foods can alter your BAC, you probably didn’t consider it as a cause during your arrest. However, that last piece of bread at dinner might have actually hurt you in your arrest. 

You may also get a false positive breathalyzer if you recently used mouthwash, especially if the mouth wash contains alcohol.

However, many of us carry mouthwash in the car for meetings and dates. If you happen to use mouthwash before you head home, it can produce a false DUI. 

Avoid a false negative caused by foods by waiting to drive until you’ve had plenty of time to digest your food, especially if you’ve had a glass of wine or two.


What to Do After a False Positive?

What should you do if you suspect a false positive?

Don’t try to make up reasons for the false positive on a whim. At this point, you will likely get arrested no matter what. 

If anything, mentioning that you fear a false positive may only cause the police to perform a second test, giving them more ammunition in their case against you. 

Go through with the arrest process cordially and limit the details you provide about the incident until you talk to a DUI lawyer in Phoenix. 

Always ask to speak to an attorney and call one when you are given the opportunity.  Invoke your right to remain silent.

After you are released, here are some tips on how to handle the situation.

1. Examine Why You Were Pulled Over

A police officer must have reasonable suspicion to pull you over. 

Some examples of valid reasonable suspicion include speeding, swerving, driving too slowly, or even a broken headlight or taillight. 

Police officers also have the right to set up DUI checkpoints, which gives them the opportunity to stop people at will. 

Most officers provide a passable reason for pulling you over, but you may be able to catch the officer in inconsistencies when you dive into the details. 

If you can prove that the officer had no reason to pull you over in the first place, the breathalyzer test afterward is irrelevant. 

2. Analyze the Field Tests and Arrest

Think about what happened with the police officer in detail. 

How long did the officer wait before administering your test? Were you under the officer’s observation the entire time? Did you do anything, such as chew a mint or cough drop, that may alter the results of the breathalyzer?

What field tests did you do, and how did you perform? What were the conditions like during the arrest?

The smallest detail can open the door to a possible DUI defense. 

3. Obtain All Documentation and Video Possible

You may have access to video of your arrest if you have a camera in your car or got arrested near a building with a security camera. 

You should also gather all documentation you receive after the arrest. You will want to see the officer’s perception of the events so that you can see where your stories match. 

4. Stay Off of Social Media

Social media can be a useful tool when communicating with long-distance family, but it doesn’t usually contribute to a great DUI defense. 

Even if you have a private account, the prosecution may use social media against you in your DUI case in Phoenix. 

The worst thing you can do is post too much information regarding the situation on social media. You don’t want to appear inconsistent. 

Furthermore, you don’t want the prosecution to see pictures and videos of you drinking, as it can look bad to the judge. 

Avoid posting pictures out at clubs and parties. You should also avoid the topic all together when posting on social media.

5. Hire a Lawyer

DUI defenses can get rather complicated, especially when proving a false positive. You also have a lot to lose if things don’t go in your favor. 

Hire a DUI defense attorney who can answer your questions and help you build a defense. 

Hiring a lawyer shows the state court that you take the incident seriously. The lawyer also has the knowledge to pick the most effective defense. 

Hire a lawyer immediately after your arrest. Limit the information you provide to the police until you talk to your attorney. Always tell your attorney the truth about the incident. If you leave out important details, it can negatively impact your case.


Did you get a DUI in Phoenix? We at Gurion Law can help. 

We all make mistakes (sometimes even repeated mistakes). However, you don’t deserve to be punished for a false positive. 

Contact Gurion Legal today to schedule a free consultation where you can learn more about false positives and whether it’s the best DUI defense for your case. We handle misdemeanor DUI, aggravated DUI, and super DUI charges.

We know the Arizona DUI laws in excruciating detail, and if there’s a way to discredit the breathalyzer results, we will find it.


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