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OWI Breath Tests Explained

If you’re pulled over or arrested for an OWI in Iowa, the police officer may request a breath test. Two types of assessments may be administered: a preliminary breath screening test (PBT) and an evidentiary breath test (EBT). The purpose of the tests is to measure your blood alcohol concentration (BAC). The officer may use the results of the PBT to determine whether to arrest you. The prosecutor may use the results of the EBT to build a case against you and attempt to prove you are guilty of operating while intoxicated. Although a breath sample for the PBT, EBT, or both may indicate intoxication, avenues may be available to challenge results and seek a favorable outcome.

To speak with one of our Des Moines attorneys about your OWI charge, please call Branstad & Olson at (515) 329-3100 or contact us online today.

What is the Purpose of Breath Tests?

An officer might request a breath test if they suspect you have been drinking and violated Iowa’s OWI law by operating a vehicle while under the influence of alcohol or with a blood alcohol concentration of 0.08 or more. A breath test measures BAC and determines if you are at or above the legal limit.

During your OWI stop, police might request that you blow into a handheld device on the side of the road (PBT). The officer will use the results of the PBT to determine the next steps, including whether to take you into custody. Those results cannot be used in court to prove that you were driving with an unlawful BAC. They can, however, be used to show proper procedures were followed when requesting a chemical test.

If arrested, you will likely be asked to take another breath test (or a blood or urine test). The results of the evidentiary test are likely to be used at trial.

How Do Breath Tests Work?

When you drink alcohol, the substance goes through your stomach and small intestine and gets absorbed into your bloodstream. As blood flows through your body, some alcohol will move into your lungs. Thus, when you breathe out, your breath will have traces of alcohol in it.

A breath test analyzes lung air to determine your BAC. The assessment devices use various methods for the analysis, but the basic idea is the alcohol in your breath will cause a reaction with the sensors in the machine.

A breath test is not a direct measurement of the amount of alcohol in your blood. Rather, it produces an estimated BAC based on a conversion factor referred to as the partition ratio.

What Breath Tests May Be Administered?

In an OWI, two types of breath tests may be administered. The first is the PBT. This analysis is conducted in the field as part of the initial investigation. PBTs are given using a handheld device. The officer will direct you to blow into the machine to check your BAC.

The second type of breath test is the EBT. The EBT device is larger than the PBT. It is usually given at the station after an OWI arrest.

Are Breath Tests Accurate?

The results of breath tests are not 100% accurate, and PBTs are less reliable than EBTs. Although EBTs might generate more accurate results, factors including chemicals in your breath and health conditions can affect the analysis.

Can You Refuse a Breath Test?

The short answer is yes. You can refuse a breath test, but you may face consequences. If you refuse the PBT, the officer will request you submit to an EBT.

With an EBT refusal, the consequences are greater. Under Iowa’s implied consent law, if you’re lawfully arrested for OWI, you agreed to provide a specimen for a chemical analysis, including an evidentiary breath test. If you refuse the test, your license can be revoked.

Can You Challenge Breath Test Results?

You may be able to challenge the PBT or EBT results based on unlawful arrest, unlawful detention, or failure to follow the correct procedures.

Schedule a Consultation Today

Whether you refused a breath test, speak with a criminal defense attorney about your case. OWI attorneys can review your case and determine options to fight your OWI charge.

Contact our Des Moines lawyers at Branstad & Olson by calling (515) 329-3100.