Criminal Law

What Are “Breathalyzer” Tests?

By Joshua Egan, Attorney
Learn about the breath tests that police use to measure BAC in DUI investigations.

Updated May 24, 2016

To many law enforcement officers, breath-test devices are the preferred tool for measuring the amount of alcohol in a driver’s body. These devices (sometimes called “breathalyzers”) are often portable—meaning they can be used roadside—and provide instantaneous results. Breath tests are popular also because they’re less invasive than blood and urine tests, which can also be used to measure blood alcohol concentration (BAC).

Preliminary Alcohol Screening (PAS) and Evidential Breath Test (EBT) Devices

There are two types of breath measuring instruments used in DUI cases: “preliminary alcohol screening” (PAS) devices and “evidential breath test” (EBT) machines.

(For a discussion of some of the factors that affect the accuracy of breathalyzer tests, see How Accurate Are “Breathalyzers”?)

PAS Tests

PAS devices are sometimes called “portable breath tests” (PBT). These are small, handheld machines that police use during DUI stops to detect the amount of alcohol on the suspect's breath. Police usually use PAS tests to determine whether there’s probable cause to make a DUI arrest. The results of PAS tests, however, typically aren’t accurate enough for prosecutors to use in court as evidence of the driver’s BAC.

(For more on PAS devices, see What is a Preliminary Alcohol Screening (PAS) Test?)

EBT Tests

Though EBTs aren’t perfect, they’re generally more accurate than PAS tests. They’re also usually admissible in court because of their reliability. Indeed, it’s common for prosecutors to use EBT results to prove BAC in DUI trials.

EBT devices are often larger and more costly than PAS machines. In Georgia and Texas, for example, officers use a big, stationary machine called the “Intoxilyzer 5000” to measure the BAC of DUI suspects. Officers in states like these must transport a suspect to the station for this kind of testing. Officers in other states have portable EBT devices that, like PAS machines, can be used roadside to determine BAC.

(For more on EBT machines, see What is an Evidential Breath Test (EBT)?)

Get in Touch With an Attorney

DUI laws differ by state. And the facts of a given case have everything to do with the outcome. If you’ve been arrested, get in touch with an experienced DUI attorney. A local lawyer can explain the relevant law and procedure to you.

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