DUI/DWI Law

Breathalyzer Test FAQ

If you are pulled over on the suspicion of driving under the influence of alcohol, the officer may ask you to consent to a Breathalyzer test. This test will read your blood alcohol content (BAC). These tests can pick up a trace concentration of alcohol and determine the level of alcohol in your body.

The officer who stops you will use the results of the test and with other evidence, to determine whether you are impaired beyond the legal limit. It is important to point out you can still be charged with DUI regardless of the results of a portable breath test. Any presence of alcohol can lead to impaired driving, and impaired driving can also happen with other substances, such as illegal drugs, in your system.

What Methods Do Officers Use to Determine Your BAC?

There are several methods that a police officer can use to determine your blood alcohol content:

  • A Breathalyzer test measures the amount of alcohol in your breath, and that number is converted into an estimate of your BAC. This is the most common type of test that happens during traffic stops.
  • Field sobriety tests indicate whether you are impaired by alcohol. While there is no way to measure an accurate BAC level from such tests, they do indicate if you are having trouble walking, are slurring your speech, or are otherwise showing signs of impairment.
  • Blood tests occur at a police station, jail, or hospital after you've been arrested on suspicion of DUI. Blood tests directly measure how much alcohol is in your system. These tests are very accurate. However, the U.S. Supreme Court has ruled that police must obtain a warrant before a blood test.
  • Urine tests can take place at a police station or jail. They are very accurate tests, but laws are unclear about needing a warrant first.

These tests all give a comprehensive look at your body's current alcohol level. Things like alcohol vapor or residual mouth alcohol will only show on a breath test, and they can cause a false positive.

Alcohol consumption over a period of time will show on a blood or urine test. These tests can typically detect alcohol 24-48 hours after alcohol consumption.

Just How Does a Breath Test Work?

A Breathalyzer, or any breath alcohol tester, involves blowing into a small tube. The volume of air that passes through the tube is collected by a machine that analyzes its contents.

In a matter of seconds, a police officer or anyone else administering the test can gain a rough estimate of how many grams of alcohol are in your system.

How Accurate Are Breath Tests?

While less accurate than a blood or urine test, breath testing is generally considered accurate enough to use when criminal charges are filed.

During your trial, the breath test results can be used as evidence that you were intoxicated at the time of the traffic stop.

Is it Possible to Challenge Breath Test Results in Court?

There are many ways to challenge the results of a breath test in court. First, it may be possible to argue that the machine used in a particular test was not manufactured properly or certified by the manufacturer. Another challenge that is sometimes successful is directed at how the machine was calibrated.

It may also be possible to challenge the results of the test because it was not conducted according to state law. For instance, Pennsylvania law requires that an officer conduct two tests 10 seconds apart from each other.

Another argument could be that the test was flawed because too much time had passed between the time you started driving and the time of the test. For some people, their BAC can actually continue to increase after they stop drinking.

Are Smaller Consumer Models of Breathalyzers Accurate?

In general, portable units manufactured and sold for personal use are almost as accurate as those used by the police. However, most companies that make or sell these devices advise people not to solely rely on them to decide if they are impaired or not.

This is because age, gender, and personal tolerance level also play a role in whether they are too drunk to drive. These portable devices might be good tests for alcohol before you drive home, but there are still risks involved.

Should I Get Help From a DUI Attorney?

If you are facing charges of driving under the influence, you should consider seeking a free consultation from an attorney. A conviction could mean penalties like using an ignition interlock device on your vehicle, driver's license suspension, loss of driving privileges, jail time, attending an alcohol treatment program, or going to rehab. There are defense strategies available to you depending upon the particular circumstances of your case, beginning with whether the law enforcement officer had reasonable suspicion to make the initial traffic stop.