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How is a roadside breath test different than a breath test in the station?

A roadside breathalyzer test is not the same as a chemical breath test taken after a drunk driving arrest. The handheld breath testing device is generally less accurate than the police station machines. A roadside breath test is generally not mandatory and the results cannot always be used as evidence of the driver's blood-alcohol level.

A breath test after an arrest is required or the driver could have their license suspended for refusing a breath test. The results of the chemical test after an arrest can be used as evidence in court to show the driver was over the legal limit.

It is important to understand the difference between a roadside breath test and a breath sample at the police station. However, these tests can be challenged to show they were unreliable or tainted to get charges dropped or reduced. If you are arrested for a DUI in Fremont or anywhere in the East Bay, contact the experienced California DUI lawyer Lynn Gorelick today.

Roadside Breath Testing in California DUIs

When the police stop a driver and suspected the driver might be impaired, they need to have probable cause to make an arrest. This could include statements by the driver that he or she had been drinking, evidence of an open container in the car, or a preliminary breath test.

The roadside breath test is known as a preliminary alcohol screening (PAS) device. The benefit of a PAS device for police is that these are small, handheld devices which they can quickly use to get an estimate of the driver's blood alcohol content (BAC). If the device registers at about 0.08% or higher, the police may have the probable cause they need to make an arrest.

The negative for drivers is that these devices can give improper readings or false positives that lead to an arrest for drivers who are under the limit. Additionally, even if the device shows a BAC below the legal limit, the police may still decide to make an arrest.

Roadside Breath Testing is NOT Mandatory in California  

Some drivers may be required to give a roadside breath sample, including drivers who are under the age of 21 and drivers who are on DUI probation. However, for most drivers, PAS breath tests are not mandatory. Many drivers may decide to refuse to submit to these tests because they are not always reliable and could be used against the driver to justify an arrest.

There are no penalties for refusing a PAS test for drivers who are not required to submit a breath test. The police officer may try to get a driver to give a breath because it generally makes their job easier. However, these tests give inaccurate results for things like:

  • Cough Drops
  • Cold Medicine
  • Mouthwash
  • Asthma Inhalers
  • Pain Relief Gel
  • Chewing Gum
  • Burping
  • Improper Calibration

Chemical Tests After a California DUI Arrest Are Required

If the police officers have placed you under arrest then a chemical test is required. Refusing to submit to a chemical test in California after a DUI arrest can result in a suspended license, even if you are never charged or convicted of a DUI. The suspension period depends on your prior DUI history.

Chemical Test Refusal

Driver's License Suspension

1st Refusal

One Year

Refusal on 2nd DUI Offense in 10 Years

Two Years

Refusal on 3rd DUI Offense in 10 Years

Three Years


In addition to the DMV suspending your license, if you are convicted of a DUI, you may face enhanced DUI penalties for refusing to submit a chemical breath test sample. This includes additional time in jail and extended DUI school for a first DUI offense.

Implied Consent Law in California

Many drivers are unaware that they have already agreed to chemical testing in DUI arrests just because they drive in California. You may not have explicitly agreed to this, but under California law, you are considered to have given implied consent to chemical testing in exchange for the right to drive on California roads.

Chemical Test Results Are Not 100% Reliable

Chemical test results are not 100% reliable. Just because the chemical tests show you were above the limit does not mean that you are guilty. There may be problems with the testing device, calibration, cleaning, and maintenance, or the way the police officer operated the machine. There can also be a number of medical reasons why the test showed an elevated BAC that are unrelated to drinking alcohol.

Talk to your California DUI lawyer about your case. You may have a number of defenses available to challenge the initial arrest or chemical test results. If you have been arrested on suspicion of drunk driving in Alameda County or anywhere in the East Bay, contact East Bay DUI lawyer Lynn Gorelick today.

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