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DUI Defense Strategies: Probable Cause for Arrest

Posted on in DUI Defense

IL DUI lawyerBefore the police can legally arrest someone for driving under the influence of drugs or alcohol (DUI), the police must have “probable cause” to believe that the person actually committed the crime. Probable cause consists of specific facts or observations made by the police.

This is not the same as proving the person “guilty beyond a reasonable doubt,” which is the standard for actually convicting someone and punishing them for the crime.

Lack of Probable Cause for an Arrest Is a Common Defense Strategy

The police must be able to state clearly their basis, or probable cause, for arresting a person on the charge of DUI. If the probable cause is deemed legally insufficient, the arrest can be ruled invalid and the charges would have to be dropped.

So, what constitutes probable cause to arrest someone for DUI?

Probable Cause for a DUI Arrest

The probable cause for a DUI arrest typically involves some combination of officer observations, field sobriety tests, and a portable breathalyzer test which measures a person’s blood alcohol concentration (BAC) at roadside.

Ways to Challenge Probable Cause for a DUI

Field Sobriety Tests: An officer can request that a driver perform field sobriety tests, but the driver is free to refuse and there is no legal penalty for refusal. If the driver does consent and fails the tests, then that failure is sufficient “probable cause” for a DUI arrest. A defense attorney would want to interview the accused person and the arresting officer, and view any audio or video recordings, to see if the tests were conducted properly; if not, those tests could be ruled invalid. That could leave the police without the necessary probable cause for the arrest, and the arrest could be thrown out.

Roadside Breathalyzer Test: An officer can request that a driver consent to a portable BAC test (PBT) at roadside, but the driver is free to refuse with no legal repercussions. If the driver does consent, then the PBT results may be used as probable cause for a DUI arrest. Again, a defense attorney would investigate to see if there was anything improper about the way the PBT was conducted; if so, the PBT result could be thrown out, eliminating another element of probable cause for the arrest.

Note that the pre-arrest PBT is different from the post-arrest evidentiary BAC testing. PBT results can be used as probable cause for an arrest, but are not admissible as evidence in court. The evidentiary BAC test is done at a police station or hospital, and specific procedures must be followed in order for the results to be admissible in court. A driver can refuse to submit to an evidentiary breathalyzer test, but there is a statutory penalty for refusing (a longer driver’s license suspension) and the police can get a warrant to force a driver to submit to a blood test.

Officer Observations: Without field sobriety tests or a PBT, an officer must be able to cite specific observations that, taken together, meet the standard of probable cause. Examples include a smell of alcohol on the person’s breath, open alcohol containers in the vehicle, slurred speech, how the person responded to the officer’s questions (e.g., admitting how many drinks they had), and erratic driving. Upon attorney interrogation and review of police dashcam video, however, such observations can often be called into question.

Advice from an Experienced DuPage County DUI Defense Attorney

If you or a loved one has been charged with DUI, contact an experienced Oak Brook DUI defense lawyer without delay. Call McMahon Law Offices at 630-953-4400 for a free consultation. We are available for weekend and evening appointments.





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