Key Evidence in a DUI Case

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Key Evidence in a DUI Case

When a DUI (driving under the influence) case is being built against a driver, law enforcement and the prosecutor will rely on specific types of evidence in their attempt to secure a conviction. Here, we consider the primary types of evidence that may be used against a DUI suspect to pursue a DUI conviction.

Testimony from the Arresting Officer

For starters, the arresting officer will probably testify about the circumstances surrounding the police stop, field sobriety tests, the PAS test (preliminary breath test), and the DUI arrest.

One key factor will be the defendant’s driving behavior and the specific actions that led to the police stop in the first place.

Law enforcement must have probable cause to pull a driver over, such as running a red light, swerving out of a lane, driving too slowly or a traffic violation. The police can’t sit outside of bars and wait for patrons to drive away, or stop people for no good reason.


The officer may testify regarding the driver's behavior and appearance. Was the driver rude or belligerent? Did the driver stumble or fall when they got out of their vehicles? Were they slurring their words? Was there a strong odor of alcohol on the driver’s breath?

The prosecution is trying to establish that the driver was intoxicated, thus warranting the administration of field sobriety tests.

Field Sobriety Tests (Roadside Tests)

Many people are not aware that they are not required to submit to the field sobriety tests, and that there is no penalty for politely refusing. But still, plenty of people don’t know this so they take them anyway.

If the driver submitted to field sobriety tests, the officer who administered the tests may offer testimony regarding the driver's performance. Tests like the walk-and-turn, horizontal gaze nystagmus, or one-leg stand are administered to check a driver's balance, coordination and ability to follow instructions.

In addition to the officer's testimony, any video surveillance of these tests captured on the officer’s dash cam or body camera will likely be submitted as evidence.

Incriminating Statements from the Driver

“Why yes officer, I had a couple of drinks at the bar, but I’m fine to drive.” If a driver says something to this effect, it can and will be used against them.

A driver who answers "yes" to the question, "Have you been drinking?" is falling into the officer’s trap. It is important to remember that you do not have to submit to questioning and that you can demand to have your attorney present during formal questioning after a DUI arrest.

Results of Chemical Tests

If a driver submits to a breathalyzer or blood test, the results may provide the foundation for the prosecuting attorney's case. If a driver submits to a chemical test that shows a blood alcohol concentration (BAC) of .08% or greater, the prosecution will attempt to secure a conviction based on this result.

Breath and blood tests may be unreliable or improperly administered, thus, an experienced DUI attorney will thoroughly investigate every aspect of DUI testing to determine how to devalue results.


The prosecution may also show other applicable physical evidence, such as an open container of alcohol that was found in the driver's vehicle, photographs of an accident scene if the driver was involved in an accident, witness testimony, etc.

Are you interested in learning more about the evidence used in DUI cases and how an Orange County DUI lawyer can challenge such evidence? If so, call the Law Offices of Virginia L. Landry for a free consultation. We will be happy to answer your questions and to address your concerns.

Categories: DUI, DUI Defense
  • Board Certified Expert

    in DUI Defense

    Chosen as a “Top DUI Attorney” in Orange County & rated 10 out of 10 by Avvo.

    Meet Virginia L. Landry
  • Answers to All of

    Your Questions

    Visit our FAQ page to get answers to some of the most common questions.

    Read Common Questions
  • Get Help

    Immediately

    Don’t wait, time is of the essence. Contact us now for a free case evaluation.

    Get Started Today

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