If you’re facing a DUI (Driving Under the Influence) charge, evidence is the foundation of your case—both for the prosecution and the defense. Whether it’s a breathalyzer reading, dashcam footage, or a field sobriety test, the strength or weakness of the evidence can determine whether you’re convicted, offered a plea deal, or acquitted.
Understanding how evidence works in a DUI court case is crucial. In this article, we’ll explore the main types of DUI evidence, how it’s presented in court, and how skilled attorneys challenge or support it.
Why Evidence Matters in DUI Cases
In criminal law, the burden of proof lies with the prosecution. This means the state must prove beyond a reasonable doubt that:
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You were operating or in control of a motor vehicle, and
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You were impaired by alcohol or drugs while doing so.
To prove this, they must present credible, admissible evidence. The more compelling the evidence, the stronger their case. Conversely, weak or questionable evidence gives your defense attorney room to challenge the charges.
Types of Evidence Used in DUI Court Cases
DUI cases typically rely on a mix of physical, observational, and testimonial evidence. Here’s a breakdown:
1. Breathalyzer Test Results
One of the most common forms of evidence, breath tests measure your blood alcohol concentration (BAC). A reading of 0.08% or higher generally meets the legal definition of intoxication for adult drivers.
However, breathalyzer results can be challenged on grounds such as:
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Improper calibration
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Faulty equipment
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Lack of officer training
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Medical conditions (e.g., acid reflux)
2. Blood or Urine Test Results
In some cases, especially when drugs are suspected, police will use blood or urine tests. These are generally more accurate than breath tests but are also more invasive and can take longer to process.
Chain of custody and lab handling procedures can affect the admissibility of these results.
3. Field Sobriety Tests (FSTs)
These are physical coordination tests such as:
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Walk-and-turn
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One-leg stand
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Horizontal gaze nystagmus (eye test)
Officers use them to gauge impairment, but they’re subjective and influenced by factors like fatigue, medical issues, and even road conditions. FSTs are often challenged for being unreliable.
4. Police Observations and Testimony
The arresting officer’s account is central to the case. Their observations may include:
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Odor of alcohol
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Slurred speech
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Bloodshot eyes
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Driving behavior (e.g., swerving, speeding)
While this evidence is powerful in court, it’s also subject to bias and human error. Bodycam or dashcam footage can support or contradict these claims.
5. Dashcam or Bodycam Video
Video footage can show:
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How you were driving
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How you behaved during the stop
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How tests were administered
This is one of the most objective pieces of evidence and can support either side depending on what it shows.
6. Witness Testimony
Witnesses could include:
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Passengers
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Bystanders
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Bartenders or servers (in over-service liability cases)
Witness testimony can either support the prosecution’s timeline or the defense’s account.
7. Defendant’s Statements
Anything you say during the stop or after arrest may be used against you. Admitting to drinking—even if you believe you’re under the limit—can still strengthen the prosecution’s case.
If your Miranda rights were not read at the appropriate time, your statements may be excluded from evidence.
How DUI Evidence Is Presented in Court
During the trial, evidence is presented by:
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Prosecution, to establish guilt
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Defense, to introduce doubt or alternate explanations
Each side can:
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Submit evidence for review
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Call witnesses and experts
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Cross-examine the other party’s evidence and testimony
The judge or jury will evaluate the evidence to decide whether the legal standard for conviction is met.
How DUI Defense Attorneys Challenge Evidence
A skilled DUI attorney will closely review every piece of evidence for legal or technical weaknesses. Common strategies include:
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Filing a motion to suppress evidence obtained illegally (e.g., without probable cause)
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Challenging the accuracy of test results
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Questioning the officer’s training or conduct
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Presenting alternative explanations for physical symptoms (e.g., allergies, fatigue)
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Highlighting lack of proof of actual driving or control of the vehicle
Even small inconsistencies in the evidence can create reasonable doubt and lead to a case dismissal or acquittal.
What Happens If Evidence Is Excluded?
If a judge rules that key evidence (like a failed breath test) is inadmissible, it can weaken or dismantle the prosecution’s case. In many cases, excluding a crucial piece of evidence leads to:
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Dismissal of charges
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Reduced charges through a plea bargain
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Favorable outcomes at trial
Conclusion
Evidence is the backbone of any DUI case—and it’s often more complex than it seems. From chemical test results to eyewitness accounts, each piece plays a vital role in whether you’re convicted or cleared. But remember: no evidence is immune to scrutiny.
If you’re facing DUI charges, consult with an experienced attorney who can analyze the evidence, identify flaws, and build a solid defense. Your future could depend on how that evidence is handled.
