Defenses to DUI/DWI Charges
A DUI (Driving Under the Influence) or DWI (Driving While Intoxicated) charge is serious, but it is not an automatic conviction. There are numerous legal defenses that an experienced attorney can use to challenge the prosecution's case.
Challenging the Traffic Stop
Police must have reasonable suspicion to pull you over. If the stop was unlawful, all evidence obtained afterward may be suppressed. Invalid reasons for a stop include:
Stopping based solely on an anonymous tip without corroboration
Racial profiling or stopping a driver based on appearance
Stopping a vehicle leaving a bar without observing any traffic violations
Using a broken taillight as a pretext for a DUI investigation
If a court finds the stop was unconstitutional, the entire case may be dismissed.
Challenging Breathalyzer Results
Breathalyzer machines (like the Intoxilyzer and Draeger) are not infallible. Common challenges include:
Improper Calibration
Breathalyzer machines must be calibrated regularly (typically every 31 days or after a set number of uses)
If the machine was not properly calibrated, results may be inaccurate
Defense attorneys can subpoena calibration and maintenance records
Operator Error
The officer administering the test must be properly trained and certified
The officer must observe the subject for 15-20 minutes before the test to ensure they don't eat, drink, vomit, or belch (which can affect results)
Failure to follow proper procedures can invalidate the results
Interfering Substances
Mouthwash, breath spray, or denture adhesive containing alcohol can produce false positives
Certain medical conditions, including acid reflux (GERD), can cause alcohol from the stomach to register in the breath
Some medications can interfere with results
Environmental factors (paint fumes, gasoline) can affect readings
The Rising BAC Defense
Alcohol takes time to absorb into the bloodstream — typically 30 minutes to 2 hours after your last drink. The rising BAC defense argues that:
Your blood alcohol concentration was below the legal limit while you were driving
By the time you were tested (often 30-90 minutes later), your BAC had risen above the limit
What matters legally is your BAC at the time of driving, not at the time of testing
This defense is most effective when:
You consumed alcohol shortly before driving
There was a significant delay between the stop and the breath test
Your BAC was close to the legal limit (0.08%)
Challenging Field Sobriety Tests
Standardized Field Sobriety Tests (SFSTs) include the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand. These tests are subjective and can be challenged:
Physical conditions — injuries, obesity, age, inner ear disorders, or neurological conditions can affect performance
Environmental conditions — uneven ground, poor lighting, bad weather, heavy traffic can impair performance
Improper administration — officers must follow standardized procedures exactly
Nervousness — anxiety during a police encounter can mimic signs of impairment
Clothing — high heels or restrictive clothing can affect balance tests
Even under ideal conditions, the National Highway Traffic Safety Administration's own research shows SFSTs are only 65-77% accurate when properly administered.
Challenging Blood Test Results
Blood samples must be drawn by a qualified person using proper procedures
The sample must be properly stored to prevent fermentation (which can increase BAC)
Chain of custody must be maintained — any break can raise reasonable doubt
The defendant has the right to independent testing of the blood sample
Other Defenses
Necessity — you drove to avoid a greater harm (e.g., fleeing a dangerous situation)
Duress — someone forced you to drive while impaired
Involuntary intoxication — you were drugged without your knowledge
No driving — the prosecution must prove you were actually operating the vehicle
Disclaimer: This guide is for informational purposes only. DUI/DWI laws and penalties vary by state. If you are facing DUI charges, consult a criminal defense attorney immediately.