Potential Defenses Against California DUI Charges
Being arrested for driving under the influence (DUI) can be one of the most stressful experiences a person faces. A conviction can lead to steep fines, driver’s license suspension, mandatory DUI classes, probation, and even jail time—consequences that can affect employment, finances, and personal freedom. But a DUI charge is not the same as a conviction. California law requires prosecutors to prove their case beyond a reasonable doubt, and numerous defenses may be available depending on the facts of the stop, the testing process, and your medical condition.
Whether the case involves alcohol, prescription drugs, or alleged impairment by cannabis, an experienced criminal defense attorney can identify weaknesses in the prosecution’s evidence and fight to have charges reduced or dismissed. Below are some of the most common and powerful defenses used in California DUI cases. In San Bernardino County, reach out to Attorney John D. Lueck for help from a skilled and experienced Rancho Cucamonga DUI defense lawyer.
Challenging Breathalyzer Reliability
Breathalyzer results often form the backbone of the prosecution’s case. Under California Vehicle Code § 23152, driving with a blood alcohol concentration (BAC) of 0.08% or higher can lead to DUI charges. But breath testing devices are far from infallible.
Machines Must Be Properly Calibrated
California regulations require breath-testing devices to undergo regular accuracy checks. If the machine used in your case was overdue for calibration, improperly maintained, or used by an untrained operator, the results may be unreliable. Records of the machine’s maintenance history can reveal defects or missed inspections.
Partition Ratio Variability
Breathalyzers use a standardized “partition ratio” to convert alcohol in the breath into an estimated blood alcohol level. The problem? Human bodies don’t all follow the same ratio. Factors such as body temperature, breathing pattern, and individual physiology can cause breath test results to deviate significantly from actual BAC.
Mouth Alcohol Contamination
Residual alcohol in the mouth can cause falsely elevated readings. This may occur due to:
- Recent use of mouthwash or breath sprays containing alcohol
- Acid reflux or GERD causing stomach alcohol to rise into the mouth
- Dental work that traps small amounts of alcohol
California officers are required to observe a driver continuously for 15 minutes before administering a breath test. If they fail to do so, contamination becomes a strong defense.
Poor Operator Technique
Breathalyzers must be used exactly as instructed. If the officer rushed the test, didn’t ensure a deep-lung breath sample, or took only one sample instead of two, the results may not meet legal standards.
Unreliability of Field Sobriety Tests
Field sobriety tests (FSTs) are used to establish probable cause for arrest, but they are not scientific. Out of the dozens of physical and cognitive tasks officers sometimes use, only three have been standardized by the National Highway Traffic Safety Administration (NHTSA). These three are:
- Horizontal Gaze Nystagmus (eye test)
- Walk-and-Turn
- One-Leg Stand
Even these standardized tests are only accurate when administered under strict conditions, and officers frequently deviate from protocol.
Environmental and Physical Factors
Uneven pavement, poor lighting, loud traffic, or bad weather can make FST performance look like impairment even when the driver is sober. Likewise, many physical conditions can affect performance, such as:
- Inner ear or balance disorders
- Leg, back, or foot pain
- Weight or age-related mobility issues
- Anxiety or nervousness during the stop
None of these conditions indicates alcohol impairment, but they can lead officers to misinterpret results.
Officer Subjectivity
Officers often interpret FST performance according to their own expectations. A driver who is nervous, confused, or unsure of instructions may appear intoxicated even when they are fully sober.
Medical Conditions That Can Mimic Impairment or Affect BAC Readings
Not all signs of alleged impairment come from alcohol or drugs. Many medical issues can produce symptoms similar to intoxication or cause inaccurate test results.
Diabetes and Hypoglycemia
Low blood sugar can cause slurred speech, confusion, shakiness, and poor coordination, symptoms commonly associated with intoxication. Diabetics in ketosis may also produce acetone on their breath, which certain breathalyzers can misinterpret as alcohol.
GERD, Acid Reflux, and Heartburn
These conditions can bring alcohol vapors from the stomach into the mouth, falsely elevating breath test readings. If an officer does not follow the mandatory observation period, the test becomes even more unreliable.
Neurological or Musculoskeletal Conditions
Issues such as multiple sclerosis, stroke history, or chronic injuries can affect gait, balance, and speech, which officers sometimes mistake for intoxication.
Medication Interactions
Certain prescription medications, even when taken as directed, can cause drowsiness, pupil changes, or slowed reactions. Others can interact with alcohol in ways that complicate testing accuracy.
Procedural Defenses: When Police Make Legal Mistakes
Even if all tests were technically accurate, the case may still be flawed if police violated your rights or failed to follow proper procedure.
Lack of Reasonable Suspicion for the Traffic Stop
Police must have a lawful reason to stop you. If they pulled you over without a valid basis, such as a claim you were “swerving” that is not supported by evidence, the entire case may be thrown out.
Lack of Probable Cause for Arrest
Officers must establish probable cause before making a DUI arrest. Weak field sobriety test results, subjective observations, or vague descriptions of “red eyes” or “odor of alcohol” might not meet the legal threshold.
Failure to Follow Title 17 Requirements
California’s Title 17 regulations govern how blood and breath samples must be collected, stored, and analyzed. Errors such as improper labeling, contaminated samples, or chain-of-custody issues can invalidate results.
Failure to Administer an Implied Consent Warning
Drivers must be advised of the consequences of refusing a chemical test after arrest. If police fail to give the required warning, test results or refusals may be inadmissible.
How a Skilled Criminal Defense Attorney Can Help
DUI cases are technical and scientific, and small details can dramatically affect the outcome. An experienced criminal defense lawyer like John D. Lueck knows how to uncover problems with the stop, the arrest, the testing procedures, and the prosecution’s evidence.
Attorney Lueck can:
- Review dashcam and bodycam footage
- Obtain maintenance and calibration records for breath-testing devices
- Challenge the legality of the traffic stop
- Question whether officers complied with NHTSA and Title 17 requirements
- Consult with toxicology experts
- File motions to suppress evidence
- Negotiate for charge reductions, alternative sentencing, or dismissal
Every DUI case is different, and the right defense strategy requires a careful analysis of the facts. What may appear to be a strong case against you can often be weakened or completely dismantled once the evidence is examined closely.
Protect Your Future—Get Legal Help Immediately
A DUI charge can have long-lasting consequences, but the right legal representation can make all the difference. If you have been arrested for DUI in Rancho Cucamonga or anywhere in San Bernardino County, Attorney John D. Lueck is ready to defend your rights and challenge the evidence against you. The sooner you seek legal representation, the stronger your defense will be.
Contact Attorney John D. Lueck today and learn how an experienced California DUI defense lawyer can help you move forward.
