What Evidence Is Critical for Defending DUI Charges?
Facing a DUI charge can feel overwhelming. The possibility of losing driving privileges, paying steep fines, or even facing jail time leaves many people scared and uncertain about the future.
It’s not just about the legal consequences—it’s also about the potential impact on a person’s career, family, and reputation. Having proper evidence can make all the difference in building a strong defense.
Kathleen M. Kirchner, Attorney at Law, works with individuals who are often dealing with one of the most stressful experiences of their lives. Attorney Kirchner understands the depth of support her clients need, and she will stop at nothing to secure the outcome that best fits their future goals. Located in Anne Arundel County, Maryland, her firm serves clients throughout Anne Arundel County, Queen Anne's County, Calvert County, Prince George's County, and Howard County.
If you're facing a DUI charge, it’s important to know what evidence could play a key role in the outcome of your case.
Why Evidence Matters In DUI Defense
Evidence forms the foundation of any defense strategy. Without it, a person accused of DUI has little to challenge the prosecution’s claims. Courts rely on proof to determine whether someone was truly impaired, and defense attorneys rely on evidence to question or dispute those claims.
Every detail matters. From how a traffic stop was conducted to the accuracy of a breathalyzer test, each piece of evidence can either strengthen or weaken the case. That’s why gathering and examining evidence is one of the most critical steps in defending against DUI charges.
Police Reports and Officer Testimony
Police reports and testimony often carry significant weight in DUI cases. Officers document what they observed, why they pulled the driver over, and what actions they took. These records often serve as the prosecution’s foundation.
Essential elements from police reports include:
Reason for the stop: Officers must have had a valid basis for pulling the driver over.
Behavioral observations: Slurred speech, unsteady walking, or unusual behavior.
Timeline of events: When the stop occurred, how long the interaction lasted, and whether procedures were followed.
Details of arrest: How the officer handled field tests, breath tests, and the decision to arrest.
Challenging these records may reveal inconsistencies. If an officer’s testimony differs from what they wrote, or if their observations are subjective, this can weaken the prosecution’s argument.
Dashcam and Bodycam Footage
In today’s legal environment, video evidence often carries more credibility than written words. Many officers in Maryland use dashcams or body-worn cameras during traffic stops. Reviewing this footage can provide valuable insight into whether procedures were followed correctly.
Video evidence may reveal:
Driver’s behavior: Whether they truly appeared impaired or were acting normally.
Officer conduct: If proper procedures were followed during the stop and arrest.
Condition of the stop: Road conditions, lighting, and other environmental factors.
Tone of the interaction: Whether the driver was treated fairly and respectfully.
When video evidence contradicts a police report or supports the driver’s account, it can significantly strengthen the defense.
Field Sobriety Test Performance
Field sobriety tests are often used to justify DUI arrests, but they’re not always reliable. These tests are subjective, and results may vary based on external factors.
Factors that can affect field sobriety test results include:
Medical conditions: Balance issues, vision problems, or neurological conditions.
Environmental factors: Uneven pavement, poor lighting, or bad weather.
Nervousness: Stress from being pulled over may impact performance.
Improper instructions: If officers didn’t explain the test clearly, the results may be invalid.
Because of these weaknesses, challenging field sobriety test results is a common defense strategy. Evidence from medical records or video footage can often counter the prosecution’s claims.
Breathalyzer and Blood Test Accuracy
Chemical tests are often viewed as strong evidence in DUI cases, but they’re not foolproof. Both breath and blood tests can be challenged based on how they were conducted and whether the equipment was properly maintained.
Potential issues with chemical tests include:
Calibration errors: Breathalyzers must be regularly calibrated for accuracy.
Improper administration: If officers didn’t follow protocol, the results may be invalid.
Medical conditions: Acid reflux, diabetes, or other conditions may skew results.
Timing of the test: Alcohol levels can rise or fall quickly, impacting accuracy.
Chain of custody: Blood samples must be properly stored and handled.
Defense attorneys often request maintenance records, operator certifications, and laboratory protocols to evaluate the reliability of test results.
Witness Testimony
Witnesses can provide valuable perspectives that counter the prosecution’s version of events. Their accounts may highlight factors the police overlooked or offer explanations for a driver’s behavior.
Useful witnesses include:
Passengers: They can describe the driver’s behavior before and during the stop.
Bystanders: People who observed the stop or interaction.
Medical professionals: Doctors who can explain conditions that may affect test results.
Character witnesses: Individuals who can speak to the driver’s normal behavior and habits.
Witness testimony doesn’t always outweigh police observations, but it can raise reasonable doubt about whether the driver was impaired.
Medical Records and Health Conditions
Health records can play an important role in DUI defense. Certain medical conditions can mimic signs of impairment, leading officers to misinterpret a driver’s behavior.
Examples of medical issues that may affect DUI cases include:
Diabetes: Low blood sugar can cause slurred speech or disorientation.
Neurological disorders: Conditions like multiple sclerosis can affect balance.
Eye problems: Vision issues may impact field sobriety test performance.
Breathing issues: Asthma or GERD may affect breath test results.
Presenting medical evidence can help explain why someone appeared impaired when they were not. This type of evidence is often persuasive in creating reasonable doubt.
Procedural Errors and Legal Rights
Law enforcement officers must follow strict procedures when conducting DUI stops and arrests. If they don’t, the evidence they collect may be challenged or suppressed.
Procedural errors may include:
Lack of probable cause: Pulling someone over without a valid reason.
Improper testing protocols: Not following the required steps during breath or blood tests.
Failure to read rights: Not informing the driver of their rights upon arrest.
Unlawful detention: Keeping someone in custody for a period longer than legally justified.
Highlighting these errors can weaken the prosecution’s case and, in some situations, lead to evidence being excluded altogether.
Digital Evidence and Technology
In modern DUI defense, digital evidence can also play a significant role. From smartphone data to GPS tracking, technology may provide additional context.
Examples of digital evidence include:
Ride-sharing receipts: Proof that the driver wasn’t operating the vehicle.
Phone records: Showing calls or messages at the time of the stop.
GPS data: Tracking movements and confirming timelines.
Vehicle data: Some cars record speed, braking, and other driving behavior.
When combined with other types of evidence, digital data can create a more accurate picture of what really happened.
How All Evidence Works Together
No single piece of evidence typically determines the outcome of a DUI case. Instead, it’s the combination of multiple factors that builds a strong defense. By challenging police reports, questioning chemical tests, and presenting supportive witness testimony, defendants can raise reasonable doubt.
Each type of evidence serves a purpose. Video may contradict written reports, medical records may explain unusual behavior, and digital data may provide timelines that support the defense. Together, these elements help create a clearer picture of the situation.
Contact an Experienced DUI Attorney
Evidence plays a critical role in defending against DUI charges, and having the right defense strategy can make all the difference. Kathleen M. Kirchner, Attorney at Law, offers guidance to help clients through challenging times. Her Maryland-based firm serves clients throughout Anne Arundel County, Queen Anne's County, Calvert County, Prince George's County, and Howard County. Call today to schedule a DUI defense discussion with Attorney Kirchner.