What Evidence Can Be Challenged in a DUI Defense Case?

Getting pulled over and charged with driving under the influence can turn your entire life upside down in a matter of minutes. It is completely natural to feel anxious, stressed, and uncertain about what tomorrow holds for your family, your job, and your driving privileges.

As your Indianapolis criminal defense attorney, I work hard to uncover weaknesses in the state’s case so you can protect your rights and get back on your feet. I am proud to represent individuals across Noblesville, Westfield, Carmel, Fishers, and surrounding Hamilton County. If you're facing DUI charges, reach out to me today to start discussing your options.

Challenging Breathalyzer and Blood Test Results

Chemical tests are often considered the centerpiece of a prosecutor's case, but they are far from infallible. Machines break down, blood samples degrade, and human error happens far more often than most people realize. When you are looking at breath or blood test results, questioning the scientific accuracy of these numbers is a strong defensive move.

To challenge chemical testing effectively, your defense must look beyond the final number printed on the receipt. Here are several common issues that can compromise the validity of chemical test results:

• Improper calibration: Breath testing machines require regular maintenance and precise calibration logs to remain accurate over time.

• Lack of operator certification: The officer administering the test must hold valid, current certifications to run that specific equipment.

• Unobserved observation periods: Officers must monitor a driver for a set period before a breath test to prevent mouth alcohol from skewing the results.

• Fermentation in blood samples: If blood tubes are stored improperly or lack necessary preservatives, the sample can ferment and produce artificial alcohol levels.

• Chain of custody gaps: Any missing documentation showing who handled, transported, or stored your blood sample can invalidate the findings.

When any of these procedural hiccups occur, the reliability of the test drops significantly. Identifying these flaws requires a careful eye and a firm grasp of scientific standards. An experienced Indiana DUI lawyer can subpoena maintenance records and laboratory notes to highlight these mistakes for the court.

Questioning the Accuracy of Field Sobriety Tests

Field sobriety tests are designed to measure your coordination, balance, and ability to follow instructions under stress. Most people assume that failing these physical trials means automatic guilt, but that is simply not true. These roadside tests are subjective, difficult to perform even while completely sober, and frequently administered under poor conditions.

Officers must follow strict standardized guidelines established by the National Highway Traffic Safety Administration when conducting these evaluations, as several external factors can easily yield misleading results. Performing balance exercises on uneven physical surfaces like cracked pavement, gravel, or sloped roads can cause anyone to stumble regardless of sobriety.

Pre-existing medical conditions and injuries involving the back, legs, or inner ear also directly impair a driver's balance, while wearing improper footwear can make tests like the walk-and-turn nearly impossible to complete cleanly. Natural factors like high stress, fatigue, nervousness, or advanced age routinely lead to physical tremors and delayed reactions during a roadside stop.

Finally, if law enforcement provides poor instruction by failing to explain or demonstrate the test correctly, your overall performance cannot be fairly evaluated. Because these physical tests rely almost entirely on the arresting officer's personal opinion, they are easily disputed in court.

Dispute the Legality of the Initial Traffic Stop

Before an officer can ask you to step out of the car or perform any tests, they must have a valid legal reason to pull you over in the first place. The Fourth Amendment protects you against unreasonable searches and seizures, which means police cannot pull you over on a simple hunch.

Officers must articulate reasonable suspicion that a traffic violation or crime took place before turning on their emergency lights. Here are several ways to challenge the legality of the initial traffic stop:

• Unsubstantiated driving behavior: Driving slightly within your lane or briefly touching a lane line does not always constitute swerving or unsafe driving.

• Faulty police equipment: Dashcam footage sometimes contradicts an officer’s claim that you were speeding or failed to signal properly.

• Anonymous tips without corroboration: A call from another driver reporting erratic behavior is usually not enough for a stop unless the officer observes a violation directly.

• Pretextual stops: Pulling a vehicle over for a minor, non-existent infraction simply to investigate a suspicion of drunk driving is illegal.

If your defense attorney successfully proves that the officer lacked reasonable suspicion for the stop, the judge can suppress the evidence gathered during the encounter.

Work With a Criminal Defense Attorney Today

Challenging the state's evidence requires patience, attention to detail, and a deep understanding of procedural law. From chemical test flaws to improper traffic stops, there are many ways to question the prosecution's claims and protect your future.

At the Law Office of S. Neal Ziliak, I provide hands-on legal support tailored to your unique situation. As an experienced criminal defense attorney, I proudly assist clients throughout Indianapolis, Noblesville, Westfield, Carmel, Fishers, and Hamilton County. Reach out to us today to schedule your consultation and take the first step toward building your defense.