How DUI Evidence Gets Challenged in Florida

By otmseo on May 12, 2026

How DUI Evidence Gets Challenged in Florida

Getting pulled over on suspicion of DUI in Florida can turn a normal evening into something that follows you for years. The flashing lights, the questions, the tests on the side of the road — it all happens fast. Many people assume that once they are arrested and evidence is collected, the case is already decided. That is not how it works.

At Jonathan B. Blecher, P.A., we have spent decades defending DUI cases in Miami and throughout South Florida. One thing we know from experience is that DUI evidence is far from bulletproof. Every piece of evidence the prosecution brings forward can be questioned, challenged, and sometimes thrown out entirely. A Miami DUI defense attorney who understands the science, the procedures, and the law can make a real difference in the outcome of a case.

Breath Test Evidence

Breath tests are one of the most common forms of DUI evidence in Florida. Law enforcement relies heavily on the Intoxilyzer 8000, the device approved for use across the state. However, these machines are not perfect.

Breath testing devices must be properly maintained and calibrated on a regular schedule. If the maintenance logs show gaps or irregularities, the results can be challenged. The officer administering the test must also follow a specific protocol, including a 20-minute observation period before the test is given. If that observation period was skipped or interrupted, the results may not be admissible.

Certain medical conditions can also affect breath test accuracy. Acid reflux, diabetes, and even certain diets can produce falsely elevated readings. Residual mouth alcohol from recent use of mouthwash or medication can skew results as well. A defense attorney who understands these factors can raise serious questions about the reliability of the numbers the prosecution is relying on.

Blood Test Evidence

Blood tests are generally considered more accurate than breath tests, but they are not immune to challenge. The way a blood sample is collected, stored, and analyzed matters enormously.

Florida law requires that blood draws follow strict chain-of-custody procedures. The sample must be properly labeled, stored at the correct temperature, and analyzed within a reasonable timeframe. If any link in that chain is broken, the integrity of the sample comes into question. Contamination, fermentation of the sample, and improper handling by lab personnel are all issues we have seen in real cases.

Additionally, the person drawing the blood must be qualified to do so. If an unauthorized individual performed the draw, or if the wrong type of antiseptic was used to clean the skin, those are grounds to challenge the evidence. Blood test results that look damning on paper can fall apart under proper legal scrutiny.

Field Sobriety Tests

Field sobriety tests are the exercises officers ask drivers to perform on the side of the road. The three standardized tests recognized by the National Highway Traffic Safety Administration are the Horizontal Gaze Nystagmus test, the Walk-and-Turn test, and the One-Leg Stand test. Officers use these to form their opinion about whether someone is impaired.

The problem is that these tests are subjective. The officer is making a judgment call based on what they observe, and that observation can be influenced by many factors. Uneven pavement, poor lighting, footwear, nervousness, fatigue, age, weight, and pre-existing physical conditions can all affect a person’s ability to perform these exercises. None of those things have anything to do with alcohol impairment.

Officers must also administer the tests according to standardized instructions. If the instructions were given incorrectly or the scoring was not done properly, the results lose their reliability. We regularly review dashcam and bodycam footage to identify exactly how these tests were conducted and whether the officer followed the required procedures.

Dashcam and Bodycam Footage

Video evidence from patrol car dashcams and officer bodycams plays an increasingly important role in DUI cases. Prosecutors often use this footage to support the officer’s account of what happened during the stop and arrest. However, this same footage can be one of the strongest tools for the defense.

In many cases, the video tells a different story than the police report. A driver who supposedly failed field sobriety tests may appear steady and coherent on camera. Speech that was described as slurred in the report may sound perfectly normal in the recording. The footage can reveal that the officer gave confusing instructions, conducted the stop improperly, or even treated the driver in a way that influenced the outcome of the encounter.

When dashcam or bodycam footage is missing or incomplete, that raises questions too. Officers are generally required to have their cameras activated during traffic stops. If footage was not recorded or was lost, a defense attorney can argue that the missing evidence should be considered in the defendant’s favor.

Witness Testimony

Witness testimony in DUI cases can come from the arresting officer, passengers, bystanders, or other individuals who observed the driver before or after the stop. While witness accounts can seem persuasive, they are often the most unreliable form of evidence.

Human memory is imperfect. Witnesses may remember events differently than how they actually occurred, especially under stressful or chaotic circumstances. A bystander who saw someone leave a bar may assume they were intoxicated without any real basis for that conclusion. An officer’s testimony about what they observed during the stop can be contradicted by video evidence or inconsistencies in their own report.

Cross-examination is one of the most effective tools for challenging witness testimony. By identifying contradictions, biases, and gaps in a witness’s account, a skilled defense attorney can significantly weaken the prosecution’s case.

Building a Strong Defense Strategy

Challenging DUI evidence is not about finding one magic argument. It is about examining every piece of the prosecution’s case and identifying the weaknesses. Sometimes the breath test was administered incorrectly. Sometimes the blood sample was mishandled. Sometimes the officer did not have probable cause to make the stop in the first place.

Each case is different, and the right defense strategy depends on the specific facts and circumstances involved. What matters is having an attorney who knows what to look for and how to use it effectively in court.

At Jonathan B. Blecher, P.A., DUI defense is a core part of what we do. Attorney Blecher is one of only a handful of lawyers in Florida who is both a Board Certified Criminal Trial Lawyer and trained in the same breath testing and field sobriety methods used by law enforcement. That combination of knowledge and courtroom experience is what allows us to challenge DUI evidence at every level.

Talk to a Miami DUI Defense Attorney Today

If you are facing a DUI charge in Miami-Dade County or anywhere in South Florida, do not assume the evidence against you is solid. There may be more room to fight than you think. Contact Jonathan B. Blecher, P.A. for a free consultation. We are available 24/7 and ready to review your case.