A blood number can look like the end of the road. It rarely is. In a Florida DUI, that number has to survive four separate checkpoints before a jury should rely on it, and a real problem at any one of them can keep it out of evidence or take it apart on cross-examination. There are two broad ways to win. We keep the result out through a motion to suppress, or we leave it in and show the jury why it does not mean what the State claims. I work both, and I start by reading the science the way the State’s own analyst does.
Each gate is a place the State can fall short, and each one is a place where the defense goes to work.
Gate One: Was the Blood Lawfully Taken
Since Birchfield v. North Dakota, 579 U.S. 438 (2016), the police generally need a warrant to draw your blood, even after a serious crash. They can skip the warrant only with free and voluntary consent or a true emergency. When the draw was unlawful, the result and the evidence that flowed from it can be suppressed.
01 No warrant and no real emergency
Under Missouri v. McNeely, 569 U.S. 141 (2013), the natural fall of alcohol in the blood is not an automatic emergency. Schmerber allowed a warrantless draw only because a crash, hospital transport, and scene investigation left no time for a warrant. Florida courts apply that case by case, as in exigent circumstances and the blood draw warrant requirement.
02 Consent that was not free
The implied consent law only applies when blood is taken on probable cause that an impaired driver caused death or serious injury. When an officer reads the implied consent warning outside that situation, the threat of a suspension makes any resulting consent involuntary, as the Florida Supreme Court held in Montes-Valeton v. State, 216 So. 3d 475 (Fla. 2017).
03 A warrant they could not get
Florida law does not authorize a blood warrant in a misdemeanor DUI. The line is drawn at felonies in State v. Geiss, 70 So. 3d 642 (Fla. 5th DCA 2011), which we cover in misdemeanor versus felony warrants.
Do not miss this
A crime lab blood result at or above 0.08, or a refusal, can trigger an administrative license suspension.
Under Florida Statute 322.2615, a qualifying blood result brings an administrative suspension on top of the criminal case. Because the result comes back from the lab later, the notice of suspension and the 10-day window to demand a formal review hearing with the DHSMV usually run from when the result is reported, not from the arrest. Acting early also lets us move to preserve the sample for an independent test.
Gate Two: Was the Sample Sound
Even a lawful draw produces a reliable number only if the blood that reached the instrument still reflected your body. A legal draw is supposed to follow FDLE Rule 11D-8.012, with a qualified drawer, a non-alcohol antiseptic, and an approved kit. From there the defense looks at the preservative and the risk of fermentation, at hemolysis and a degraded sample, at storage and the time before testing, and at the chain of custody. The way the tube is handled matters too, from tourniquet time to mixing the preservative.
Gate Three: Was the Test Done Right
Florida crime labs measure blood alcohol by headspace gas chromatography. The result depends on the calibration and the internal standard, on clean blanks and the absence of carryover, and on a stated measurement uncertainty. Behind the instrument sit the lab’s accreditation and validation records, which are discoverable and often revealing. This is the gate where the forensic credential does the most work.
A Feature of Every Blood Case: The Analyst Who Has to Face You
The lab report is a statement by a person, and that person has to testify. After Smith v. Arizona, 602 U.S. 779 (2024), the State cannot send a stand-in to read in the work of the analyst who ran your sample. We hold the State to that, which is the heart of the non-testing analyst and the Confrontation Clause.
Gate Four: Does the Number Mean What They Say
A number is only as good as its interpretation. Hospital results are usually serum, which reads higher than the whole blood the law uses. A test taken hours after driving invites retrograde extrapolation, which is unreliable. And in a drug case, the presence of a substance is not proof of impairment at the wheel.
Medical Blood Is a Different Fight
When the State uses hospital blood drawn for treatment, the rules change. That blood carries no legal presumption, and the State has to clear extra hurdles before a jury hears it. We cover the split in legal blood versus medical blood, the reliability gate of the Hunter hearing, and the medical records privilege that protects your hospital file.
Every Issue We Challenge
Do You Need an Expert?
Not in every case. As an ACS-CHAL Forensic Lawyer-Scientist with chromatography training, I read the chromatograms, the calibration data, and the quality-control records myself, and I bring in an independent toxicologist when a case calls for one. Your right to an independent retest of the same sample can also be decisive. See what the Lawyer-Scientist training covers.
I started out as an Assistant Public Defender in Florida’s Thirteenth Judicial Circuit, in Tampa, and today I am one of six ACS-CHAL Forensic Lawyer-Scientists in Florida. I work both the science and the procedure in your case the way the State’s own analysts and officers are trained to, and I show a jury the exact point where the evidence does not hold up. Learn more about my background.
Questions We Hear About Fighting a Blood Test
Can a blood test be thrown out?
Yes. If the draw was unlawful, with no warrant, no valid consent, and no true emergency, a motion to suppress can keep the result and the evidence that followed out of the case. Even a lawful draw can be undercut when the sample was mishandled or the testing was flawed. The first step is reading the crime lab file and the data.
Is it better to keep the test out or attack it at trial?
It depends on the facts, and often we do both. Winning a motion to suppress can remove the blood result entirely. When the result stays in, we show the jury why the science does not support it. We pursue the strongest path the case allows rather than committing to one approach too early.
The police forced my blood after a crash. Was that legal?
Maybe not. Florida Statute 316.1933 lets an officer require a blood draw, with reasonable force, when there is probable cause that an impaired driver caused death or serious bodily injury. The Fourth Amendment still generally requires a warrant unless a true emergency or valid consent applies. We test whether the probable cause and the warrant exception truly existed.
Do I need an expert to fight a blood test?
Not always. A forensic lawyer-scientist can read the chromatography and the lab records directly and find the problems, then retain an independent toxicologist when the case warrants it. Your right to an independent retest of the sample can also carry significant weight.
Start with the DUI blood test overview, or see breath test defense and the main St. Petersburg DUI defense page.
This page is general information, not legal advice, and it does not create an attorney-client relationship. Blood testing in Florida is governed by Fla. Stat. 316.1932, 316.1933, and 322.2615 and the Florida Administrative Code chapter 11D-8. Procedures and rules change, and every case turns on its own facts. Past results do not guarantee a similar outcome.
