7 Myths About Breath and Blood Tests in a Tennessee DUI Case

A breath or blood test can feel like the whole case — a number that seems to decide everything before you have even called a lawyer. It is not, and much of what people believe about these tests in Tennessee is wrong. Here are seven common myths, and what the law actually says.

Myth 1: The breath machine is never wrong, so there is nothing you can do about the result.

A breath machine is not treated as infallible in Tennessee, and its result is not automatically admitted. Before a jury hears the number, the State must prove things about how the test was given — that the officer was certified, that the machine was certified, regularly checked for accuracy, and working, that you were watched for a full twenty minutes with nothing in your mouth and no drinking, smoking, or being sick, and that the procedure was followed. Tennessee courts have thrown results out, and reversed convictions, when the officer did paperwork instead of watching. What a court will not entertain is that breath testing itself is junk science — that was settled here decades ago. The result is neither perfect nor beyond challenge; the real challenge targets how the test was run.

Myth 2: The little handheld device the officer used at the roadside is the same test that will be used against you in court.

The small handheld unit an officer may offer you at the roadside is not automatically the same thing as the breath test the State uses to convict — but in Tennessee you cannot tell them apart by looking. Our state crime lab certifies both a benchtop machine and a cordless handheld one as official evidence instruments. What decides whether a reading can be used against you is not where you blew or how big the device was; it is whether that instrument is state-certified, whether the officer is currently certified on it, and whether the full procedure was followed. The roadside screening test generally only helps justify the arrest, while the number that counts comes from a certified test — and a certified handheld can produce that number even at the roadside.

Myth 3: A breath mint, mouthwash, or acid reflux will beat the breath test.

None of the three reliably beats a breath test in Tennessee. The rules were built around this concern: before the test the officer must watch you for a full twenty minutes to be sure nothing enters your mouth and you do not burp or bring anything up, the instrument is designed to catch mouth alcohol and abort, and the protocol takes two samples that must agree closely. A mint has no alcohol, so it changes the smell and nothing else. Mouthwash does contain alcohol, but by the time the real test happens you are under arrest and being watched, so the chance is gone. Tennessee courts have turned away a driver who blamed reflux and hired an expert — and used her two matching samples as proof it was not a factor.

Myth 4: You have the right to wait and talk to your lawyer before deciding whether to take the test.

There is no pause button. Once you are arrested for DUI in Tennessee, you have no right — under any constitution — to speak with a lawyer before deciding whether to take the officer's breath or blood test. The state's highest court decided that alcohol leaves the blood too quickly to build a workable rule around waiting, and refused to make an exception even when a lawyer was a phone call away. Saying "not until I talk to my attorney" does not hold the question open — the officer can write it down as your answer, and that answer counts as a refusal. A refusal costs your license in a separate case and can be described to the jury. Call a lawyer as soon as you can, but this decision is one you make alone.

Myth 5: If you refuse the breath test, the police have no way to get your blood.

Refusing the breath test does not put your blood out of reach — an officer can go to a judge, get a warrant, and have your blood drawn anyway. The warrant can be sworn and signed electronically in the middle of the night, issued by a judge anywhere in the state, and served at any hospital. Once it is presented, state law tells the medical staff not to ask you for permission again, and allows them to use reasonable force to take the sample. If no judge can be reached in time, courts have upheld draws taken with no warrant at all where the delay would have destroyed the evidence. Refusing does force the State onto the warrant track — a real argument a lawyer will look at — but it is not a wall.

Myth 6: The police cannot draw your blood unless you agree to it.

This one is false, and in a way that catches people off guard: if an officer has a warrant signed by a judge, your permission is beside the point. Tennessee law now tells the nurse or technician holding the needle not to ask you for consent, and allows them to use reasonable force to take the sample. Saying no does not stop the draw. There are also situations — a serious injury or death, a child in the car, or an unconscious driver — where testing goes forward on a warrant whether you agree or not. Your remaining protection is narrow: simply driving here does not by itself give permission, so without a warrant or emergency, the officer must rely on your actual, signed agreement. Fighting the draw can be charged as a separate crime.

Myth 7: Refusing the test costs you nothing as long as you are never convicted of DUI.

Refusing is its own matter in Tennessee, separate from the DUI charge, with its own license penalty whether or not you are ever convicted. It is written on a separate citation and decided separately; if the judge finds you refused, the license revocation is mandatory — it cannot be waived because the DUI was dropped or you were found not guilty. Tennessee's highest court upheld exactly that: a driver acquitted of DUI still lost his license for refusing. There is only one narrow escape, and it is not an acquittal — it applies when the charge is dismissed because the officer had no adequate reason to stop you, and even then restoration is discretionary. Do not assume the refusal disappears with the criminal case — it is a separate fight worth taking to a lawyer.

About the Author

David G. Ridings is a Nashville criminal defense attorney, former police officer, and former prosecutor with nearly 40 years of experience in the Tennessee justice system. Known as “DrJudge,” he educates hundreds of thousands about their rights during police encounters.

Call to Action

If you have taken — or refused — a breath or blood test in Tennessee, the smartest next step is to talk to a lawyer before you talk to anyone else. Don't talk your way into a worse position with the police; let someone who knows how these tests are challenged review exactly what happened on your night. Call David Ridings, "DrJudge," at 1-888-DRJUDGE for a conversation about your case and your options.

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