Blood draws are becoming increasingly common in Tennessee DUI investigations. As law enforcement agencies across the state seek more accurate and reliable evidence, blood testing is often preferred over traditional breath tests—especially in cases involving suspected drug impairment or serious accidents. But this growing trend raises important legal questions: Can police draw your blood without your consent? Do they need a warrant? And what are your rights if you refuse?
Tennessee DUI laws give officers certain powers under what’s known as the implied consent law, but those powers have limits. Understanding when a blood draw is legal—and when it crosses the line—can have a major impact on your case.
In this blog, we’ll explore why blood draws are on the rise, what Tennessee law says about them, and what you can do if you’re facing DUI charges involving a blood test.
When Can Police Draw Blood Without Consent?
With the rise in DUI blood testing across Tennessee, many people are surprised to learn that refusing a blood test doesn’t always prevent law enforcement from getting a sample. But under both federal and Tennessee law, officers can only draw blood without your consent in specific, legally justified situations.
In most cases, police must obtain a search warrant before drawing your blood without your permission. A blood draw is considered a search under the Fourth Amendment, and courts have made it clear that it’s a highly invasive one. To be legal, the officer must show probable cause that you were driving under the influence, and a judge must approve the warrant. Many departments now use electronic warrant systems, which means an officer can get approval within minutes—even late at night or from the roadside.
However, there are limited exceptions to the warrant requirement. Tennessee law and court decisions recognize a few situations where a warrant might not be required:
- Exigent Circumstances: If there’s a genuine emergency—such as a crash with serious injuries—and there’s no time to get a warrant, police may argue that they had to act quickly to prevent the loss of evidence. However, courts are strict about this. The natural breakdown of alcohol in your system is not enough on its own to justify a warrantless blood draw.
- Unconscious or Incapacitated Driver: If you’re unconscious or physically unable to refuse, Tennessee’s implied consent law may allow officers to seek a blood draw. Whether a warrant is still required depends on the specific circumstances, including the availability of a judge and the presence of true exigent circumstances.
- Mandatory Testing in Serious Accidents: In cases involving serious injury or death, Tennessee law gives officers the authority to require a blood test, though whether that can be done without a warrant depends on the specific facts and case law.
While courts allow blood draws in certain warrantless scenarios, forcible blood draws are legally risky for police investigations. If officers violate your constitutional rights during the process, your defense attorney may be able to get the blood test results suppressed, which can severely weaken the prosecution’s case.
When Is Consent to a Blood Draw Truly Voluntary?
Police may obtain a blood sample in one of two ways: through voluntary consent, or through implied consent under Tennessee law. However, not all consent is legally valid. For consent to justify a warrantless blood draw, it must be knowing, voluntary, and not the result of coercion or incapacity. This is a critical issue in many Tennessee DUI cases.
Voluntary Consent vs. Implied Consent
A driver can expressly agree to a blood draw—this is considered voluntary consent. Separately, Tennessee’s implied consent law treats drivers as having already agreed to chemical testing as a condition of driving. But implied consent does not automatically mean police can forcibly draw blood, and it does not override constitutional protections. In both situations, the key legal question becomes whether the driver was capable of giving valid consent at the time.
When Consent May Not Be Voluntary
Defense attorneys frequently challenge blood draws by arguing that consent was not voluntary due to the driver’s physical or mental condition, including:
- Medication or medical treatment
A driver who has been given prescription drugs, pain medication, sedatives, or IV fluids—especially after a crash—may lack the mental clarity required to give valid consent. - Head trauma or concussion
Head injuries can significantly impair judgment, awareness, and comprehension. Even if a driver appears responsive, head trauma may render any consent legally unreliable. - Severe intoxication or impairment
While impairment alone doesn’t automatically invalidate consent, extreme intoxication—especially combined with other medical factors—can support an argument that consent was not knowing or voluntary. - Hospital or emergency-room settings
Blood draws taken while a driver is injured, disoriented, or undergoing treatment are frequently challenged, particularly when officers rely on alleged “consent” rather than a warrant.
If consent is ruled involuntary, the blood draw may be deemed unconstitutional, and the results could be suppressed. This is one of the most powerful defenses in DUI cases involving hospital blood draws.
Tennessee’s Implied Consent Law (Including 2026 Changes)
Even when Tennessee’s implied consent law applies, law enforcement must still comply with constitutional requirements when obtaining a blood sample. That means officers generally need a valid search warrant—unless a legal exception applies.
Under T.C.A. § 55-10-406, anyone who operates a motor vehicle on Tennessee roads is considered to have already consented to chemical testing—such as blood, breath, or urine—if an officer has reasonable grounds to believe the driver is under the influence. This is known as implied consent.
In practice, this allows police to request a chemical test after a lawful DUI arrest. However, you still have the right to refuse—though refusal carries consequences, even if your blood is later drawn by other legal means.
Key Changes in 2026
Updates to Tennessee’s implied consent laws in 2026 now make it clear that refusal triggers consequences, regardless of whether your blood is later drawn by warrant or not. Previously, defense attorneys could argue that obtaining a sample later negated the refusal. That argument no longer holds.
The law also reflects the growing role of blood testing in DUI cases, especially those involving suspected drug use. Blood tests are now widely used due to their accuracy and ability to detect substances that breath tests cannot.
Finally, the law emphasizes that it’s the act of refusal itself—not whether the refusal affected the investigation—that leads to penalties. Simply saying “no” to a lawful request for testing is enough.
What Has Not Changed
Implied consent does not give police automatic authority to forcibly take your blood. If you refuse, officers still need to rely on:
- A search warrant, or
- A valid legal exception (like unconsciousness or true exigent circumstances)
These protections are grounded in both the U.S. Constitution and Tennessee law, and they remain a crucial part of defending against DUI charges.
How Barnes & Fersten Can Help in DUI Blood Draw Cases
At Barnes & Fersten, we understand how overwhelming a DUI arrest can be—especially when it involves a blood draw without your consent. Our Knoxville-based defense team has extensive experience challenging unlawful blood tests and protecting the rights of drivers across East Tennessee. Here’s how we help:
1. We Challenge the Legality of the Blood Draw
Our first step is to examine whether law enforcement followed proper legal procedures when obtaining your blood. We dig into questions like:
- Did the officer have probable cause for the DUI arrest?
- Was a search warrant obtained—or was one required?
- Did you give clear and voluntary consent?
- Were any claimed exceptions to the warrant requirement justified?
If your rights were violated, our DUI attorneys will file a motion to suppress the evidence. If successful, this can prevent prosecutors from using the blood test in court, dramatically weakening their case.
2. We Fight to Protect Your License
Refusing a chemical test—even if blood is later drawn—can lead to an automatic license revocation under Tennessee’s implied consent law. We act quickly to request and represent you at your administrative license hearing, where we challenge the suspension and present evidence that may help preserve your ability to drive.
3. We Build a Strategic Defense from the Ground Up
A DUI case is about more than just the blood test. We evaluate every stage of your arrest, including:
- The legality of the initial traffic stop
- Officer behavior and field sobriety testing
- The chain of custody and handling of your blood sample
- Whether any medical conditions may have affected your ability to consent
When blood evidence is excluded, prosecutors may be forced to offer a lesser charge or dismiss the case entirely. Our goal is to uncover every flaw and use it to your advantage.
4. We Act Quickly to Protect Your Rights
In DUI cases, timing matters. Waiting too long can mean lost evidence, missed filing deadlines, or overlooked legal arguments. The sooner you contact our office, the more we can do to preserve your record, protect your license, and fight for the best possible outcome.
Don’t Face a DUI Charge Alone - Call Barnes & Fersten
Being charged with DUI in Tennessee can turn your life upside down. You may be facing license suspension, court dates, fines, or even jail time—and the legal system doesn’t wait for you to catch up.
At Barnes & Fersten, we’ve helped hundreds of people across East Tennessee protect their rights, challenge the evidence against them, and move forward with confidence. We know the law, we know the courts, and we know how to build a strong defense that puts you in the best position possible.
Don’t try to navigate this alone or wait until it’s too late to act. Call Barnes & Fersten at 865-805-5703 or fill out our contact form for a free consultation, and find out how we can help you take control of your case and protect your future.
Attorney At Law, Managing Partner
Brandon D. Fersten is an esteemed Knoxville attorney practicing DUI, criminal defense, and juvenile law. Known for his empathetic approach and commitment to his clients, he brings a record of favorable case outcomes including dismissals and not guilty verdicts at jury trials resulting in Brandon being recognized as one of the “Top 40 Under 40” in Criminal Defense, U.S. News’ Best Lawyers: “Ones to Watch,” and Super Lawyers’ “Rising Stars”. Brandon’s professional accolades, combined with his passion for justice, position him as a reliable criminal defense advocate in the East Tennessee legal landscape, including Knox County, Blount County, Sevier County, Loudon County, Roane County, Anderson County, Cumberland County, Hamblen County, Monroe County, and McMinn County.
