When a driver is arrested for DUI in Tennessee, the officer’s decision to request a blood draw sets off a series of legal requirements that must be followed precisely. Blood evidence is the centerpiece of most DUI prosecutions, and the procedures the State must follow to obtain and process that blood sample are governed by statute, case law, and constitutional protections. If any step in the process fails, the blood evidence may be subject to suppression — meaning the jury may never see it.
This guide covers the legal framework for DUI blood draws in Tennessee: when police can draw blood, what the warrant requirement means after the U.S. Supreme Court’s decision in Missouri v. McNeely, who can lawfully draw blood, how chain of custody works, what independent testing rights a defendant has, and how a defense lawyer challenges blood draw evidence in court.
Tennessee’s Implied Consent Law
Tennessee’s implied consent statute, T.C.A. § 55-10-406, provides that any person who operates a motor vehicle in Tennessee is deemed to have given consent to a test or tests for the purpose of determining the alcohol or drug content of that person’s blood. This is called implied consent because the consent is automatic by virtue of driving on Tennessee roads — no one signs a form agreeing to it. The consent exists as a legal fiction that the legislature created to facilitate DUI enforcement.
Under implied consent, when an officer has reasonable grounds to believe a person has been driving under the influence, the officer may request that the person submit to a blood, breath, or urine test. The driver has the right to refuse the test, but refusal carries its own consequences: an automatic one-year license revocation under Tennessee’s implied consent revocation statute, independent of and in addition to any penalties for the DUI itself.
Implied consent does not mean the officer can forcibly draw blood without limitation. The U.S. Supreme Court’s 2013 decision in Missouri v. McNeely fundamentally changed how Tennessee officers must approach blood draws, and understanding that case is essential to understanding the current state of the law.
Missouri v. McNeely and the Warrant Requirement
In Missouri v. McNeely, 569 U.S. 141 (2013), the U.S. Supreme Court held that the natural dissipation of alcohol in the bloodstream does not, standing alone, constitute a per se exigent circumstance that justifies a warrantless blood draw in every DUI case. Before McNeely, many law enforcement agencies operated under the assumption that because alcohol dissipates over time, there was always an exigency that justified drawing blood without a warrant. The Supreme Court rejected that position.
The Court held that the Fourth Amendment requires that, in the absence of a warrant, officers must demonstrate exigent circumstances on a case-by-case basis before conducting a blood draw. The mere fact that alcohol dissipates is not enough. The officer must show that obtaining a warrant would have been impractical under the specific circumstances of the case — for example, that the delay caused by obtaining a warrant would have resulted in a significant destruction of evidence beyond the normal rate of alcohol metabolism.
After McNeely, the standard practice in Tennessee DUI cases involving blood draws is for officers to obtain a search warrant before drawing blood. Most jurisdictions in Middle Tennessee have streamlined the warrant process, allowing officers to apply for telephonic warrants or electronic warrants that can be obtained relatively quickly. But the warrant requirement exists, and a blood draw conducted without a valid warrant and without a recognized exception to the warrant requirement is subject to challenge through a suppression motion.
Exceptions to the Warrant Requirement
While the warrant requirement is the default after McNeely, there are recognized exceptions under which a blood draw may be conducted without a warrant:
Actual Consent
If the driver voluntarily consents to the blood draw after being properly advised of their rights, the blood draw is lawful without a warrant. Actual consent must be voluntary and not the product of coercion. The fact that the driver initially agreed to the blood draw is not the end of the analysis — the defense can argue that the consent was not voluntary based on the circumstances, including whether the driver was informed of the right to refuse, whether the officer’s conduct was coercive, and whether the driver was in a condition to give meaningful consent.
True Exigent Circumstances
The McNeely Court did not say that exigent circumstances can never justify a warrantless blood draw — it said that the natural dissipation of alcohol alone is not enough. Exigent circumstances may exist where the officer can demonstrate specific facts showing that the delay required to obtain a warrant would result in a significant loss of evidence. For example, if the driver was taken to the hospital after a serious accident and hours passed while the driver received medical treatment, the additional delay of a warrant application might justify a warrantless draw under those specific facts.
Mandatory Blood Draw Situations
Tennessee law provides for mandatory blood draws in certain situations, including DUI cases involving accidents resulting in death or serious bodily injury. Under these statutes, the officer may direct a blood draw regardless of the driver’s consent. Even in mandatory blood draw situations, however, the McNeely warrant requirement still applies unless an exception to the warrant requirement is present. Officers typically obtain a warrant even in mandatory blood draw cases to ensure the evidence withstands constitutional challenge.
Who Can Draw Blood Under Tennessee Law
T.C.A. § 55-10-408 governs the procedures for blood draws in DUI cases. The statute requires that blood be drawn by a physician, registered nurse, licensed practical nurse, medical technologist, medical laboratory technician, or phlebotomist. The person drawing the blood must be qualified by training and experience to perform the procedure.
A law enforcement officer cannot draw blood. This is a bright-line rule in Tennessee. If the blood was drawn by someone not qualified under the statute, the defense has a strong basis for a suppression motion. The defense may also challenge whether the person who drew the blood had the proper credentials and was acting within the scope of their licensure.
The statute also requires that the blood draw be performed in a medically acceptable manner. This means using proper sterilization procedures, drawing from an appropriate site (typically the arm), and using a non-alcohol-based antiseptic to clean the draw site. The use of an alcohol-based swab to clean the injection site before a blood draw intended to measure blood alcohol content is an obvious contamination concern and is a recognized basis for challenging blood test results.
Chain of Custody Requirements
Once blood is drawn, it must be properly preserved, labeled, stored, and transported to the testing facility. The chain of custody is the documented record of every person who handled the blood sample from the moment of the draw to the moment the test results are produced. Any break in the chain of custody — a period where the sample was unaccounted for, a failure to document a transfer, improper storage conditions — can be grounds for challenging the admissibility of the blood test results.
Tennessee courts have held that the State must establish a chain of custody sufficient to assure the identity of the evidence and its integrity. This does not require the State to account for every moment the sample was in transit, but it does require a showing that the sample was not tampered with or contaminated. Gaps in the chain of custody do not automatically render the evidence inadmissible, but they go to the weight the jury should give the evidence and may support a defense argument that the results are unreliable.
Common chain of custody issues include: failure to properly seal the blood vial, failure to refrigerate the sample during storage, excessive delay between the draw and the testing, failure to use proper preservatives in the blood collection tube, and documentation gaps between the draw site and the laboratory.
Independent Testing Rights
Under T.C.A. § 55-10-408(c), a person who is tested for DUI has the right to have an additional test performed by qualified personnel and a physician of the person’s own choosing. This independent testing right is separate from the State’s testing and is at the person’s own expense. The officer is required to inform the person of this right.
The independent testing right is a critical safeguard. If the State’s blood test shows a BAC above the legal limit, the defense can obtain an independent test of the same sample or a separately drawn sample to check the State’s results. If the independent test produces a significantly different result, that discrepancy can be powerful evidence that the State’s testing was unreliable.
Failure to inform the defendant of the independent testing right is not automatically grounds for suppression, but it can be raised as a factor in challenging the overall fairness of the testing process. If the officer’s failure to advise of the independent testing right resulted in the defendant losing the opportunity to obtain an independent sample, the defense may argue that the due process rights of the defendant were violated.
Challenging Blood Draw Evidence in Court
Blood draw evidence can be challenged at multiple levels. The defense may file a pretrial suppression motion arguing that the blood draw itself violated the defendant’s Fourth Amendment rights — for example, because the warrant was defective, the blood was drawn without a warrant and without valid consent or exigent circumstances, or the officer lacked probable cause for the DUI arrest in the first place. If the suppression motion succeeds, the blood evidence is excluded from trial, and the State’s case often collapses. For more on how suppression motions work, see our guide on suppression motions in Tennessee.
Even if the blood draw survives the suppression motion, the defense can challenge the reliability of the test results at trial. This includes challenging the qualifications of the person who drew the blood, the procedures used in the draw, the chain of custody, the calibration and maintenance of the testing equipment, the methodology used by the lab, and the qualifications of the lab technician who performed the analysis. Each of these is a potential point of failure that can create reasonable doubt about the accuracy of the BAC result.
Expert witnesses play an important role in blood draw challenges. A qualified toxicologist or forensic scientist can review the State’s testing procedures and identify errors or deviations from accepted protocols. The defense may also retain an expert to explain to the jury how errors in the draw, storage, or testing process can produce inaccurate BAC results.
Another avenue of challenge is the timing of the blood draw relative to the time of driving. Blood alcohol content changes over time as the body absorbs and eliminates alcohol. If there was a significant delay between the time of driving and the time of the blood draw, the defense can argue that the BAC at the time of the draw does not reflect the BAC at the time of driving. This is called retrograde extrapolation, and it is a complex scientific issue that often requires expert testimony.
Implied Consent vs. Actual Consent: A Critical Distinction
Tennessee’s implied consent statute creates a legal obligation to submit to testing, but it does not eliminate the Fourth Amendment’s warrant requirement. The U.S. Supreme Court in Birchfield v. North Dakota, 579 U.S. 438 (2016), drew a line between breath tests and blood tests: the Court held that a breath test may be conducted as a search incident to arrest without a warrant, but a blood test — because it is more intrusive — requires either a warrant, valid consent, or an applicable exception to the warrant requirement.
This distinction matters in Tennessee practice. An officer who requests a blood draw under the implied consent statute must still either obtain a warrant or secure the driver’s actual, voluntary consent. The implied consent statute alone does not authorize a warrantless blood draw. If the driver refuses the blood draw, the officer must obtain a warrant before proceeding with the draw (or demonstrate exigent circumstances). The driver’s refusal triggers the administrative consequences of the implied consent statute — the one-year license revocation — but does not give the officer the right to draw blood by force without a warrant.
Understanding this distinction is critical for anyone facing a DUI blood draw case. The fact that an officer told the driver that Tennessee law requires consent does not make the resulting blood draw constitutionally valid. The analysis always comes back to whether the blood draw was supported by a warrant, by voluntary actual consent, or by a recognized exception to the warrant requirement.
What Happens to Your License After a DUI Blood Draw
The consequences for a driver’s license depend on whether the driver consented to or refused the blood draw. If the driver consented and the BAC result was 0.08 or above, the officer will confiscate the driver’s license and issue a temporary driving permit. The driver then has 10 days to request a hearing to challenge the license revocation.
If the driver refused the blood draw, the officer will confiscate the license and issue a notice of revocation under the implied consent statute. The refusal triggers a one-year license revocation, which is longer than the revocation for a first-offense DUI conviction (one year vs. one year, but the revocation is automatic and does not require a conviction). The driver has the right to request a hearing to challenge the implied consent revocation, but the grounds for challenge are limited.
DUI cases involving blood draws often have parallel tracks: the criminal prosecution for DUI and the administrative license revocation proceeding. These are separate proceedings with different burdens of proof, different timelines, and different consequences. Both must be addressed. For an overview of how DUI proceedings work in the broader context of bond hearings and pretrial procedure, see our related guide.
Frequently Asked Questions
Can police draw my blood without a warrant in Tennessee?
In most circumstances, no. After the U.S. Supreme Court’s decision in Missouri v. McNeely (2013), a DUI blood draw in Tennessee generally requires either a search warrant, the driver’s voluntary actual consent, or a showing of exigent circumstances beyond the mere natural dissipation of alcohol. Most officers in Davidson County and throughout Middle Tennessee now obtain warrants before conducting blood draws. A blood draw conducted without a valid warrant and without a recognized exception to the warrant requirement is subject to a suppression motion.
What happens if I refuse a blood draw in Tennessee?
Refusing a blood draw triggers an automatic one-year license revocation under Tennessee’s implied consent statute, T.C.A. § 55-10-406. The officer may also seek a search warrant and conduct the blood draw over your refusal. Your refusal may be admitted as evidence at trial, although its admissibility and the weight the jury gives it are subject to legal argument. The refusal does not prevent the State from obtaining blood evidence if the officer obtains a warrant.
Who is allowed to draw blood in a Tennessee DUI case?
Under T.C.A. § 55-10-408, blood in a DUI case must be drawn by a physician, registered nurse, licensed practical nurse, medical technologist, medical laboratory technician, or phlebotomist. A law enforcement officer cannot draw blood. The person drawing the blood must be qualified by training and experience, and the draw must be conducted in a medically acceptable manner. If blood was drawn by an unqualified individual, the defense has grounds to seek suppression.
Can I get an independent blood test after a DUI arrest?
Yes. Under T.C.A. § 55-10-408(c), a person tested for DUI has the right to an additional, independent test performed by qualified personnel and a physician of the person’s own choosing, at the person’s own expense. The officer is required to inform you of this right. An independent test that produces a significantly different result from the State’s test can be powerful evidence in your defense.
How long does the State have to test the blood sample?
Tennessee does not set a specific statutory deadline for testing the blood sample, but excessive delay between the blood draw and the testing can be a basis for challenging the results. Blood samples must be properly preserved with appropriate anticoagulants and refrigerated. Failure to do so can cause fermentation of the sample, which produces alcohol and artificially inflates the BAC result. If there is evidence that the sample was not properly stored or was subject to excessive delay, the defense can challenge the reliability of the test results.
Talk to a Criminal Defense Lawyer
Nathan Cate handles DUI cases involving blood draw evidence in Davidson County and throughout Middle Tennessee. Blood draw challenges require close attention to constitutional requirements, statutory procedures, and forensic science. If you have been charged with a DUI based on a blood test, the procedures used to obtain and process that blood sample may be subject to challenge.
(615) 664-8083
222 2nd Avenue North, Suite 220, Nashville, TN 37201