No, you should not plead guilty simply because your BAC is above a .08% BAC without a skilled DUI defense attorney fully evaluating your case, your circumstances, and advising you as to the potential benefits and risks of proceeding forward with your case. There are countless factors in DUI cases that can impact the accuracy and validity of the blood or breath draw, and the admissibility of the tests to be used against you in the first place.
Barnes & Fersten’s DUI defense team have gotten hundreds of DUI cases reduced or dismissed despite a blood level above a .08% BAC. Of course, every case is different, and we cannot guarantee results, but that is why you must have a DUI defense attorney evaluate the chances of avoiding a lifelong DUI conviction.
Most people think of a DUI charge as something that happens only when a driver is obviously drunk or high. Slurred speech, swerving on the road, failing a field sobriety test—these are the images that often come to mind. But under Tennessee law, you can be charged and convicted of DUI even if you don’t appear impaired at all.
This is because Tennessee has what’s known as a “DUI per se” law. In a DUI per se case, the key factor isn’t whether you were driving erratically or seemed intoxicated—it’s whether your blood alcohol concentration (BAC) was at or above the legal limit. Simply put, the BAC number alone can be enough for a conviction, even if you felt completely fine behind the wheel and performed well on field sobriety tests. Your attorney can argue that a lack of indicators of impairment prove doubt as to the blood results reliability, but you can be convicted basd on the number alone.
In this article, we’ll break down what DUI per se means in Tennessee, how it differs from impairment-based DUI, how BAC is measured, and how knowing your rights can change the outcome if you’re accused in East Tennessee.
DUI Per Se In Tennessee Defined
Under Tennessee law, DUI per se is spelled out in Tennessee Code Annotated § 55-10-401(a)(2). It makes it illegal to operate or be in physical control of a motor vehicle with a blood alcohol concentration at or above the legal limit, regardless of whether you appear impaired.
The legal BAC limits in Tennessee are:
- 0.08% for most drivers age 21 and over
- 0.04% for CDL holders in commercial vehicles
- 0.02% for drivers under 21 (zero-tolerance standard)
Here’s what makes DUI per se different: once your BAC is over the legal threshold, the State doesn’t have to prove you were driving poorly, failed a sobriety test, or even “looked drunk.” The BAC number itself is enough to meet the legal standard for a DUI conviction.
Rights Reminder 🔎
If you’re over the legal limit, the prosecution already has what they need for a DUI per se charge. Any extra information—such as admitting to drinking, explaining how much you had, or trying to “pass” roadside tests—just gives law enforcement more evidence to use against you.
Remember: you have the right to remain silent, and you are not required to answer questions about your alcohol consumption.
How DUI Per Se Differs From Impairment-Based DUI
Tennessee law recognizes two main ways a driver can be charged with DUI:
Type of DUI
What the State Must Prove
Common Evidence Used
Example Scenario
DUI per se
That your BAC was at or above the legal limit (0.08%, 0.04%, or 0.02%, depending on the driver)
Breath or blood test results showing BAC over the limit
You feel completely fine, but a breath test shows 0.08% BAC → guilty of DUI per se, even without other signs of impairment. Minimum jail sentence also increases to 7 days from 48 hours on a 0.15% BAC
Impairment DUI
That you were under the influence to the point that it affected your ability to safely operate a vehicle
Officer observations (slurred speech, unsteady balance), field sobriety test results, driving behavior
You blow a 0.05% BAC, but fail multiple field sobriety tests and were weaving in traffic → possible impairment DUI charge
Key Takeaways
- DUI per se: The BAC number alone is enough to convict—no need for proof of bad driving or other impairment indicators.
- Impairment DUI: BAC can be below the legal limit, but other evidence suggests unsafe driving due to drugs, alcohol, or both.
Rights Reminder 🔎
Field sobriety tests in Tennessee are voluntary—and often highly subjective. Officers may use any “clues” from these tests to claim you were impaired, even if your BAC was borderline or below the limit. If you’re already over the legal BAC, performing field tests won’t help you—it will only give the State more evidence to work with.
How BAC Is Measured
When Tennessee officers investigate a DUI, they’re looking for one crucial piece of evidence: your blood alcohol concentration. Here’s how that number is created and what you should keep in mind:
1) Roadside: Observation → (Sometimes) a Portable Breath Test
- After the stop, the officer notes driving behavior, odor of alcohol, speech, and coordination.
- Some departments use a portable breath test (PBT) at the roadside to estimate alcohol presence. These handheld devices are screening tools and are more error-prone than the machines used at the station. Temperature swings, mouth alcohol content, and poor calibration can all skew results.
Why this matters: Anything you say (“I had two beers”) plus a PBT reading can help justify an arrest—even if the test isn’t reliable. Remember: you don’t have to discuss alcohol consumption with the police.
🔍 Are Portable Breath Tests Legal: PBT device results are inadmissible in court and cannot be used against you to determine the blood alcohol content of an individual due to reliability issues. However, they are legal and sometimes relied upon by officers for probable cause.
2) After Arrest: The “Evidentiary” Test
Once you’re arrested, officers typically request an evidentiary breath test (commonly on an Intoximeter EC/IR II) or a blood draw.
- Breath Test (EC/IR II): Measures alcohol in deep lung air to estimate BAC. Proper protocol requires a continuous observation period of 20 minutes with no burping, regurgitation, eating, or drinking. The machine must be maintained and calibrated, and the operator must follow the checklist precisely.
- Blood Test: Collected by trained personnel and analyzed in a lab. Accuracy hinges on sterile technique, correct preservatives inverted properly in the tube, accurate labeling, proper storage temperature, and an unbroken chain of custody from collection to analysis.
Why this matters: Small deviations—skipping the observation period, expired mouthpieces, mislabeled vials, warm storage, or gaps in custody—can inflate results or make them unreliable in court. It can result in fermentation, and other issues essentially resulting in the tested level being inflated from the time the blood was taken.
Implied Consent In Tennessee - Should You Refuse Tests?
Tennessee has an implied consent law (T.C.A. § 55-10-406), meaning that by driving on Tennessee roads, you are deemed to have consented to BAC testing if lawfully arrested for DUI. If a court finds an implied consent violation, your license can be revoked: typically 1 year for a first offense, 2 years with certain priors or a crash causing injury, and up to 5 years if a fatality is involved. In many cases, a restricted license with ignition interlock may be available.
As of January 1, 2026 the law will be amended to result in an eighteen (18) month loss of license. As of May 2025, an individual can lose their license from an implied consent regardless of whether the State received a search warrant for blood.
Why We Recommend Refusing Fields And Chemical Tests
A clean chemical number is the State’s strongest evidence in a DUI per se case. Refusing often denies prosecutors that linchpin and keeps key defenses alive (the stop, the advisement, the warrant, chain of custody). It is important to note that despite common belief, a refusal does not meanautomatic suspension of your license while your case is pending—you can fight the implied consent allegation in court.
Rights Reminder 🔎
While implied consent means refusing a test can carry penalties, you still have the right to ask if you are under arrest, request to speak to an attorney, and avoid volunteering extra information. If your BAC is over the limit, the number alone is enough for a DUI per se charge—agreeing to roadside breath tests or field sobriety tests before arrest often just hands the officer more evidence to use against you later. If convicted of DUI you will lose your license for a year anyway, but the additional six (6) months as of January 1, 2026, results in the implied consent civil violation being additional punishment.
We expect that the new law will be challenged on constitutional grounds considering Tennessee courts have previously held that the implied consent violation is civil in nature but the additional punishment creates a potential constitutional issue to be addressed by the courts.
Defenses To DUI Per Se In Tennessee
Even if your BAC was above the legal limit, that doesn’t mean the State’s case is unshakable. DUI per se charges can be challenged in several ways, and an experienced defense attorney will know how to spot weaknesses in the prosecution’s evidence.
Challenging the Traffic Stop
A DUI case can fall apart if the traffic stop never should have happened—or if a routine stop was stretched into a fishing expedition without new facts. Officers need reasonable suspicion to pull you over, and they can’t extend the stop beyond its basic mission (license, registration, insurance) unless they develop more cause. Long delays before DUI questions, repeated “just one more thing” requests, and consent searches without fresh suspicion are red flags. If the stop or prolongation is unlawful, the BAC result and other evidence can be suppressed.
Our attorneys routinely argue that officers lacked reasonable suspicion or specific reasons to conclude an individual is under the influence, rather than simply consumed alcohol, to prolong the stop into a DUI investigation by conducting field sobriety tests.
Questioning the Breathalyzer’s Accuracy
A breath number doesn’t come into evidence automatically. Tennessee courts look for a proper foundation: trained operator, certified instrument, correct procedure, and a continuous observation period (often 20 minutes) to guard against mouth alcohol. If the officer was multitasking, turned away, or left the room, the observation requirement can be challenged to suppress the breathalyzer results (SENSING). Chewing tobacco, mints, mouthwash, burping, or reflux during that period can also inflate readings.
Issues with Blood Tests
Blood testing is powerful evidence—but only if it’s lawfully obtained and properly handled. Generally, officers need a valid warrant or truly voluntary consent, and the collection must follow medical/legal standards. Defects include bad warrant language, implied “consent” after threats, use of alcohol swabs, wrong tubes, poor mixing, temperature swings, or broken seals. Any one of these can undermine or exclude the BAC.
Voluntary consent can be challenged if it was not intelligently and knowingly given. For example, serious injuries such as head trauma or medications provided by EMS can cause blood results to be inadmissible.
Storage of the blood samples in inappropriate temperature conditions can cause the blood results to be unreliable. When blood samples are delivered from East Tennessee to Nashville for blood testing, they should be on ice to ensure proper storage.
Tubes that are not properly mixed through inversions of the blood tubes can result in an unreliable blood result. This is because the sodium fluoride and potassium oxulate that are in the tubes prior to the blood draw must be mixed to properly preserve the blood and prevent blood clotting.
No Probable Cause to Arrest
Even before any test, officers must have probable cause based on the totality of the circumstances. Thin driving cues, normal speech and demeanor on video, medical issues, uneven surfaces, bad weather, or poorly instructed SFSTs weaken the arrest. If probable cause is lacking, the arrest—and the subsequent test—can be suppressed. This defense is especially effective when the video doesn’t match the report.
Lack of probable cause is the most common DUI defense to high blood results. Should probable cause be found, the same argument can be made to allege that there must have been an issue with the blood draw, even if the defense cannot prove it, because there is a clear disconnect between the blood results and the defendant’s actions.
Rights Reminder 🔎
The burden of proof is on the State. Every statement you make, every roadside test you agree to, and every explanation you offer can help prosecutors build their case. In a DUI per se situation, where the BAC reading is already the main evidence, your defense often begins by saying less and calling a DUI lawyer immediately.
Get A Proven DUI Defense Attorney For Your Case
Being charged with DUI per se in Tennessee doesn’t mean your case is decided. The stop, the science, and the procedures can all be challenged in court with the right DUI defense team on your side.
At Barnes and Fersten, our attorneys focus exclusively on DUI and criminal defense in East Tennessee. We know how to challenge DUI per se cases, from questioning the validity of BAC tests to exposing weaknesses in the prosecution’s evidence. Call our law firm today at 865-234-3409 or fill out our contact form for a free consultation. The sooner you call, the sooner we can begin building a personalized defense for your case.
