In Tennessee, the difference between a routine DUI and a life-changing felony can come down to just a few decimal points. With recent changes in state law, a blood or breath test reading of 0.15% BAC or higher now carries far more serious legal consequences than ever before. What once might have meant a misdemeanor DUI could now escalate to a felony charge with years of prison time, higher fines, and a permanent criminal record.
This article explains what changed in Tennessee DUI law, why the 0.15% threshold matters so much, and what you should know if you or someone you care about faces a high BAC result.
The Tiny Difference That Makes a Huge Impact
Imagine two Tennessee drivers pulled over on the same night. One blows 0.14%, the other 0.15%. At first glance, that may seem like a rounding error but legally, it’s a world apart. Since mid-2025, the aggravated DUI threshold in Tennessee dropped from 0.20% to 0.15%.
That change means a driver barely above the line could now face felony-level penalties, especially if the DUI involves an accident, prior convictions, or injuries. Even without prior offenses, the new limit opens the door to enhanced sentencing and stricter penalties.
What the New Tennessee DUI Law Says
- Aggravated DUI charges may apply if your BAC is 0.15% or higher, and the case involves a crash, injuries, or previous DUI convictions.
- Vehicular assault or homicide can be charged at the same 0.15% BAC level if serious harm or death occurs.
- Enhanced penalties may include longer jail time, multi-year license suspensions, ignition interlock requirements, and steep fines.
In short: a few tenths of a percentage can now be the difference between a misdemeanor and a felony conviction.
Understanding How BAC Is Measured
Tennessee law enforcement uses three main methods to determine blood alcohol concentration (BAC):
- Breath tests – quick and common, but dependent on proper calibration.
- Blood tests – considered more accurate but subject to handling errors.
- Oral fluid (saliva) tests – newly authorized in 2025, still under review for reliability.
Even small variations can occur based on food intake, metabolism, or medical conditions like acid reflux or diabetes. That’s why skilled DUI defense attorneys often challenge how the test was conducted, whether the equipment was maintained properly, and whether the results were interpreted correctly.
Why Tennessee Lowered the Limit
Lawmakers argued that the risk of fatal crashes rises sharply once a driver exceeds 0.15% BAC. Lowering the threshold was intended to align Tennessee with national standards and increase deterrence for high-BAC driving.
While the law aims to promote safety, it also means that many more drivers could now face aggravated DUI or felony-level charges for relatively minor differences in alcohol levels.
Real-World Example: A Fraction That Changes a Life
Consider two nearly identical DUI arrests in Nashville:
- Driver A: BAC of 0.14% → charged with standard misdemeanor DUI.
- Driver B: BAC of 0.153%, with one prior DUI → charged with aggravated vehicular assault, a felony carrying mandatory prison time.
That tiny difference of 0.013% BAC transformed the second driver’s entire legal future from potential probation to years behind bars.
What’s at Stake
A BAC over 0.15% can trigger serious penalties, including:
- Felony classification and a permanent criminal record
- Mandatory prison sentences (no early release for years)
- Lengthy license suspensions
- Hefty fines and restitution if injuries occurred
- Skyrocketing insurance rates
- Employment and reputation loss
For many Tennesseans, these consequences ripple through every part of life—from family to finances to future job prospects.
Your Rights and Smart Next Steps
If you’ve been charged with DUI in Tennessee, here’s what to remember:
- Do not panic or assume guilt. BAC tests can be challenged.
- Contact a qualified DUI attorney immediately. The sooner a lawyer reviews your case, the better your chances of finding errors in testing or procedure.
- Do not post or discuss your case online. Anything you share could be used against you.
- Follow all court and interlock device requirements carefully. Even one mistake can reset your compliance period.
Tips to Avoid Risk Altogether
- Use a designated driver or rideshare after drinking.
- Know that “just a couple of drinks” may already push you close to 0.15% depending on your body type and timing.
- Keep track of what and when you drink, especially in social settings.
- Educate friends and family about Tennessee’s new BAC laws—prevention starts with awareness.
Quick Summary: Tennessee’s DUI Law Updates (2025)
| Change | Description |
|---|---|
| New aggravated BAC threshold | Lowered from 0.20% to 0.15% |
| New testing method | Oral fluid (saliva) test approved |
| Refusal penalties | Longer license suspensions |
| Ignition interlock rules | Stricter monitoring and compliance |
FAQ: Tennessee’s 0.15% BAC Law Explained
Q1: Is every 0.15% BAC DUI a felony?
Not necessarily. It depends on whether the case involves a crash, injuries, or prior DUI offenses.
Q2: Can BAC test results be wrong?
Yes. Breath and blood tests can be flawed due to calibration errors, medical conditions, or procedural mistakes.
Q3: What happens if I refuse a BAC test?
Refusal can lead to automatic license suspension (up to 18 months) and may be used against you in court.
Q4: Are saliva or “oral fluid” BAC tests reliable?
They’re new in 2025 and still debated. A defense attorney can challenge their validity in court.
Q5: What should I do first after a DUI arrest?
Stay calm, avoid self-incrimination, and call a DUI lawyer immediately.
Need Help?
If you’re facing DUI charges or have questions about Tennessee’s 0.15% BAC law, reach out to an experienced defense attorney. The smallest fraction can make the biggest difference—don’t leave your future to chance.