Getting pulled over can be nerve-wracking, even if you’ve done nothing wrong. But in Tennessee, that nervous behavior might be exactly what an officer uses to escalate a routine traffic stop into a full-blown DUI or drug investigation.
Can your fidgeting, shaky hands, or awkward answers really justify a search of your car? What about the smell of marijuana or hemp? The law draws a fine line between valid suspicion and unconstitutional overreach, and that line is often tested right on the roadside.
In this post, we’ll break down when police can lawfully advance a stop based on behavior, what courts in Tennessee have said about those situations, and how drivers can protect their rights during roadside encounters.
What Officers Can and Can’t Do During a Stop
When police pull you over for a traffic violation—like speeding, a broken taillight, or not wearing a seatbelt—the stop is legally limited in both scope and duration. In other words, officers are only supposed to do what’s necessary to address the reason for the stop: check your license, registration, insurance, and issue a citation or warning.
But what if the officer starts asking unrelated questions? Or calls in a K-9 unit to sniff your car? That’s where constitutional protections come in.
“Mission of the Stop” — Defined by Rodriguez v. United States
In the landmark 2015 decision Rodriguez v. United States, the U.S. Supreme Court ruled that officers cannot extend a traffic stop to investigate unrelated criminal activity unless they develop new, articulable reasonable suspicion during the encounter. Even a short delay—just a few minutes—can render a search illegal if it goes beyond the original purpose of the stop.
The reason for the delay becomes very important. Our DUI attorneys have gotten cases dismissed and reduced by arguing that an officer unlawfully prolonged the stop without just cause either waiting for another officer to arrive to conduct SFST’s for an unreasonable amount of time rather than doing it for himself or herself, or the act of even doing SFST’s was inappropriate under the circumstances.
Tennessee courts have embraced Rodriguez, applying it strictly. In State v. Graves (2023), a drug charge was thrown out after the court found that officers had unreasonably prolonged the stop while waiting for a K-9 to arrive—without having any new facts to justify the delay.
Reasonable Suspicion vs. Probable Cause
- Reasonable Suspicion is a lower standard. It means officers have specific, objective facts suggesting criminal activity may be afoot.
- Probable Cause is stronger. It means there’s enough evidence to believe a crime has been committed—justifying a search or arrest.
Understanding these standards is key to evaluating whether an officer lawfully expanded a traffic stop into a DUI or drug investigation. In Tennessee, courts look closely at the facts to ensure police didn’t act on a hunch or prolong a stop without legal cause.
Behavior That Can Trigger a DUI Investigation
Not every traffic stop starts as a DUI investigation, but certain behaviors can quickly shift the officer’s focus. In Tennessee, police are trained to look for indicators of impairment, even during a stop for something unrelated like a broken headlight or speeding. But for that shift to be lawful, they need reasonable suspicion based on specific facts—not just a vague feeling that something’s off.
Common Behavioral Red Flags for DUI:
- Odor of Alcohol or Marijuana – One of the most frequently cited reasons to begin a DUI investigation. However, odor only informs an officer that an individual consumed alcohol which is not illegal.
- Bloodshot or Glassy Eyes – Often noted in police reports, but courts look at the totality of circumstances. However, officers immediately assume alcohol in most cases disregarding the time of night, whether the individual wears contacts, or has a medical condition.
- Slurred or Slow Speech – May suggest impairment, especially if paired with other signs. Again, officers may falsely assume impairment rather than an accent or speech impediment. The officer has never met the arrestee before.
- Fumbling for Documents – Difficulty producing license and registration can raise suspicion.
- Inconsistent or Evasive Answers – May lead officers to dig deeper.
- Admission of Drinking – Even saying “just one beer” can justify field sobriety testing, but your attorney must argue against it being sufficient even with other common factors being present.
Field Sobriety Test Performance Isn’t Always Enough
Standardized Field Sobriety Tests (FSTs)—like the walk-and-turn, one-leg stand, and horizontal gaze nystagmus—are often used to build evidence of impairment. But these tests are not pass/fail in the traditional sense, and their results are subjective. Even if you appear to perform well, an officer may still claim to observe “clues” of impairment based on subtle missteps or nervous behavior.
What many drivers don’t realize is that officers may already have made up their minds before FSTs begin, based on earlier observations like the odor of alcohol, slurred speech, or admission of drinking. In Tennessee, those pre-test indicators alone may establish probable cause for a DUI arrest—regardless of your test performance.
That’s why behavior and interactions during the initial moments of a traffic stop—before you’re even asked to step out of the vehicle—can often have the biggest legal impact on your case.
Tennessee Case in Point: State v. Bell
In State v. Bell, the Tennessee Supreme Court upheld a DUI arrest even though the driver performed well on field sobriety tests. Why, you may ask? Because the officer observed several key indicators: the driver went the wrong way down a one-way street, had an odor of alcohol, and admitted he’d drank “more than I should have.” That was enough for probable cause, regardless of his test performance.
This is why hiring a DUI attorney who knows the law and handles DUI cases daily is so critical. Your attorney must articulate the lack of reasonable suspicion or probable cause through a strategically thoughtout cross-examination and argument. As the stakes get higher, getting a DUI with a child in the vehicle, a felony vehicular assault or vehicular homicide, it is imperative that your attorney knows what issues to look for and articulate it to your advantage in your defense.
Behavior That Can Trigger a Drug Investigation
While DUI suspicion often focuses on physical indicators of impairment, drug-related investigations during a traffic stop hinge more heavily on behavior, odors, and contextual clues. In Tennessee, officers must still follow the Constitution—meaning they need reasonable suspicion to turn a routine stop into a drug search. But the signs they rely on can be subjective, which makes it vital to scrutinize every step.
Common Triggers for Drug Searches:
- Unusual Nervousness – Shaking hands, trembling voice, or sweating might raise flags—but nervousness alone is not enough (see State v. Berrios below).
- Inconsistent or Conflicting Stories – Discrepancies between passengers and driver often prompt further questioning.
- Odor of Marijuana – Still a major factor, even though hemp is legal; this remains a gray area.
- Visible Contraband or Paraphernalia – Items like baggies, scales, or pipes in plain view can justify further action.
- Sudden or Suspicious Movements – Reaching under a seat or making quick moves can heighten suspicion.
- Presence in a “High-Crime Area” – Mentioned in some cases, but not sufficient by itself.
Case Spotlight: State v. Berrios
In this Tennessee Supreme Court case, officers detained a man in the back of a patrol car, questioned him at length, and searched his car—based solely on his nervous behavior. The court ruled this detention and search unconstitutional, emphasizing that nervousness, even combined with travel from a “drug source” city, did not establish reasonable suspicion.
K-9 Sniffs and Odor of Hemp
In State v. Green (2024), the Tennessee Supreme Court tackled the issue of drug-detection dogs alerting on marijuana-like smells, even though hemp is legal. The Court held that a dog’s alert is not automatically probable cause—it’s just one factor in the overall analysis. This decision reaffirmed that police need a totality of circumstances, not just an alert or smell.
What to Do During a Tennessee Traffic Stop
A traffic stop can be stressful, but understanding your rights can help you avoid making the situation worse—and may even protect your case later in court. Here’s what every driver in Tennessee should know when they’re pulled over by law enforcement:
You Have the Right to Refuse a Vehicle Search
Unless officers have a search warrant or clear probable cause (such as visible drugs or drug paraphernalia), they generally need your permission to search your vehicle. You are not legally required to consent.
You can calmly and clearly say:
“I do not consent to any searches.”
This simple statement preserves your rights and may later serve as the basis for suppressing unlawfully obtained evidence.
You Are Not Required to Answer Incriminating Questions
If an officer asks, “Have you been drinking?” or “Do you have drugs in the car?”, you are not obligated to answer. These questions are designed to gather evidence—often without advising you of your right to remain silent.
You can respond with:
“I prefer not to answer any questions without an attorney.”
This is your constitutional right under the Fifth Amendment and does not imply guilt.
You Can Ask If You Are Being Detained
If the officer appears to be prolonging the stop or asking questions unrelated to the reason you were pulled over, you have the right to ask:
“Am I free to go, or am I being detained?”
This question forces the officer to clarify whether they have legal grounds to continue holding you. If not, you may have been unlawfully detained—a fact that can be critical in court.
Always Stay Calm and Respectful
While you have rights, how you assert them matters. Avoid arguing or refusing to provide your driver’s license or registration. Comply with basic legal requirements, but assert your rights clearly and respectfully. The goal is to protect yourself legally, not escalate the situation on the roadside.
Pulled Over, Questioned, and Searched? Take Action Now to Protect Your Rights
If a routine traffic stop led to a search, field sobriety tests, or even an arrest, you may have more legal options than you think. In Tennessee, officers must follow strict constitutional limits—and when they don’t, the evidence they gather can be challenged or thrown out.
At Barnes & Fersten, we focus exclusively on criminal defense, with a deep understanding of how traffic stops escalate into DUI and drug cases. Our team will examine every detail of your stop to determine whether your rights were violated and how to defend your case.
Don’t face serious charges without a defense strategy. Call us at 865-805-5703 or fill out our contact form for a free consultation. We serve clients in Knoxville and across East Tennessee, and we’re ready to fight for you.
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.
