A poor performance on a roadside balance exercise doesn’t automatically prove that someone was driving under the influence. Field sobriety tests are observations, not direct measurements of blood alcohol concentration, and their value depends on which test was selected, how instructions were given, the conditions at the scene, the officer’s training, and what video actually captured. For someone facing a DUI charge in Chattanooga, that roadside encounter can become the center of the case.
We’ve served Chattanooga since 2010, and our team brings more than 70 years of combined legal experience to criminal defense matters.
What Field Sobriety Tests Actually Measure
Standardized Field Sobriety Tests are roadside exercises developed under guidance from the National Highway Traffic Safety Administration (NHTSA). They’re designed to help an officer observe possible signs of impairment, but they don’t produce a blood alcohol result or establish guilt on their own.
The NHTSA SFST manual identifies three core exercises. Each has specific instructions, observable clues, and scoring principles that matter when the results are later reviewed.
The three standardized tests include:
- Horizontal Gaze Nystagmus: An eye movement test in which an officer looks for involuntary jerking of the eyes as they track a moving stimulus.
- Walk & Turn: A divided attention exercise that asks a person to complete a series of heel-to-toe steps, turn in a specified way, and return.
- One Leg Stand: A balance exercise that asks a person to raise one foot while following timing and counting instructions.
Officers may also ask a driver to recite the alphabet, count backward, or touch a finger to the nose. Those tasks can factor into an officer’s observations, but they aren’t part of the standardized battery and don’t carry the same NHTSA validation framework.
Tennessee’s implied consent law addresses chemical testing (breath or blood tests) rather than the three roadside exercises. A decision about whether to perform a field sobriety test and a decision about chemical testing raise different factual and legal questions, so the effect of a refusal requires a case-specific review.
Where Test Administration Goes Wrong
A standardized test only stays standardized when the officer follows required procedures closely enough for the observations to be meaningful. The recording and the report can reveal whether that happened.
Instructions, Demonstrations & Scoring
The Walk and Turn and One Leg Stand require more than a general instruction to balance or walk straight. The officer should explain and demonstrate the task, give the person a reasonable opportunity to understand the directions, and observe the correct clues during the appropriate portion of the exercise. A defense review can compare the officer’s report against body camera or dash camera footage, looking for an omitted demonstration, unclear timing, a clue marked in the report that doesn’t appear on video, or a driver faulted for not following an instruction that was never clearly given.
Conditions at the Test Location
Roadside conditions can affect even a sober person’s ability to complete balance and divided attention tasks. A sloped shoulder, uneven pavement, loose gravel, standing water, poor lighting, passing traffic, cold weather, or nearby emergency lights can all interfere with concentration and stability. Footwear matters too. High heels, work boots, sandals, or shoes with worn soles can make heel-to-toe walking and one-leg balancing more difficult, particularly on a surface that isn’t level, dry, and reasonably clear.
Physical, Medical & Language Factors
An injury, chronic pain, a balance disorder, inner ear condition, diabetes, fatigue, medication, advanced age, or anxiety can each affect test performance. None of these factors automatically invalidates a field sobriety test, but any one of them may provide a reasonable explanation for a particular observation when supported by records, video, or other evidence. Language is equally relevant: these exercises involve detailed, multi-step instructions, and if a person didn’t understand the officer’s directions, the question isn’t simply whether the person made a mistake. It’s whether the instructions were given in a way the person could reasonably follow.
How Tennessee Attorneys Challenge the Results
Field sobriety evidence can be challenged at different stages of a DUI case, and the right approach depends on what happened before, during, and after the roadside stop.
Probable Cause for Arrest
Probable cause requires facts that would lead a reasonable officer to believe an offense has been committed. If field sobriety testing contributed to the arrest decision, the defense can examine whether the officer had enough reliable information at that point, rather than relying on a later chemical test or information gathered after the arrest. Normal speech, a stable appearance on video, an unclear basis for the traffic stop, and improperly administered exercises can all affect how the full set of circumstances is understood.
Suppression of Evidence
A motion to suppress asks the court to exclude evidence obtained in violation of constitutional or legal rules. Depending on the facts, a challenge may concern the traffic stop itself, the detention, the arrest, a search, or evidence gathered afterward. Not every flaw in field sobriety testing creates a suppression issue. A problem with administration may affect whether the test result is persuasive, while a lack of reasonable suspicion or probable cause can raise a more direct legal challenge to evidence obtained after the stop or arrest.
Weight & Credibility at Trial
Even when field sobriety evidence is admitted, the defense can argue it deserves limited weight. Cross-examination can focus on the officer’s training, deviations from the NHTSA SFST manual, the testing surface, unrecorded portions of the encounter, and conflicts between the written report and video. Tennessee courts evaluate field sobriety evidence alongside the entire record rather than treating one roadside exercise as conclusive proof of impairment.
Why a Failed Test Doesn’t Automatically Prove DUI
A field sobriety test is one piece of a DUI investigation, not a determination of guilt. Its significance depends on the alleged driving conduct, speech, odor of alcohol, admissions, witness observations, chemical testing, and the reliability of the officer’s documentation. Alcohol and drug impairment investigations can also look different from each other. A drug-related allegation may involve additional evaluation or toxicology evidence, each of which must be assessed on its own facts.
A DUI defense attorney in Chattanooga can review whether the State’s theory matches the actual evidence. The question isn’t merely whether an officer wrote that a test was failed. It’s what was tested, how it was performed, what the recording shows, and whether the conclusions hold up.
What to Preserve After a Tennessee DUI Arrest
Evidence becomes harder to locate as time passes. Preserving information early gives the defense a clearer picture of the roadside encounter and helps surface questions that a written police report may not answer.
Materials worth preserving include:
- Video Recordings: Body camera footage, dash camera footage, jail video, and any nearby surveillance footage.
- Arrest Documents: The citation, arrest report, implied consent paperwork, bond paperwork, and any chemical test documents.
- Scene Details: The location of the exercises, weather, lighting, road surface, traffic conditions, and the footwear worn during testing.
- Medical Information: Records concerning injuries, balance conditions, prescribed medication, or other health issues relevant to the observations.
- Witness Information: Names and contact details for passengers or others who saw the stop or the testing.
In Chattanooga, misdemeanor criminal cases and traffic offenses may be handled in the Criminal Division of Hamilton County General Sessions Court. Felony matters may proceed through a preliminary hearing before being bound over to the grand jury, while Hamilton County Criminal Courts handle state criminal offenses ranging from misdemeanors to major felonies. The procedure depends on the charge and posture of the case, but the underlying review stays consistent: compare the report with the video, identify the procedures used, and assess the complete DUI investigation rather than a single roadside exercise.
A Roadside Test Is Evidence to Examine, Not a Verdict
Field sobriety testing can matter in a Tennessee DUI case, but it isn’t a mechanical pass-or-fail determination. The most useful early steps are preserving available recordings, keeping paperwork together, documenting conditions that affected performance, and reviewing the evidence before assumptions harden into conclusions.
Our team at Speek, Turner & Newkirk PLLC can review a DUI arrest using a team-based approach, with same-day appointments and translator access when needed. To discuss your case, contact us at (423) 436-8506 for a free initial consultation.