What Evidence Does the Prosecution Use in a DUI Case?

Posted: May 22, 2026

A driving under the influence (DUI) charge in Tennessee can lead to jail time, license suspension, and a permanent criminal record that affects employment and insurance for years. If you have been arrested, preserve your rights by staying silent and retaining counsel immediately. At Andrew C. Beasley, PLLC, our attorneys handle DUI defense cases by dismantling each piece of evidence the prosecution presents.

Chemical Test Results (BAC)

Blood alcohol concentration (BAC) results from breath, blood, or urine tests form the centerpiece of most DUI prosecutions. A reading of 0.08% or higher creates a presumption of impairment, though the accuracy of these tests depends on proper calibration, administration, and handling by the Metropolitan Nashville Police Department.

Field Sobriety Tests (FSTs)

Field sobriety tests (FSTs) are standardized exercises officers use at the roadside to gauge impairment before making an arrest. The three tests approved by the National Highway Traffic Safety Administration (NHTSA) and commonly introduced at trial are:

Horizontal gaze nystagmus (HGN)
Walk-and-turn test
One-leg stand test

Audio and Video Recordings

Dashcam and bodycam footage from the traffic stop often becomes a central exhibit at trial. Recordings capture your driving, speech, balance, and interactions with officers, and they can either support or contradict the officer’s written account depending on what the cameras show.

Officer Observations

The arresting officer’s testimony about what you looked like, smelled like, and sounded like carries significant weight with juries. Officers typically document specific observations that the prosecution uses to establish probable cause and impairment:

Bloodshot or watery eyes
Slurred speech
Odor of alcohol on the breath
Fumbling with documents
Swaying or unsteady balance
Admissions of drinking
Erratic driving patterns

Statements and Confessions

Anything you say to officers before, during, or after arrest can be used against you in court. Even statements that seem harmless, like admitting to having one drink hours earlier, often appear in police reports as evidence of impairment and are introduced at trial to support the prosecution’s theory.

Expert Witness Testimony

Prosecutors frequently call toxicologists and law enforcement experts to explain BAC calculations, retrograde extrapolation, and the effects of alcohol on the body. Qualified defense experts can challenge these conclusions by exposing flaws in methodology, testing equipment, or the assumptions behind the analysis.

DUI Defense in Tennessee

A strong DUI defense challenges each piece of evidence the prosecution presents under Tennessee Code Annotated § 55-10-401 and related statutes. Common defense strategies are as follows:

An illegal traffic stop lacked reasonable suspicion
Improper administration of field sobriety tests
Breathalyzer calibration or maintenance errors
Blood test chain of custody failures
Medical conditions affecting test results
Rising BAC at the time of driving
Miranda violations during questioning
Inaccurate officer observations

Building a Strong Defense Against DUI Evidence

A DUI arrest can feel like the ground has shifted under your feet, and the hours after an arrest matter more than most people realize. Our firm has two former district attorneys who understand exactly how prosecutors build these cases, and that perspective shapes the defense we construct for you. Call Andrew C. Beasley, PLLC at 615-846-9889 to schedule a free consultation with a DUI defense lawyer in Nashville who will carefully examine the evidence against you.