Evidence in DUI Cases

As in all criminal cases, the prosecution is charged with proving guilt beyond a reasonable doubt before a defendant can be convicted of driving under the influence in Tennessee and Georgia. In order to prove this guilt, the prosecutor will rely on the evidence collected against a defendant, typically by the arresting officer. In both Tennessee and Georgia, driving under the influence may be proven by circumstantial evidence – see Pecina v. State, 274 Ga. 416, 554 S.E.2d 167 (2001) and State v. Ralph, 347 S.W.3d 710 (Tenn. Crim. App. 2010). This means that each piece of evidence, including circumstantial evidence, must be carefully considered in the preparation of a comprehensive defense strategy to a DUI charge. Let’s break down the different types of evidence the prosecution will use to attempt to prove a defendant is guilty of driving under the influence!

Driving ObservationsEvidence in DUI Cases

Most DUI cases begin with the arresting officer’s observation of the defendant’s driving. Officers will use traffic infractions such as speeding, failure to maintain lane, or running a red light as probable cause to initiate the traffic stop that leads to a DUI arrest, as well as evidence to demonstrate that the driver’s ability to operate a motor vehicle was impaired.

This piece of evidence becomes complicated when the defendant in a DUI case was involved in an automobile accident. In these situations, the arresting officer does not always observe the defendant driving. Therefore, the officer will have to first prove that the defendant was indeed the person driving the wrecked vehicle, and then that said driver was impaired. Officers in Tennessee and Georgia can also make a DUI arrest when the defendant was sleeping or parked in a car while under the influence of alcohol or drugs, as long as they can prove that the defendant was in physical control of the vehicle. For example, if the defendant was asleep in the driver’s seat of a vehicle in a public parking lot, the officer may decide to arrest them for DUI.

An officer’s observation of a defendant’s driving, or physical control of a motor vehicle, is the vital first step in a DUI investigation, and can make or break an officer’s probable cause to conduct an arrest. At Best & Brock, we are dedicated to defending our client’s constitutional rights by investigating – and challenging if necessary – the validity of the initial traffic stop in each case we encounter.

Physical Observations

Once an officer has initiated a traffic stop, they will attempt to determine if the driver is intoxicated by taking note of their physical appearance. Common indicators that a driver may be under the influence include bloodshot or glassy eyes, fumbling fingers, and disheveled hair or clothes.

However, each of these physical observations may have alternative explanations. An individual with a neurological disorder, such as Parkinson’s Disease, may experience fumbling fingers unrelated to alcohol or drugs. An individual who works long shifts may be expected to have bloodshot eyes induced by exhaustion. Best & Brock’s criminal defense attorneys explore alternative explanations with our clients to ensure that their stories are heard.

Field Sobriety Tests

Officers typically proceed with a DUI investigation by requesting the suspect participate in a standardized field sobriety test. Throwback to our 2019 blog on roadside sobriety tests! The most common tests are the Horizontal Gaze and Nystagmus, Walk and Turn, and One Leg Stand tests. However, officers can conduct other tests if necessary. Officers who have training in drug recognition are likely, if they suspect a driver is under the influence of drugs, to conduct tests designed to detect drug use. These tests include the Finger to Nose and Modified Romberg Balance tests, which are divided attention tests that aim to disclose evidence of impairment due to drug use.

The results of field sobriety tests are often the crux of an officer’s arrest decision. In their arrest narratives, officers will explain the defendant’s performance on field sobriety tests as evidence that they had probable cause to arrest the defendant for driving under the influence.

Although field sobriety tests are supposed to be standardized, officers do not always instruct or conduct the tests according to protocol. This can produce results that unfairly inform an arrest decision. For this reason, we carefully review any field sobriety tests performed by our clients for indications that the officer deviated from the standardized procedure. By analyzing each case in great detail, we’re able to reveal discrepancies that create a window to question the officer’s decision to arrest a defendant.


At any stage in a DUI arrest, the defendant may make statements that will be used against them in the court of law. Of course, a defendant’s admissions to drinking and/or drug consumption are valuable evidence in a DUI case. One of the first questions officers will ask when they’ve pulled over a driver is whether they’ve drank any alcohol or consumed any drugs. The driver may choose not to answer, utilizing their Fifth Amendment right against self-incrimination. Officers will put this in their investigative notes, but they should not ask any further questions until the right to remain silent has been waived.

Certain statements may not be admissible as evidence. Once an individual is in custody, law enforcement officers are required to inform them of their Miranda rights before asking any questions. At Best & Brock, we move the court to suppress any inadmissible statements made by our clients as part of our comprehensive defense strategy.

Chemical Tests

Chemical tests are some of the more concrete evidence in DUI cases – but notice that we only say “more” concrete, because these tests are not infallible!

A sample of a defendant’s blood or breath may provide evidence of a certain amount of alcohol or other intoxicating substance being present in their body at the time of testing. In DUI cases where the officer suspects drugs may be impairing the driver’s ability to operate a vehicle, a blood sample will likely be sent off to the state’s bureau of investigation for chemical testing. In DUI cases involving alcohol, the officer could send off a blood sample, or request that the defendant blow into a breathalyzer machine.

When an officer requests a sample of your blood or breath for testing, the implied consent law is invoked. (Check out our blog on implied consent for a deep dive into this topic!) In short, this means that a driver has given the state implied consent to test their blood or breath for the presence of intoxicants when there is probable cause to believe that the driver was driving under the influence. The driver still has the opportunity to revoke their implied consent prior to testing, but this may result in penalties including the suspension of the driver’s license.

Open Containers or Illicit Substances/Drug Paraphernalia

Once a driver has been arrested for DUI, officers will typically conduct a probable cause search of their car in the interest of unveiling any further evidence of crime. If the officer finds drugs, drug paraphernalia (such as pipes and lighters), or open alcoholic containers, these items will be documented as evidence against the driver. Not only will these items be used as evidence to support the DUI charge, they may also introduce separate charges (i.e., violation of open container law or possession of drug paraphernalia) against the defendant.

Not all items that officers believe to be evidence of a crime are truly incriminating, though. For example, officers may find legal hemp in a driver’s car and mistakenly charge that driver with possession of marijuana. Best & Brock helps our clients challenge each piece of physical evidence alleged by officers, demonstrating that these items are not evidence of illicit behavior when possible.

Arrest Footage

Nowadays, it’s becoming increasingly common for law enforcement officers to wear body cameras and affix dash cameras to their cars. This means that their observations of a defendant’s driving, physical appearance, performance on field sobriety tests, and other evidence obtained at the time of the arrest will be preserved on video. While these videos can be incredibly useful to building a defense strategy, their contents may also be harmful to a defendant’s defense. Best & Brock’s criminal defense attorneys review each client’s arrest videos to identify any legal issues which will empower us to secure a unique resolution to each case. Piece by piece, we challenge the evidence presented by officers and prosecutors to demonstrate the merits of our client’s case.

Best & Brock Can Help

Even when the evidence against you feels overwhelming, we will help you find hope and reach a fair resolution to your DUI case. If you’ve been charged with DUI in Tennessee or Georgia, reach out to Best & Brock at (423) 829-1055 or by filling out our online contact form to set up a FREE consultation with one of our attorneys. It’s our honor to defend your rights and your future!