Many people are surprised to learn that you can be charged with Driving Under the Influence (DUI) in South Carolina even if you haven't had a single drop of alcohol. Under state law, it is illegal to drive while "under the influence of alcohol, drugs, or a combination of both" to the extent that your ability to drive is materially and appreciably impaired.
This includes prescription medications—even when legally prescribed and taken exactly as directed by your doctor.
Prescription Medications That May Lead to DUI Charges
Common types of medications that can result in a DUI charge include:
Painkillers (e.g., Oxycodone, Hydrocodone)
Benzodiazepines (e.g., Xanax, Valium)
Sleep aids (e.g., Ambien)
Muscle relaxers
Medical marijuana (even with a valid card from another state)
Many of these drugs include warnings not to drive or operate heavy machinery due to their potential to cause drowsiness, delayed reaction times, or impaired judgment.
No Legal Limit Required
Unlike alcohol-based DUIs, where a blood alcohol concentration (BAC) of 0.08% or more creates a presumption of impairment, there is no fixed threshold for prescription drugs. This makes these cases highly subjective and dependent on:
Officer observations
Field sobriety test results
Toxicology reports
Statements made to police or EMS
Even small doses—well within prescribed limits—can still result in an arrest if police believe you're impaired. However, it's not illegal by itself to drive after taking medication, it's required that the government be able to prove material and appreciable impairment due to the medication.
Field Sobriety Tests and Drug Recognition
Standardized Field Sobriety Tests (SFSTs), including the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn (WAT), and One-Leg Stand (OLS), were developed and validated to detect impairment caused by alcohol—not drugs. These tests are not designed to reliably identify drug-related impairment and can often produce misleading results when used for that purpose.
Only a select group of law enforcement officers receive additional training through the Advanced Roadside Impaired Driving Enforcement (ARIDE) program. ARIDE-trained officers are taught how to detect drug-related impairment through additional testing methods, including the Modified Romberg Balance Test (which assesses internal clock and balance) and the Lack of Convergence Test (which evaluates the eyes’ ability to track inward).
ARIDE also introduces officers to the Drug Symptom Matrix, a tool used to classify observed impairment into categories such as central nervous system depressants, stimulants, hallucinogens, or cannabis. However, interpretation is highly subjective, and improper use can lead to incorrect assumptions about what substances are involved.
Attorney James R. Snell, Jr., has successfully completed ARIDE training himself, making him qualified to analyze police testimony and challenge improper or flawed drugged driving investigations.
Urine and Blood Testing After a Low or Zero Breath Test
When a driver provides a breath sample that registers 0.00 or a low BAC, officers may request a urine or blood test to check for the presence of drugs. Urine testing is often the preferred option due to its availability and lower cost.
However, urine tests do not reliably show what drugs a person is under the influence of at the time of arrest—they only show what substances may have been in the person’s system in the past. For example, marijuana can be detected in urine for days or even weeks after use, long after any impairing effects have worn off. This can result in innocent people being charged based on a positive drug screen that has no correlation with actual impairment.
Blood testing is more precise but is not always readily available and requires more rigorous legal procedures.
What Are the Defenses?
If you're facing a prescription drug DUI, you’re not without options. We can help you challenge:
Whether you were actually impaired at the time
The reliability of field sobriety or drug recognition tests
The accuracy and admissibility of toxicology results
The legality of the traffic stop or search
Statements made without proper Miranda warnings
Whether there is sufficient evidence you were appreciably and materially impaired as required by South Carolina's DUI law
Importantly, lawfully possessing a prescription is not a defense if you're impaired—but it may help show you were using the medication responsibly and not abusing it.
In most DUI cases in South Carolina, the government will not utilize any type of expert witness to prove impairment. Instead they rely on testimony from law enforcement, video recordings made by the officer, statements made by the defendant, and results of any breath, urine or blood testing. Prosecutions can be made on the officer's best "guess", creating opportunities for the defendant to raise important questions regarding the methodology used in the investigation and whether the actual evidence is sufficient to justify a DUI.
Avoiding Prescription DUI Charges
To reduce your risk of being charged:
Know how your medications affect you before driving
Avoid driving after taking new medications for the first time
Heed warning labels about drowsiness or operating machinery
Talk to your doctor about side effects
Never mix medications with alcohol
We Can Help
If you or someone you know has been arrested for DUI involving prescription drugs in South Carolina, our office can help you understand your rights and build a strong defense. These cases are complex and often misunderstood by prosecutors and juries alike.
Contact the Law Office of James R. Snell, Jr., LLC today for a confidential consultation. You can contact our office by calling (803) 359-3301.