Driving under the influence isn’t limited to alcohol. In Kentucky, marijuana use behind the wheel can lead to a DUI—regardless of your medical card or level of impairment.

Marijuana and DUI Laws in Kentucky

Kentucky law prohibits operating a motor vehicle while under the influence of any impairing substance. While the state has not fully legalized recreational cannabis, medical marijuana was legalized in 2023 and is expected to be fully implemented by 2025. However, the legal status of marijuana does not change the rules of the road. Even if someone has a valid prescription or is using marijuana legally under medical supervision, driving under its influence is still grounds for a DUI charge.

Under Kentucky Revised Statutes (KRS) § 189A.010, a person can be charged with DUI if they are:

• Under the influence of alcohol,
• Under the influence of any other substance that impairs driving ability (including marijuana),
• Or have a controlled substance in their blood as measured by a scientifically reliable test.

This means proof of impairment is not the only route to a conviction—simply having detectable levels of THC in the blood can be enough under certain conditions.

How Kentucky Law Treats Marijuana DUIs Compared to Alcohol

Alcohol-related DUIs in Kentucky are based on blood alcohol concentration (BAC), with the legal limit set at 0.08% for adults. With marijuana, there is no defined threshold. Instead, authorities may rely on:

• Blood or urine tests to detect THC,
• Observations by law enforcement (such as field sobriety tests),
• And expert testimony about the driver’s impairment.

Unlike some states that set a per se limit (like 5 nanograms of THC per milliliter of blood), Kentucky uses a zero-tolerance approach for controlled substances, including marijuana, unless you are covered under narrow medical exceptions. Even then, impairment can still lead to charges.

Medical Marijuana Doesn’t Grant Driving Privileges in Kentucky

Some drivers mistakenly believe that having a medical marijuana card insulates them from DUI prosecution. It doesn’t.

Kentucky’s new medical cannabis law (Senate Bill 47) allows qualifying patients to use marijuana for certain medical conditions. However, the law clearly prohibits driving under the influence of marijuana, regardless of medical need.

Even if marijuana was legally obtained and used for a diagnosed condition, the state’s position is straightforward: a medical card is not a free pass to drive while impaired.

How Police Determine Marijuana Impairment

Unlike alcohol, which can be reliably tested with a breathalyzer, marijuana detection is more complicated. THC—the psychoactive component of cannabis—can remain in the bloodstream long after its impairing effects have worn off. This creates legal and scientific challenges.

To build a case for a marijuana DUI, Kentucky law enforcement typically relies on:

• Drug recognition experts (DREs): Officers trained to detect drug impairment based on physical signs like eye movement, coordination, and pupil size.
• Field sobriety tests: While not marijuana-specific, these are used to observe behavior and coordination.
• Blood or urine tests: Used to confirm THC presence but cannot always indicate current impairment.

This combination of subjective and objective evidence makes marijuana DUIs harder to prosecute than alcohol-related DUIs—but not impossible.

Penalties for a Marijuana DUI in Kentucky

The penalties for a marijuana-related DUI mirror those for alcohol and escalate with repeat offenses. For a first offense, drivers may face:

• Up to 30 days in jail,
• Fines ranging from $200 to $500,
• License suspension for 30 to 120 days,
• Mandatory substance abuse education or treatment.

Aggravating factors—such as driving with a child in the car, causing an accident, or refusing chemical testing—can increase penalties significantly.

Repeat offenses carry heavier consequences, including longer jail time, steeper fines, and longer license suspension periods.

Zero Tolerance for Drivers Under 21

Kentucky enforces a strict zero-tolerance policy for underage drivers. If a driver under 21 has any measurable amount of marijuana or alcohol in their system, they can face DUI charges.

This policy reflects the state's efforts to deter young drivers from mixing substances and driving, even if they don't feel impaired.

Marijuana Metabolites and Post-Use Charges

Because THC remains in the body for days or even weeks after use, drivers could potentially face charges even if they were not impaired at the time of arrest. Kentucky law allows for prosecution based on the presence of marijuana metabolites, especially in cases involving accidents or erratic driving behavior.

This raises concerns about fairness and accuracy, but as of now, the law does not require proof of current impairment—just a scientifically reliable test confirming the presence of THC or its byproducts.

Fighting a Marijuana DUI Charge in Kentucky

Anyone charged with a marijuana DUI in Kentucky should seek legal representation immediately. Mounting a strong defense may involve:

• Challenging the reliability or timing of the THC test,
• Questioning the qualifications or findings of the DRE officer,
• Highlighting alternative explanations for impairment-like symptoms (fatigue, medical conditions, etc.).

Since Kentucky lacks a per se THC limit, context matters—and an experienced attorney may be able to argue that the presence of THC did not equate to actual impairment at the time of the incident.

Conclusion

Driving after using marijuana—whether recreationally or medicinally—can absolutely result in a DUI charge in Kentucky. The state takes an aggressive stance, applying a zero-tolerance approach toward drugged driving. Even without clear signs of impairment, the mere presence of THC in your system could put you at risk. With significant penalties at stake, it’s essential to understand your rights and the limits of the law before getting behind the wheel.

Need Legal Help? Brandon J. Broderick, Attorney at Law is One Phone Call Away

Navigating Kentucky laws can be challenging. If you've been injured in a DUI or suspected DUI accident, the lawyers at Brandon J. Broderick, Attorney at Law can help. We're available 24/7 to help you understand your legal options, gather necessary evidence, and build a strong case to secure the settlement you deserve.

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