DUI Laws: Driving Under the Influence of Drugs and Controlled Substances

The majority of DUI arrests relate to drunk driving. However, a driver can also face DUI charges for operating a vehicle while under the influence of controlled substances, drugs, or nearly any other impairing substance. Even in situations where a driver's use of a medication or drug was lawful (because of a prescription or otherwise), there's no immunity from state DUI laws

This article explains how state DUI laws apply when a driver is under the influence of controlled substances, drugs, or other intoxicating substances.

Types of Drugged Driving Laws

In every state, you can be convicted of a DUI offense for operating a vehicle while actually under the influence of (impaired by) alcohol or with a blood alcohol concentration (BAC) of .08% or more (.05% in Utah). Generally, a DUI based on BAC is called a "per se DUI."

In many states, it works the same way with drugs—drugged driving charges can be based on actual impairment or having a prohibited amount of a drug in your system. However, some states don't have per se drug DUI laws. In these states, a drug DUI conviction must be based on actual driver impairment.

DUIs Based on Drug Impairment

Every state has laws prohibiting the operation of a motor vehicle while under the influence of an impairing substance. To obtain a conviction, the prosecutor must prove that the offender was operating (or in actual physical control) of the vehicle and was actually impaired by a foreign substance. The definition of impairment varies between states but generally means that the driver's physical or mental facilities are adversely affected to a noticeable or perceptible degree.

To prove impairment, the prosecutor often uses the driver's blood test results (showing what drugs were in the driver's system) along with expert testimony about how the consumed substances might affect a person's ability to drive safely. The arresting officers might also testify as to their observations. For example, an officer might explain on the stand that the driver was off-balance, had slurred speech, and was unable to perform field sobriety tests. Officers generally receive special training on how to identify and test for possible drug impairment, which they might explain in their testimony.

Per Se Drug DUIs

Per se drug DUI laws prohibit the operation of a motor vehicle with a certain level of drugs in your system. Per se drug DUI laws simply list the substances that can lead to a conviction along with the prohibited concentrations. For example, a per se DUI law might specify it's illegal to drive with a THC (the main psychoactive component in marijuana) concentration of 5 nanograms/milliliter or more in your blood.

A few states have zero-tolerance laws on schedule I drugs. In these states, a driver can be convicted of a DUI for having any measurable amount of an illicit drug (heroin, cocaine, and methamphetamine being some of the most common) in his or her system.

A driver with an unlawful drug concentration can be convicted of a DUI offense without proof of actual impairment.

Substances That Count as "Drugs"

The majority of states cast a wide net when defining what substances can lead to a DUI conviction. Generally, the list of substances includes controlled substances, inhalants, prescription medications, cannabis, over-the-counter medications, and any other substance that can cause impairment.

Prescription Drugs Are Sometimes Treated Differently

Generally, driving while impaired by any substance is illegal. So the fact that a driver had a valid prescription for the drug that caused impairment generally isn't a defense to an impairment-based DUI charge.

However, in some states, having a prescription can be a valid defense to a per se DUI charge. To establish this defense, the driver normally needs to show he or she used the medication as prescribed by a medical professional.

Drugged Driving Penalties

The penalties for a drugged driving offense are generally identical to those for a drunk driving conviction. Generally, a convicted offender can expect possible jail time, fines, and license suspension. The penalties are typically more severe for repeat offenses or offenses involving certain aggravating circumstances.

Some states also have special treatment-based DUI programs such as DUI court and first-offender programs. Participants in these programs might be able to avoid some of the penalties they'd otherwise face for a DUI offense.