How Do Police Know if You’re High in a Virginia Drug DUI?

 Posted on June 18, 2026 in Drug DUI

Unlike alcohol, drugs do not show up on a breathalyzer. There is no roadside device that an officer can hand you that produces a magic number to show you are under the influence. Virginia law also does not set a universal legal limit for most controlled substances, the way it does for alcohol. 

That makes drug DUI cases both more complicated to prosecute and, in some ways, more complicated to defend. If you are faced with a drug DUI charge in Virginia in 2026, you need an experienced Chantilly DUI defense lawyer’s help. 

What Virginia Law Says About Driving Under the Influence of Drugs 

Virginia Code § 18.2-266 makes it illegal to operate a motor vehicle while under the influence of:

• Any narcotic drug

• Any combination of drugs that impairs your ability to drive safely

• Any other "self-administered intoxicant" 

This means prescription medications, marijuana, and illegal substances alike. It could even include over-the-counter cold medicine if taking it makes it unsafe for you to drive. 

For alcohol, Virginia sets a clear limit, which is a blood alcohol content of 0.08 percent or higher. Testing positive at a .08 or above creates a legal presumption of impairment, which means the law assumes you are too drunk to drive safely. 

For most drugs, however, no equivalent number exists that proves how messed up someone is. Instead, prosecutors must prove that whatever you took actually impaired your ability to drive. This requires more opinion-based evidence and more room for challenge.

Virginia law does set a limit for certain substances, including cocaine and methamphetamine. Even a very small amount set by law of these drugs in your blood can let prosecutors argue you were under the influence, even if you didn’t seem impaired. An attorney who knows Virginia's DUI statutes can help you understand exactly which standard applies to your case and fight the prosecutor’s accusations. 

How Do Officers Know if You’re on Drugs at a Traffic Stop?

When a police officer pulls someone over and thinks maybe the person is high rather than drunk, this is what usually happens: 

Analyzing Your Behavior

The officer first observes your behavior, speech, and physical appearance. Signs they are trained to look for include:

• Bloodshot or glassy eyes

• Slowed or slurred speech

• Unusual pupil size

• The smell of marijuana

• Impaired coordination

• Delayed or confused responses to questions

Field Sobriety Tests

If the officer suspects impairment, they may require that person to take standard field sobriety tests. These include walk-and-turn, the one-leg stand, and the horizontal gaze nystagmus test. These tests were originally designed to detect alcohol use, so their reliability in drug impairment cases is a legitimate area of scientific debate.

Calling in a Drug Recognition Expert

If an officer believes a driver is impaired by drugs but alcohol does not appear to be the cause, a Drug Recognition Expert may be called to the scene or involved later in the investigation. DREs are officers who have completed specialized training in a 12-step evaluation protocol developed by the National Highway Traffic Safety Administration.

The DRE evaluation includes checking your pulse, eye response, muscle tone, and other physical indicators to figure out which drug someone has taken. 

Blood Tests and Virginia Drug DUIs 

Because a breathalyzer can’t detect drugs, blood testing is the primary way Virginia confirms drugs in someone’s system. If you are arrested on suspicion of drug DUI, you will be asked to submit to a blood draw under Virginia's implied consent law. Refusing to take a blood test has legal consequences, including automatic license suspension.

A positive blood test does not automatically prove you’re impaired. Many substances, including marijuana, are detectable in the bloodstream for days or weeks after use. The gap between presence and impairment is one of the most important issues in drug DUI defense, and it is one that an experienced attorney will examine closely.

What Happens if You’re Not a Citizen and You Get a Drug DUI Charge in Virginia? 

For non-citizens, a drug DUI conviction in Virginia carries serious risks beyond the normal legal consequences. Depending on your immigration status and the specific charge, a conviction can affect:

• Visa renewals

• Green card applications

• Grounds for removal proceedings

If you are not a U.S. citizen and you are facing a drug DUI charge, you need a DUI defense attorney who really understands how immigration law works with the criminal justice system. At Arrested for a DUI, LLC, our team is very good at this.

Call a Vienna Drug DUI Defense Lawyer Today

At Arrested for a DUI, LLC, our Chantilly, VA drug DUI defense attorneys bring more than 30 years of combined experience to DUI defense in Northern Virginia. We work closely with the Hispanic community because we understand how criminal charges can trigger immigration consequences. Call us today at 301-479-5466 for a free consultation.

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