It’s a Saturday night in Northern Virginia. You’re driving home after spending time with friends. Maybe you smoked a little earlier in the evening, or perhaps you took an edible yesterday to help you sleep. You feel completely sober. You are driving the speed limit, staying in your lane, and obeying all traffic laws.
Then, blue lights flash in your rearview mirror.
Panic sets in, not because you are drunk—you haven’t touched a drop of alcohol—but because you don’t know the rules for what comes next. With alcohol, everyone knows the golden number: 0.08% BAC. If you are under it, you are generally safe; if you are over it, you are going to jail. But when it comes to cannabis, the line is blurry. How much THC is too much in Virginia?
The answer might shock you. Unlike alcohol, there is no magic number. In Virginia, “too much” is whatever a police officer and a prosecutor can convince a judge it is.
If you are facing this uncertainty right now, understanding the law is your first line of defense. Experienced DUI defense attorneys know that these cases are won and lost on the nuances of science and the law, not just on a blood test result.
The Short Answer: There Is No “Legal Limit”
In many states like Colorado or Washington, lawmakers have established a “per se” limit for THC, typically set at 5 nanograms per milliliter of blood. If you test above that number, you are presumed impaired. Virginia has taken a different, more ambiguous path.
As of 2025, Virginia Code § 18.2-266 does not establish a specific nanogram limit for THC. There is no per se statute that says “5 nanograms equals guilty.” Instead, Virginia law operates on a “totality of the circumstances” basis. This means the Commonwealth does not need to prove a specific level of drug in your system; they only need to prove that you were “under the influence” to a degree that impaired your ability to drive safely.
This creates a dangerous legal gray area. You can have a very low level of THC in your blood and still be charged if an officer testifies that you looked or acted impaired. Conversely, a daily medical user might have high levels of THC in their blood while being perfectly sober due to tolerance, yet they still face the risk of a conviction because the law does not account for how frequent use affects blood concentration.
The Science of THC: Why It’s Not Like Alcohol
To understand why Virginia’s laws are so tricky, you have to understand the science of the drug itself. This is where many drivers—and even some lawyers—get confused.
Fat-Soluble vs. Water-Soluble
Alcohol is water-soluble. It mixes with your blood and water, affects you, and then leaves your system relatively quickly and predictably. If you blow a 0.00% on a breathalyzer, you generally don’t have alcohol affecting your brain.
THC (Tetrahydrocannabinol) is fat-soluble. When you consume cannabis, the THC is rapidly absorbed by the fatty tissues in your body (brain, heart, liver). It lingers there long after the “high” has worn off.
Active THC vs. Metabolites
This is the most critical distinction in a Virginia DUI case. When your body processes cannabis, it breaks it down into different compounds:
- Hydroxy-THC (Active THC): This is the psychoactive component. It is what makes you feel high. It typically spikes in the blood shortly after smoking and drops off significantly within 3 to 4 hours.
- Carboxy-THC (Metabolites): This is the inactive byproduct of your body processing the drug. It is non-psychoactive. It does not impair your driving, it does not alter your perception, and it does not slow your reaction time. However, it can remain detectable in your blood for days or even weeks after use.
The problem? Virginia blood tests often reveal both. If a prosecutor presents a lab report to a jury showing “Presence of Cannabinoids,” they may not clearly distinguish between the active drug that impairs you now and the harmless history of what you did last weekend. A skilled attorney like Scott C. Nolan knows how to force the Commonwealth to distinguish between these two, proving that a positive test doesn’t necessarily mean impaired driving.
How Police Build a Case Without a “Number”
Since they can’t rely on a Breathalyzer result flashing “0.08,” police officers in Virginia use a different toolkit to build a case against you. This usually involves three stages: observation, field testing, and chemical testing.
1. The Traffic Stop and “Odor”
For decades, the smell of marijuana was the “golden ticket” for police to search vehicles. However, Virginia law has evolved. Currently, the odor of marijuana alone is generally not enough to justify a search of a vehicle during a traffic stop.
However, do not be fooled: odor is still a massive piece of evidence in a DUI investigation. If an officer smells burnt marijuana, they will use it to justify asking you to step out of the car for field sobriety tests. They will testify that you had “bloodshot, glassy eyes,” “slurred speech,” or “delayed reactions”—all subjective observations that are hard to disprove without video evidence.
2. Standardized Field Sobriety Tests (SFSTs)
You know the drill: follow the pen with your eyes, walk a straight line, stand on one leg. These tests—the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand—were developed in the 1970s specifically to detect alcohol impairment.
They are notoriously unreliable for marijuana.
- The HGN Test: This test looks for involuntary jerking of the eye. While alcohol causes this jerking, cannabis typically does not. Yet, officers will often claim they saw “signs of impairment” in your eyes.
- Balance Tests: The Walk-and-Turn and One-Leg Stand test your balance and ability to follow instructions. While cannabis can affect balance in high doses, studies have shown that many sober people fail these tests due to nervousness, age, weight, or roadside conditions.
Recent studies, often referred to as “Green Lab” studies, have shown that police officers trained in these tests frequently identify sober people as “impaired” when they know the subject has consumed cannabis, highlighting a massive confirmation bias.
3. The Drug Recognition Expert (DRE) Protocol
In some Virginia jurisdictions, if an officer suspects drugs, they may call in a “Drug Recognition Expert” (DRE). This is an officer with specialized training to identify drug impairment. They follow a 12-step protocol that sounds scientific but is often highly subjective.
The 12-Step DRE Protocol:
- Breath Alcohol Test: To rule out alcohol.
- Interview of Arresting Officer: Getting the backstory.
- Preliminary Examination: Checking pulse (1st time) and pupil size.
- Eye Examination: HGN, Vertical Nystagmus, and Convergence.
- Divided Attention Tests: Romberg Balance, Walk and Turn, One Leg Stand, Finger to Nose.
- Vital Signs: Blood pressure, temperature, pulse (2nd time).
- Dark Room Examination: Checking pupil size in different lighting.
- Muscle Tone Examination: Checking for rigidity or flaccidity.
- Check for Injection Sites: Looking for needle marks (rare for cannabis).
- Subject’s Statements: Asking you to admit what you took.
- Opinion of the Evaluator: The DRE makes a guess on the drug class.
- Toxicology: Requesting a blood sample.
While this looks thorough, it relies heavily on the officer’s interpretation. For example, an elevated pulse (Step 6) is a sign of cannabis use. It is also a sign of being arrested and terrified. A good defense lawyer can dissect this protocol step-by-step to show where the officer’s “expert opinion” is actually just a guess.
The Trap of Implied Consent and Blood Testing
In Virginia, if you drive on a public highway, you have “impliedly consented” to have your blood or breath tested if arrested for DUI.
For alcohol, you take a breath test. For drugs, there is no breath test. This means you must submit to a blood draw.
Can You Refuse the Blood Test?
Technically, yes, you can physically refuse. However, the consequences are severe:
- First Refusal: This is a civil offense. You will lose your license for one year immediately. There is no restricted license (driving to work) allowed for a refusal conviction.
- Subsequent Refusals: If you have refused before or have a prior DUI, refusal becomes a criminal misdemeanor with jail time.
- Evidence of Guilt: Perhaps most importantly, the prosecutor can tell the jury that you refused the test because you knew you were guilty.
The “snapshot” Problem
Blood tests are accurate at measuring presence, but they are terrible at measuring timing. By the time you are arrested, transported to the station, processed, and taken to a hospital for a blood draw, hours may have passed since you were driving.
A blood test taken two hours after arrest tells us what is in your blood then, not necessarily what was affecting your brain when you were behind the wheel. The Commonwealth tries to use “retrograde extrapolation” to guess your levels at the time of driving, but this science is shaky at best for marijuana due to how differently it metabolizes in every person.
The Penalties: It’s Not Just a Traffic Ticket
Do not make the mistake of thinking a marijuana DUI is “less serious” than an alcohol DUI. In the eyes of Virginia law, they are identical.
First Offense (Class 1 Misdemeanor)
- Jail: Up to 12 months. While many first offenders avoid active jail time, it is always a possibility, especially if your driving was egregious or there was an accident.
- Fine: Mandatory minimum of $250, up to $2,500.
- License Suspension: 12 months. You may be eligible for a restricted license (with an ignition interlock), but this is discretionary.
- Ignition Interlock: Yes, even for a drug DUI where alcohol wasn’t involved, you may be required to install a breathalyzer in your car to get a restricted license. It makes little sense logically, but it is the law.
- VASAP: You must complete the Virginia Alcohol Safety Action Program (VASAP), which involves classes and probation.
The Hidden Collateral Consequences
For residents of Northern Virginia, the “hidden” penalties are often worse than the court’s punishment.
- Security Clearances: If you hold a Secret or Top Secret clearance, a drug-related conviction is a major red flag. It can lead to the immediate suspension or revocation of your clearance, effectively ending your career in government or contracting.
- Immigration: For non-citizens, drug offenses can be deportable crimes or render you inadmissible for future status adjustments.
- Child Custody: A drug DUI conviction can be used against you in family court proceedings.
Common Myths That Will Get You Convicted
- Myth 1: “I have a medical marijuana card, so I can’t be charged.”
False. A medical card allows you to possess and purchase cannabis. It does not allow you to drive under the influence. Just as a prescription for OxyContin doesn’t let you drive while sedated, a medical marijuana card is not a shield against DUI charges. In fact, admitting you have a card can sometimes hurt you, as it admits to the officer that you are a user.
- Myth 2: “I drive better when I’m high.”
False (legally). While you may feel more focused or paranoid (and thus drive slower), the law does not see it that way. Any deviation from “normal” driving—even driving too slowly—can be used as evidence of impairment.
- Myth 3: “If I drink a lot of water, I’ll pass the blood test.”
False. THC is stored in fat cells, not just your bloodstream. Drinking water might dilute your urine, but it has a negligible effect on the concentration of THC in your blood during a forensic draw.
How We Defend These Cases
Defending a marijuana DUI requires a specific strategy that attacks the unique weaknesses of these cases. A general criminal defense lawyer might treat this like a standard alcohol DUI, but a specialist knows better.
- Strategy 1: Attack the Stop
Everything starts with the lights in the rearview mirror. If the officer didn’t have a “reasonable articulable suspicion” to pull you over, the entire case falls apart. We scrutinize the dashcam footage: Did you actually weave? Was your tag really expired? If the stop was bad, the evidence is suppressed.
- Strategy 2: Attack the “Impairment”
We challenge the officer’s subjective observations.
Were your eyes red because of weed, or because it was 2 AM and you were tired?
Did you fail the balance test because you were high, or because you were asked to stand on one leg on the side of a sloping highway with semi-trucks flying by?
We often use the officer’s own body camera footage to show the jury that you looked, spoke, and acted sober, contradicting the police report.
- Strategy 3: Attack the Science
This is where Scott C. Nolan excels. We don’t just accept the blood test; we analyze it.
Does the report show active THC or just metabolites?
If the active THC is low (e.g., 1 or 2 nanograms), we argue that this is consistent with residual levels in a regular user, not acute impairment.
We can bring in expert toxicologists to testify that the levels found in your blood do not correlate with the driving behavior observed.
Conclusion: Don’t Face the Gray Area Alone
The question “How much THC is too much?” has no simple answer in Virginia. The law is currently written in a way that prioritizes prosecution over scientific accuracy. You can be convicted based on a police officer’s hunch and a blood test that reflects what you did days ago, not how you drove tonight.
However, the lack of a “per se” limit is also an opportunity. It means the Commonwealth must prove actual impairment. They cannot just point to a number and demand a conviction. They have to prove that the drug caused the bad driving.
That is a difficult burden to meet if they are challenged by an attorney who knows the science.
Scott C. Nolan has spent over 20 years defending Virginians against DUI charges. He is a member of the National College for DUI Defense and understands the specific interplay between toxicology, field sobriety testing, and Virginia law. He knows that a positive test is not a guilty verdict.
If you have been charged with a marijuana DUI, you are not just fighting a ticket; you are fighting for your license, your career, and your reputation. Don’t let a legal gray area determine your future.
Contact Scott C. Nolan today to schedule a consultation and start building a defense based on science and facts.
