The “30-Day” Trap: Why You Can Get a DUI for Weed You Smoked Last Month

By: John Guidry

The problem with weed is that it tends to stay in your system for at least 30 days.

• The Science: THC is stored in the body’s fat cells. Compare that to cocaine, which is water-soluble and flushes out within 3 days.
• The Danger: If you are a weed smoker who has never been in trouble with the law, this physiological factoid should scare you.

The Scenario: Say you end up in a car accident with injuries. The police will take your blood to check for impairment. That joint you smoked two weeks ago at a party? It’s still there. Suddenly, you have handcuffs, a mugshot, and a DUI charge—even though you were stone-cold sober when the crash happened.

Did you test positive for marijuana even though you haven’t smoked in days?

Presence is not Impairment. Call John today at (407) 423-1117.

The Science: Active vs. Inactive Metabolites

Technically, it is a crime to operate a motor vehicle with any amount of drug in your body if that substance is impairing your driving.

• The Problem: How can a jury tell the difference between “Impaired Now” and “Smoked Last Week”?

The Two Types of THC:

1. Active THC (Hydroxy-THC): This is what makes you high. It causes psychoactive effects and can cause impairment. It usually leaves the blood within hours.
2. Inactive Metabolite (Carboxy-THC): This is the leftover trash. It has NO psychoactive effect. It does not make you high. But it stays in your system for 30+ days.

The Defense Strategy: In Florida, we file a Motion in Limine to suppress the results of any blood or urine test that only shows “Carboxy-THC.”

• The Argument: How can the prosecutor argue—with a straight face—that you were impaired by a chemical that cannot get you high? We ask the Judge to exclude this evidence as irrelevant.

The “Low Blow” & The Urine Test

So, where do most Orlando Marijuana DUIs come from? If there is no accident involved, they usually start with a “Low Blow.”

• The Setup: The officer thinks you are drunk. He arrests you and makes you blow into the Intoxilyzer 8000.
• The Result: You blow a 0.00 (or well under 0.08).
• The Reaction: The officer is confused. He thinks, “He looks messed up, but the machine says 0.00. Must be drugs!”

The Urine Request: He then demands a urine sample.

• The Privacy Violation: There is no privacy here. A government employee will watch you urinate into a cup to ensure you don’t fake it.
• The Trap: If you provide the sample, they will find that inactive metabolite from 3 weeks ago and charge you with DUI.

John’s 2026 Update: Roadside Swabs & The Medical Defense

Note: In the past, we relied on blood and urine. In 2026, the police want your spit.

1. The Rise of Oral Fluid (Saliva) Testing Because blood and urine are bad at proving recent use, police have shifted to Roadside Oral Fluid Testing (swabs).

• The Tech: Devices like the SoToxa or Dräger allow cops to swab your mouth at the car window.
• The Goal: These tests are designed to detect Active THC left in the mouth from recent smoking (usually within the last 4–6 hours).
• The Defense: While this avoids the “30-day” problem, these machines are notoriously prone to false positives from legal hemp products or contamination. We attack the reliability of the machine just like we attack the Breathalyzer.

2. The Medical Card is NOT a Shield Many clients ask: “John, I have a Medical Marijuana Card. Can I still get a DUI?”

• The Answer: YES. A prescription allows you to possess marijuana, not drive on it. You can get a DUI for Xanax or Vicodin, too.
• The Defense: However, the card does explain the presence of metabolites. We use the card to argue: “Ladies and gentlemen of the jury, of course he has THC in his blood; it is his daily medicine. That doesn’t mean he was impaired.” This shifts the focus back to the dashcam video: if you looked sober on video, the chemical test matters less.

3. The Failed Amendment & “Per Se” Limits Because the 2024 Recreational Marijuana Amendment failed, Florida never established a “Per Se” limit (like 5ng of THC).

• The Good News: This is actually good for defense. In states with a “5ng limit,” you are automatically guilty if you are over the limit. In Florida, the State always has to prove actual impairment. We don’t care about the number; we care about your driving.

Don’t Pee in the Cup

If you blow a 0.00 and the officer asks for urine, remember: You have the right to refuse. While refusing has consequences for your license, providing the sample hands them the “30-day” evidence they need to convict you.

Call me at (407) 423-1117. Let’s suppress the metabolites.

About John Guidry II

John Guidry II is a seasoned criminal defense attorney and founder of the Law Firm of John P. Guidry II, P.A., located in downtown Orlando next to the Orange County Courthouse, where he has practiced for over 30 years. With more than three decades of experience defending clients throughout Central Florida since 1993, Guidry has successfully defended thousands of cases in Orange, Seminole, Osceola, Brevard, Lake, and Volusia counties. He has built a reputation for his strategic approach to criminal defense, focusing on pretrial motions and case dismissals rather than jury trials.

Guidry earned both his Juris Doctorate and Master of Business Administration from St. Louis University in 1993. He is a member of the Florida Bar and the Florida Association of Criminal Defense Lawyers. His practice encompasses the full spectrum of Florida state criminal charges, with a particular emphasis on achieving favorable outcomes through thorough pretrial preparation and motion practice.

Beyond the courtroom, Guidry is a prolific legal educator who has authored over 400 articles on criminal defense topics. He shares his legal expertise through his popular YouTube channel, Instagram, and TikTok accounts, where he has built a substantial following of people eager to learn about the law. His educational content breaks down complex legal concepts into accessible information for the general public.

When not practicing law, Guidry enjoys tennis and pickleball, and loves to travel. Drawing from his background as a former recording studio owner and music video producer in the Orlando area, he brings a creative perspective to his legal practice and continues to apply his passion for video production to his educational content.