Studies show a measurable rise in marijuana-involved crashes in states that legalized recreational use, though researchers still debate the exact cause.
The Highway Loss Data Institute found a roughly 4% rise in collision claims in states after retail marijuana sales began. The Insurance Institute for Highway Safety reported a 6% rise in injury crash rates in those same states.
Missouri data is still early, but the state appears to be following the same national pattern of more THC-positive drivers appearing in post-crash testing.
Researchers note that part of this increase comes from better detection. Police are now more likely to test for THC after a crash, which means more drivers show up as THC-positive in the data, even if they were not actively impaired at the time of the collision.
What Do Insurance Claims Show After Legalization?
Collision claim frequency is the number of crash-related insurance claims filed compared to the total number of insured vehicles on the road. When this number goes up, it means more crashes are happening relative to the number of drivers.
After recreational marijuana sales began in legalization states, the Highway Loss Data Institute tracked a consistent rise in crashes. That pattern held across multiple states and time periods, which makes it harder to dismiss as coincidence.
Does THC-Positive Mean the Driver Was Impaired?
This is one of the most important distinctions to understand. THC is the active compound in marijuana that causes impairment. It can stay in a person’s system for days or even weeks after the effects have completely worn off.
Here is what that means in practice:
- THC-positive: A test found detectable THC in the driver’s blood, urine, or oral fluid.
- Impaired: The driver was actually under the influence and unable to drive safely at the time of the crash.
- Why it matters: A driver can test positive for THC without being impaired during the crash, which makes these cases harder to prove.
What Happens When Alcohol and Marijuana Are Combined?
Combining alcohol and marijuana is significantly more dangerous than using either substance alone. The two work together to slow reaction time, distort judgment, and reduce a driver’s ability to control a vehicle.
Drivers who mix both substances are far more likely to cause a serious crash. When this combination is involved in an accident, it often strengthens your legal rights after a DWI crash and supports the case for the injured victim.
Why Marijuana Impairment Is Hard to Measure
Unlike alcohol, there is no roadside breathalyzer for THC. Blood tests can detect the presence of THC, but they cannot reliably tell us how impaired a driver actually was at the time of the crash.
A regular medical marijuana user might have high THC levels in their blood but feel no effects at all. A first-time user might be severely impaired with comparatively low levels. This inconsistency makes measuring marijuana impairment one of the biggest challenges in drugged driving cases.
Does Missouri Have a THC Legal Limit for Drivers?
No. Missouri does not have a per se THC limit for driving. A per se limit means a specific number that automatically establishes legal impairment, similar to the 0.08% blood alcohol limit for drunk driving.
Some states, such as Colorado, use a 5 nanograms per milliliter limit as a threshold. Missouri prosecutors instead rely on observed signs of impairment rather than a number on a test.
How Long Can THC Affect Driving?
The method of use significantly changes how quickly marijuana takes effect and how long it impairs driving. Tolerance, dose, and potency also affect these windows.
| Method | Onset of Effects | Impairment Duration |
| Smoking or vaping | Within minutes | 3 to 4 hours |
| Edibles | 30 minutes to 2 hours | Up to 8 hours or longer |
How Do Police Document Marijuana Impairment in Missouri?
Officers use standard field sobriety tests at the scene to look for signs of impairment. If they suspect drug use, they may call in a Drug Recognition Expert, or DRE. A DRE is an officer with specialized training to identify which type of substance is impairing a driver. Police may also request a blood draw to confirm the presence of THC.
Is Driving High Illegal in Missouri?
Yes. Driving under the influence of marijuana is a DWI in Missouri, even if you legally purchased the cannabis. A DWI stands for Driving While Impaired and carries serious consequences.
A first-offense marijuana DWI can result in:
- Up to 6 months in jail
- A fine of up to $500
- A 30-day driver’s license suspension
Penalties increase significantly with repeat offenses or if the impaired driver caused injury to someone else. Having a medical marijuana card is not a legal defense to a DWI charge.
How We Prove Drugged Driving in a Missouri Claim
Because Missouri has no THC threshold, building a strong civil claim requires layered evidence from multiple sources. This is exactly the kind of case our team handles every day.
We fight to prove impairment even when there is no clean test number to point to. Our job is to hold the impaired driver accountable for what they did to you.
What Scene and Vehicle Evidence Helps Your Case?
Physical evidence from the crash scene is often the foundation of a drugged driving claim. We look for:
- Police crash reports and any DRE evaluations completed at the scene
- Event Data Recorder data, sometimes called black box data, which records vehicle speed and braking before impact
- Skid marks, debris patterns, and crash reconstruction analysis
- Photos of drug paraphernalia or open cannabis packaging found in the other driver’s vehicle
How Do Toxicology Results and Driver Admissions Get Used?
Blood and urine toxicology results can support the argument that the driver had THC in their system at the time of the crash. We also look for any statements the driver made to police officers or emergency responders at the scene.
When relevant, we subpoena hospital toxicology reports to get a complete picture of what was in the driver’s system.
How Do Video Footage and Eyewitnesses Strengthen Your Claim?
We track down dashcam footage, traffic camera recordings, and surveillance video from nearby businesses. This footage can show exactly how the driver was behaving in the moments before the crash.
Eyewitness statements are equally valuable. If someone saw the driver swerving, ignoring traffic signals, or appearing disoriented after the crash, that testimony adds significant weight to your claim.
What You Should Do After a Suspected Drugged Driving Crash
The steps you take in the first hours after a crash can protect both your health and your legal claim. Acting quickly matters.
What to Do in the First 72 Hours
Take these steps as soon as you are able:
- Call 911 to get police and medical help to the scene immediately.
- Get a full medical evaluation, even if your injuries feel minor at first.
- Document the scene with photos if you are physically able to do so.
- Save the police report number and any information from the other driver.
- Contact our Missouri car accident attorneys before you speak to any insurance company.
What to Avoid Saying to Insurance Companies
Insurance adjusters are trained to limit what they pay out. Protect your claim by following these rules before you speak with anyone:
- Do not guess about fault: Stick only to the facts you know for certain.
- Do not give a recorded statement: Talk to us first before allowing any recording.
- Do not accept a quick settlement offer: Early offers rarely cover your full damages, including future medical costs.
How We Build and Protect Your Case
We handle the full investigation, work with expert witnesses, and manage all insurance negotiations while you focus on getting better. If the insurance company refuses to offer fair compensation, we take them to court.
Beck & Beck Missouri Car Accident Lawyers is the only law firm in Missouri focused solely on auto accident law. With decades of experience and a proven track record of securing compensation for our clients, we know how to protect your rights and your future.
Injured by a Drugged Driver? Contact Us Today
You should not be left paying for injuries caused by someone who chose to drive impaired. We offer free case evaluations, and you pay no fees unless we win.
Our team is available 24 hours a day, 7 days a week, to answer your questions. Contact Beck & Beck Missouri Car Accident Lawyers today by phone or through our online contact form to get started.
FAQ
Does Missouri Prosecute Marijuana DWI Without a Blood Test?
Yes. Missouri prosecutors can pursue a marijuana DWI charge based entirely on an officer’s observations of impaired behavior, without relying on a blood test result.
Does a Medical Marijuana Card Protect You From a DWI in Missouri?
No. A medical marijuana card allows you to legally possess and use cannabis, but it does not give you the right to drive while impaired.
How Long After Using Marijuana Is It Safe to Drive in Missouri?
You should wait at least 4 hours after smoking and 8 or more hours after consuming edibles, and longer if you still feel any effects at all.
What If the Driver Who Hit You Mixed Alcohol and Marijuana?
Mixing alcohol and marijuana dramatically increases crash risk and reckless behavior. This combination often strengthens your claim for full compensation, including punitive damages.
How Long Do You Have to File a Drugged Driving Injury Claim in Missouri?
Missouri’s personal injury statute of limitations is generally 5 years from the date of the crash, but acting sooner protects critical evidence.
Can You Recover Punitive Damages After a Marijuana DWI Crash?
Yes. When a driver’s decision to drive impaired shows a reckless disregard for the safety of others, Missouri law may allow you to seek punitive damages in addition to compensation for your injuries and losses.
