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Marijuana and DUI under Florida's Impaired Driving Laws

DUI from Marijuana

It should be no surprise that the most commonly detected illegal substance in the urine is marijuana (sometimes in combination with other drugs or alcohol), since marijuana is the most widely used illegal drug in the State of Florida. Both blood and urine tests can detect cannabinoids which are THC and the metabolites of TCH.

Many people contact us after being arrested for DUI. In many of these cases the person blew just under the legal limit or registered a 0.00 reading which indicated that they had not consumed any alcohol. However, the officer nevertheless requested a urine or blood test because the officer suspected the driver was impaired by marijuana, either because the odor of marijuana lingered in the vehicle or on the driver, or because marijuana was found in the vehicle.

Tampa DUID and DUI Marijuana Attorneys

The test performed in Florida are very BAD at showing whether a driver is impaired at the time of driving. If you have been arrested for driving under the influence of marijuana or drugs in the greater Tampa Bay area for Tampa and Hillsborough County, FL, then contact an experienced DUID defense attorney to help you fight your charges.

The attorneys at the Sammis Law Firm on the NORML Legal Committee which fights for the reform of marijuana laws throughout Florida and the rest of the country. Driver who are NOT impaired should not be convicted of DUI just because trace amounts of THC or other marijuana metabolites in their system.

Urine and Blood Tests Showing Trace Levels of Cannabinoids after a DUI Arrest

The urine test and blood tests can detect cannabinoids for more than two (2) weeks after consumption for the casual user of marijuana or for up to one month with the chronic user of marijuana. Different urine tests detect different types of metabolites of cannabis.

The main active component of cannabis is a metabolite of delta-9-THC called 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acide (9-carboxy-THC). Scientific studies show that more than 80 percent the metabolite delta-9-THC is eliminated from the body within 5 days after marijuana is ingested.

THC in the Blood or Urine Does Not Always Prove Impairment or DUI

In most cases, urine testing is not a reliable method for measuring the level of THC in the driver's system because the urine test can not pinpoint when the marijuana was consumed. THC is the main psychoactive ingredient in cannabis which can linger in a person's system long after the "high" or impairing effects have passed.

Even a single instance of smoking marijuana can leave metabolites in the urine for at least 10 days or even longer depending on the quantity of marijuana consumed. Even if the level of THC is high, the driver could have smoked cannabis several days before driving when no impairment is possible. Epidemiological data suggests that the risk of motor vehicle accidents after marijuana impairment is much lower than the risk of intoxicated driving after consuming alcohol.

In fact, the most comprehensive study shows that "culpability" for 3,400 motor vehicle accidents over a ten year period shows that drivers with THC concentrations in the blood of less than 5 ng/mL have a risk of causing an vehicle accident that is no higher than that of driver's with no drugs in their system.

Smoking marijuana rapidly transfers THC into the blood stream. THC can reach the highest concentrations within five to ten minutes after marijuana is inhaled and can typically exceed more than 100 ng/mL. After marijuana is consumed, the THC levels in the blood quickly decrease to between one to four ng/ML within three hours.

For regular users of marijuana, blood serum can contain more than two mg/mL of THC even two days after marijuana is last consumed. Other studies show that even secondhand exposure to marijuana can cause THC to show up in the non-user's system at a rate of several nanograms per milliliter.

How Long Does it Take for the Effects of Marijuana to Wear Off?

Many experts on the topic believe that the psychoactive effects of marijuana wear off completely within three to four hours after marijuana was consumed. The effects diminish to levels unexpected to cause any effect on driving after just two hours.

In many of these cases in which THC is detected in the blood or urine an expert witness can be retained to testify that traces levels of cannabis found in the blood or urine exists despite the fact that the driver was not under the influence of marijuana at the time of the stop or arrest.

The graph below shows the expected rising and decreasing levels of THC and the metabolites THC-COOH and 11-OH-THC for a person who occasionally uses marijuana and then abstains from using marijuana for the next several days. The calculations are shown after the person smokes only one marijuana cigarette that contains 34 mg of THC.

Fighting the DUI Marijuana Prosecution

In many of these Tampa DUI marijuana cases, a "Motion to Dismiss" the entire case can be filed when the only drug suspected is marijuana. Additionally, a "Motion in Limine" can be filed to exclude any mention of the THC finding to the jury because in many of these cases no connection can be made to show the driver was under the effects of marijuana at the time he was driving and stopped for DUI in Tampa, Florida.

In other words, if you smoked marijuana on Thursday, and drove a vehicle on Saturday, the carboxy THC may be present in the urine after the stop but it does nothing to prove that the driver was under the influence of marijuana at the time he was stopped for DUI.

False Positives for Marijuana

Additionally, many legal substances can cause a false positive in a urine test including pain medications such as Excedrin IB, Motrin or Advil or Aleve, over-the-counter supplements such as B2, hempseed oil and riboflavin, and prescription medications such as Marinol or Dronabinol. Even certain medical conditions such as liver disease, diabetes, or a kidney infection can lead to a false positive.

Cannainoid Pharmacokinetics

This chart shows THC blood levels when marijuana is smoked or taken orally. When smoked THC is absorbed rapidly, but when consumed orally there is a delayed onset.

Graph of THC Marijuana Cannabis Levels for DUI in Tampa, Hillsborough County, FL


How does urine test or blood anaylsis or hair test show presence of marijuana / cannabis / pot / weed? - Article published in the Ther Drug Monit, Volume 28, Number 2, April 2006, entitled "Review of Biologic Matrices (Urine, Blood, Hair) as Indicators of Recent or Ongoing Cannabis Use" by Frank Musshoff and Burkhard Madea. This article discusses documented case study of subject testing positive for the presence of carboxy THC for 110 days after periods of monitored abstinence. Also shows evidence of subjects testing positive for marijuana (pot, weed, or cannabis) for 60-100 days after monitored abstinence after chronic use.

Finding a DUID or DUI Marijuana Attorney in Tampa and Hillsborough County, FL

Contact an attorney at the Sammis Law Firm for a DUID or DUI Cannabis case in the greater Tampa Bay area including Tampa and Plant City in Hillsborough County, St. Petersburg and Clearwater in Pinellas County, Bartow and Lakeland in Polk County, Bradenton in Manatee County, Dade City and New Port Richey in Pasco County, FL.

Urine and even blood tests to determine marijuana impairment are often unreliable. Call an experienced DUI defense attorney to find out how you can fight DUI Marijuana cases.

This article was last updated on Wednesda, April 13, 2016.