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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.

Unlike alcohol, marijuana does not act as a general central nervous system depressant, impairing functions throughout the body. Nevertheless, the main psychoactive substance in marijuana, tetrahydrocannibol (THC), is known to have an impact on several functions of the brain.

The impact on brain function can sometimes impact the ability to drive safely and divide one's attention when focusing on several things at the same time such as balance, processing information, and following instructions. Some research has shown that the consumption of marijuana can impair the ability to drive, although other studies show very little impact on safe driving when a suspect has recently consumed marijuana.

Traditional field sobriety exercises are not accurate or reliable when it comes to documenting impairment from marijuana. Even the government's own research on marijuana caused NHTSA to conclude: "It is difficult to establish a relationship between a person's THC blood or plasma concentration and performance impairing effects. … It is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH concentrations.”

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.

Although both blood and urine tests can detect cannabinoids (THC and the metabolites of TCH), the results of these tests do very little to predict actual impairment at the time of driving. In Florida, the result of the blood test will typically show results for the following:

  • Delta-9-tetrahydrocannabinol (THC) measured in ng/ML of bloood - the most prevalent compound of cannabis sativa and produces most of the characteristic pharmacological effects of smoked marijuana;
  • 11-OH-delta-9-tetrahydrocannabinol measured in ng/ML; and
  • 11-Nor-9-carboxy-delta-9-tetrahydrocannabinol measured in ng/ML of blood - often referred to as 11-Nor-9-carboxy-Δ?-tetrahydrocannabinol, 11-nor-9-carboxy-THC or THC-11-oic acid. This result indicates the presence of the main secondary and inactive metabolite of tetrahydrocannabinol, which is formed in the body after cannabis is consumed.

DUID \ DUI Marijuana Attorneys in Tampa, FL

The blood or urine tests performed in Florida are very BAD at showing whether a driver is impaired by marijuana 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.

Call 813-250-0500 to find out more about how we fight these difficult cases with the goal of getting the charges dropped completely.


Urine and Blood Tests with 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.

If the arresting officer obtains a blood or urine sample in these cases, the FDLE Laboratory Report will show a result of "11-Nor-9-carboxy-delta-9-tetrahydrocannabinol" only which means although the person smoke marijuana in the past, it was NOT consumed within the 8 hour period before driving.

As a result, the attorney will file a motion in limine to exclude any mention of this test result since it is irrelevant to the issue of actual impairment at the time of driving and is unduly prejudical since it shows someone used marijuana in the past.

Even the government's own studies show that it is very difficult to accurately determine from a blood test for the presence of either THC and/or carboxy-THC in blood in a single sample either of the following:

  • impairment from marijuana; or
  • even the last time marijuana was ingested.

According to page 107 of a recent NHTSA study on "Marijuana and Actual Driving Performance":

"One of the program's objectives was to determine whether it is possible to predict driving impairment by plasma concentrations of THC and/or its metabolite, THC-COOH, in single samples. The answer is very clear: it is not. Plasma of drivers showing substantial impairment in these studies contained both high and low THC concentrations; and, drivers with high plasma concentrations showed substantial, but also no impairment, and even some improvement."

Other publications recognize that retrograde or back-extrapolation is not an option due to the complex pharmacokinetic profile of THC. See Wille et al: Conventional and alternative matrices for driving under the influence of cannabis: Recent progress and remaining challenges at page 801.


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 and insufficient evidence shows impairment from 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.

The motion to dismiss or the motion in limine can also ask to exclude any evidence of finding THC or its metabolites in the blood or urine test.

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.

False positives are expected to increase as law enforcement officers to breath testing in DUI marijuana cases.


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.


Problems with Marijuana and Field Sobriety Testing

In several recent cases, the courts have started throwing out any evidence of field sobriety exercises when the defendant is suspected only of marijuana use.

In a recent Massachusetts Supreme Judicial Court ruling, the Defendant was charged with operation of motor vehicle while under influence of marijuana. The criminal defense attorney for the defendant filed a motion for a Daubert-Lanigan hearing seeking to challenge the admissibility of evidence concerning his performance on field sobriety tests (FSTs) conducted after the stop.

The Supreme Judicial Court eventually held that:

    • jurors could use their common sense in evaluating whether the defendant was impaired due to marijuana use;
    • lay officer testifying to defendant's performance on FSTs that measured balance and coordination did not have to be qualified as an expert;
    • the lack of consensus in the scientific community as to whether FSTs used to measure alcohol impairment also measure impairment from marijuana use did not necessitate exclusion of results of such tests; and
    • lay officer could not offer an opinion as to defendant's sobriety or intoxication.

Commonwealth v. Gerhardt, SJC-11967, 2017 WL 4127666 (Mass. Sept. 19, 2017).


Jury Instruction for DUI Marijuana Cases with Field Sobriety Exercises

The Gerhardt court also found that another consequence of the lack of consensus regarding the FSTs is the fact that FSTs cannot be treated as scientific “tests” of impairment and the evidence of performance on FSTs, alone, is not sufficient to support a finding that a defendant's ability to drive safely was impaired due to the consumption of marijuana. The court developed the following model jury instructions for DUI cases involving the use of marijuana:

You heard testimony in this case that the defendant, at the request of a police officer, performed or attempted to perform various roadside assessments, such as [Here outline the nature of the evidence, e.g., walking a straight line, balancing on one foot]. These roadside assessments are not scientific tests of impairment by marijuana use. A person may have difficulty performing these tasks for many reasons unrelated to the consumption of marijuana.

It is for you to decide if the defendant's performance on these roadside assessments indicate that his [her] ability to operate a motor vehicle safely was impaired. You may consider this evidence solely as it relates to the defendant's balance, coordination, mental clarity, ability to retain and follow directions, ability to perform tasks requiring divided attention, and other skills you may find are relevant to the safe operation of a motor vehicle.

It is for you to determine how much, if any, weight to give the roadside assessments. In making your determination, you may consider what the officer asked the defendant to do, the circumstances under which they were given and performed, and all of the other evidence in this case.

Finally, evidence of how a defendant performed in roadside assessments, standing alone, is never enough to convict a defendant of operating under the influence of marijuana.

Many criminal defense attorneys in Florida are filing motions to exclude or limit the types of testimony officers can give about field sobriety exercises in a case involving the consumption of marijuana.


Finding a DUI Marijuana Lawyer in 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.

We understand the complex issues raised in these cases, especially for field sobriety exercises and the results of a urine or blood test. We know how to show that urine and blood testing are unreliable when trying to determine what impairment occurred because someone smoked week before driving.

Call an experienced DUI defense attorney to find out how you can fight DUI Marijuana cases.


This article was last updated on Monday, February 12, 2018.