DUI and Drugs in Florida: Drug Kinetics


Driving under the influence (DUI) or drug dui is a serious offense that can have life-altering consequences. In Florida, as in many other states, DUI laws also apply to the use of drugs, including cannabis. This article explores the complex relationship between THC (the psychoactive component in cannabis) and DUI in Florida, shedding light on the scientific aspects and legal implications associated with drug-related DUI cases.

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Driving under the influence (DUI) is a serious offense that can have life-altering consequences. In Florida, as in many other states, DUI laws also apply to the use of drugs, including cannabis.
“understanding the intricate relationship between THC kinetics and DUI in Florida is essential for both legal professionals and medical experts. “

THC and the Brain

One crucial aspect of understanding drug DUI in Florida is comprehending the effects of THC on a driver’s brain. THC Kinetics and the concept of Hysteresis play a significant role in this context. THC Kinetics refers to the study of how THC is processed in the body, while Hysteresis describes the temporal lag between the concentration of THC in the blood and its effects on the brain.

In a seminar led by Dr. Stefan Rose of University Medical & Forensic Consultants, Inc., it was emphasized that the blood and brain THC concentrations are often in disequilibrium, characterized by “counterclockwise hysteresis.” This means that when blood THC levels are high, intoxication is low, and vice versa. This dynamic makes it impossible to predict a person’s impairment solely based on a blood THC test result. Nonetheless, there are severe penalties for refusing to take a test when requested.


Urine Testing and Impairment Prediction

The scientific basis for urine testing and its ability to predict impairment by a driver is another important aspect to consider in drug DUI cases. The National Highway Traffic Safety Administration (NHTSA) addresses Urine THC Kinetics in their Drugs and Human Performance Study. Detecting total THC metabolites in urine, primarily THC-COOH-glucuronide, indicates prior THC exposure but does not correlate with the window of intoxication and impairment.

Controlled clinical studies provide some insights into urine cannabinoid concentrations. While they can be used as a reference, these data are typically reflective of occasional marijuana use rather than chronic exposure. The detection window in urine can vary, but positive test results generally indicate use within 1-3 days, with potential for a longer detection window for chronic users.

THC Kinetics and Drug Driving

Understanding the kinetics of THC in the body is essential for assessing its impact on drug driving:

  1. THC is rapidly absorbed into the bloodstream when smoking marijuana.
  2. The peak blood THC concentration occurs shortly after smoking.
  3. The concentration of THC in the brain lags behind the blood concentration, creating hysteresis.
  4. There is no direct correlation between blood THC concentration and intoxication.
  5. Organs with high blood flow, such as the brain, liver, kidneys, and lungs, accumulate THC more quickly.
  6. Fat tissue slowly accumulates and releases THC over extended periods, especially in chronic users.
  7. Residual THC levels can be present in the blood for days or even weeks after use.
  8. A single blood THC result cannot determine the timing or amount of marijuana consumption.
  9. Clinical correlation is necessary to assess impairment.

Can THC Results Predict Impairment in DUI and Drug Prosecutions?

Predicting impairment based on THC results is challenging due to various factors:

  1. THC Blood: Serum ratio remains unknown (if the sample is serum).
  2. The THC Kinetic curve is not well understood.
  3. The hysteresis effect of THC is not fully known.
  4. The presence of residual THC in blood is uncertain.
  5. The drug-dose response for THC is unclear.
  6. Tolerance to THC varies among individuals.
  7. The impact of CBD remains uncertain.
  8. Neurologic exams for THC effects are not always conducted.
  9. Even NHTSA acknowledges the difficulty in predicting impairment based on THC levels.

Challenging Blood Drug Results

For DUI attorneys and experts, challenging blood drug test results is critical:

  1. Challenge the chemical analysis for quantitative and qualitative accuracy, as quantitative values always have associated errors.
  2. Acknowledge that a single blood drug test cannot predict blood drug concentration at the time of a stop or crash.
  3. Blood drug concentrations are constantly changing, making them unpredictable.
  4. A blood drug concentration cannot predict an individual’s pharmacologic effect or impairment.
  5. The wide range of responses to drugs within populations makes individual predictions difficult.

Cross-Examination Questions

During drug DUI cases, asking the right questions is crucial:

  1. Determine the type of sample analyzed (whole blood, serum, or plasma).
  2. If serum/plasma, inquire about the whole blood: serum THC ratio.
  3. Seek clarification on the sample type used in pharmacokinetics/pharmacodynamics studies.
  4. Ask if necessary corrections were made if the sample type differed.
  5. Investigate how the defendant’s blood: serum THC ratio was determined.
  6. Highlight that the brain is the target organ affected by THC.
  7. Challenge the lack of a specific threshold for brain THC concentration causing impairment.
  8. Emphasize the absence of a direct correlation between blood THC and brain THC.
  9. Point out the absence of published correlations between blood THC, brain THC, and impairment.

Consultation on DUI and Drugs

For legal professionals seeking a forensic consultation in their drug DUI cases, contacting Dr. Stefan Rose directly is recommended. His expertise can provide valuable insights and assistance in navigating the complex world of drug-related DUI cases.

In conclusion, understanding the intricate relationship between THC kinetics and DUI in Florida is essential for both legal professionals and medical experts. These insights can help individuals make informed decisions and challenges related to drug DUI cases, ensuring a fair and just legal process.

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