How does law enforcement attempt to prove suspicion of Marijuana DUI?

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If you have been arrested for driving under the influence of marijuana your first course of action should be to contact a criminal defense lawyer in the area of your arrest. It can be difficult to prove that you were under the influence while operating a vehicle. The arresting officer may testify that at the time of your arrest your driving pattern, physical appearance, and your field sobriety test results demonstrated that you were impaired. However, it is impossible for the arresting officer to determine drug levels at the time of your arrest.  Submitting to further testing, such as a blood test, may show that marijuana is in your system but it will not reveal that you were experiencing effects that would impair your ability to drive at the time in question.

When blood tests are used to determine marijuana in the blood stream they cannot provide an accurate time of impairment because THC remains in your system long after the effects of marijuana have worn off. There is no definitive way to prove that you were under the influence of marijuana while operating a vehicle. Marijuana DUI does not use the blood-alcohol concentration (BAC) that is used to determine impairment in alcohol related DUI cases.

With that said, it’s still important to understand that under California law it is unlawful for any person who is under the influence of alcohol or drugs to drive a vehicle.

What evidence is used in proving a marijuana DUI?

Unlike driving under the influence of alcohol a breath test cannot be used to determine the presence of marijuana. The breath test does not register the presence of marijuana or other drugs in the system. It may be requested by the arresting officer that you submit to a blood or urine test instead. In addition to test results, evidence presented by the prosecution may also include comments from the arresting officer testifying to your:

  • Physical appearance
  • Erratic driving
  • Incriminating statements
  • Conduct

The arresting officer may not be qualified or trained to identify drug symptoms. In these cases it may be possible for the defense to prevent the officer from giving an opinion on your impairment. An officer who has the skill to testify on the symptoms of drugs and their resulting impairments may be used. This officer would be known as a DRE, or drug recognition expert.

Refusing questions and tests

If you are stopped by the police on suspicion of driving under the influence of marijuana you have the right to refuse any questions, other than identifying yourself to the officer. You also have the right to refuse any field sobriety tests they may subject you to. Always remain respectful and cooperative with the officer in charge and simply provide a statement that you have been advised of your right to not answer questions. If you refuse to submit to a chemical test, you may lose your driving privilege.

If the officer gives you the opportunity to choose between a breath or blood test, a breath test is preferable because it does not measure THC levels in the blood. However, if the officer feels you may be under the influence of marijuana you may be asked to submit to a blood or urine test. Legally, an officer needs a warrant to obtain a blood sample. However, if you refuse, you may suffer a license suspension.

Marijuana DUI cases are not as easy to prove as alcohol related DUI cases but can still be very intricate and require the representation of an experienced criminal defense lawyer.

If you have any questions regarding the services provided at the Law Office of Gregory W. Fox,
or would like to schedule your free initial consultation, please contact us today at (559) 222-5800. Hablamos español.