How Do Police Prove Impairment With DUI Marijuana Cases?

California law renders it illegal to drive while under the influence of alcohol or drugs. Proving that a driver is guilty of driving under the influence of marijuana (DUI-marijuana) is more complex than proving DUI-alcohol. There is no “per se” amount of marijuana a person has to smoke or ingest in order to be unlawfully under the influence. Instead, police and prosecutors must demonstrate that a driver’s mental or physical abilities were impaired by marijuana or another drug while driving. Police and prosecutors can use a variety of evidence and methods to show impairment. Continue reading to learn how the government may try to prove DUI-marijuana, and call a seasoned California criminal defense lawyer if you are facing DUI charges in California.

Evidence of Impairment

When a police officer pulls a driver over for any driving infraction or on suspicion of DUI, they will look for a variety of evidence to indicate that a driver may be intoxicated. Evidence that may support an arrest on suspicion of DUI includes:

  • The defendant’s driving
  • The defendant’s statements to the police officer
  • The defendant’s performance on field sobriety tests (walking a straight line, standing on one leg, tilting their head back and counting to 30, etc.)
  • Physical indicators of intoxication, including:
    • Dilated pupils
    • Speech patterns
    • Smell of marijuana
    • Rapid heart rate
    • Rapid breathing
    • Red eyes
    • Slowed reaction time

The police may testify to any or all of the above at trial to prove the defendant was driving while under the influence of marijuana. The government may also present evidence that the defendant was addicted to marijuana to support an inference that they were driving while impaired.

Chemical Testing

Drivers arrested for suspicion of DUI may be asked to submit to chemical testing. If a driver is arrested for suspected marijuana intoxication while driving (based on the indicators discussed above), they will generally not be given the option to choose either blood or breath testing. The driver will be asked to submit to a blood test. The blood test will be used to establish the level of THC in the defendant’s blood. A high concentration will be used as evidence of the driver’s impairment.

Unlike a breathalyzer, the results of a blood test will not be immediately available. Typically, the results will be provided to the defendant at their arraignment as part of an initial discovery packet.

Chemical tests are neither necessary nor sufficient to prove that a driver was impaired by marijuana–they are just additional evidence for the prosecutor. A driver can be convicted of DUI-marijuana even if they were never offered a blood test or if they refused to take a blood test.

Drug Recognition Experts

Typically, the testimony in support of a defendant’s intoxication will come primarily from the arresting officers. However, some jurisdictions employ “drug recognition experts” (DREs) to help with investigations. The arresting officer may call a DRE to examine the defendant after a DUI-marijuana arrest. The DRE will examine the defendant and then may testify at trial about the defendant’s symptoms of impairment.

Get Help from a Compassionate California Criminal Defense Lawyer

If you are facing DUI or other criminal charges in Los Angeles or Southern California, call McReynolds Vardanyan, LLP, in Glendale at 818-855-2115. Our California DUI defense attorneys will fight for your rights and your freedom throughout every step of your case.

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