How Police Test for Marijuana DUI in California

A lot has changed over the last few years. Although few people are still supporting the notion that Marijuana is extremely dangerous to a person’s health, there are still a number of concerns raised by some about other potential dangers associated with the use of Marijuana, the most credible being allegations that THC impairs a person’s ability to drive.

This has led to attempts by lawmakers and authorities to find ways to detect Marijuana impairment now more than ever. Unlike Alcohol and other drugs, blood and urine tests can detect Marijuana in a person’s blood stream several weeks after the drug has been consumed, making it especially difficult for a method of detection that proves a person consumed forms of THC within hours of driving.

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So how do authorities test for THC impairment by drivers in California? They start with a field sobriety test. If you fail, that gives them probable cause to arrest you.

Marijuana Field Sobriety Test

If a California officer pulls you over and believes that you are driving under the influence of Marijuana, their first course of action to verify their suspicions will usually be a field sobriety test.

A field sobriety test is a series of physical and mental exercises administered by police during Marijuana DUI investigations to help determine a driver’s level of impairment. California law enforcement officials rely heavily on field sobriety tests when deciding whether or not to arrest a person who is suspected of driving under the influence.

There are different types of field sobriety tests used by California officers, the three “standardized” tests being the “horizontal gaze nystagmus test”, the “walk and turn test”, and the “one-leg stand”, all of which are detailed below.

Horizontal Gaze Nystagmus Test

  • The horizontal gaze nystagmus test is usually administered by an officer moving an object, or their own finger, from side to side in front of a person’s face. The reason they do this is to try and detect an involuntary jerking of the eye associated with high levels of intoxication. A person’s eye will reportedly jerk naturally after being strained beyond a 45 degree angle, but if the eye begins to jerk at or before moving 45 degrees, CA police officers can reference this reaction as evidence that a driver is under the influence.
  • The National Highway Traffic and Safety Administration (NHTSA) estimates that these tests are 77% reliable.

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Walk and Turn Test

  • The walk and turn test splits a suspected Marijuana DUI offender’s attention between physical and mental tasks. Also referred to as the “walk the line test”, the officer provides instructions to the suspected offender and watches to see if any of the following occur:
    • Loss of balance
    • Wrong number of steps
    • Inability to stay on the line
    • Breaks in walking
    • Beginning before instructed
  • NHTSA estimates that this test is effective 68% of the time.

One Leg Stand Test

  • Another divided attention test, during the “one leg stand” an officer will instruct the suspect to raise his or her foot, hold still, count, and look down. An officer may arrest the suspect if any of the following behaviors are observed:
    • Swaying
    • Hopping
    • Putting foot down
  • NHTSA estimates that this test is effective 65% of the time.

Blood, Breath, or Urine Test

In California, if an officer has probable cause to believe that you were driving under the influence of Marijuana or any other drug, you have already given your consent to provide a blood, breath, or urine test.

A urine test is not common, but if officers are unable to administer a blood or breath test, you are required to take a urine test. For Marijuana, using blood, breath, or urine tests to determine whether a person is under the influence of THC at the time they were driving is a flawed system, as blood and urine tests are unable to determine whether Marijuana was consumed within the last few hours while breath testing technology does not have the ability to detect Marijuana, as of now.

Saliva Drug Swab Test

Due to the increased number of drivers driving while under the influence of drugs, police officers in Los Angeles are now testing using drug swabs at DUI checkpoints. The test is roughly eight minutes long and uses a person’s saliva to detect THC, crystal meth, methadone, cocaine, and several other prescription medications.

There are conflicting reports as to the accuracy of these tests. The tests work by detecting trace amounts of drugs in California driver’s saliva, but there can be traces of some drugs in your saliva up to three days after consuming them. This leaves plenty of room for doubt in a court room, as it would be nearly impossible to prove without a shadow of a doubt in a court room that a person was under the influence of Marijuana at the time they were driving solely based on a saliva drug swab.

California Marijuana DUI Defense

If you or your loved one were arrested and charged with driving under the influence of Marijuana in California, you may have several options to help defend your innocence. Contact one of our Marijuana DUI defense attorneys today. Having had successful Marijuana DUI case outcomes for the majority of those I have represented, our firm has the experience and history of success that will help you to feel confident about your case moving forward.

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Call (888) 250-2865 today to receive a free case evaluation from one of our skilled Marijuana DUI defense lawyers.