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Roadside Marijuana Screening Tests

Roadside Marijuana Screening Tests

Legalization of Marijuana Creates New Challenges

 The passage of Proposition 64 by the voters of California in November of 2016 approved the use and cultivation of recreational marijuana in California.  Washington and Colorado had previously done so and set per se limits for the amount of THC permitted to be in the blood of a driver at 5 nanograms.  The California Legislature has considered setting specific limits but has yet to do so.   Scientific studies that have been conducted using sophisticated driving simulators suggest that THC levels of 8.2 nanograms was equal to a blood alcohol concentration of 0.05% and a THC level of 13.1 nanograms was equal to a blood alcohol level of 0.08%.  These studies also show that THC combined with alcohol has a potentiating effect and the combination will enhance impairment.


But the scientific truth is that specific levels of THC do not have a direct relationship to levels of impairment in the same way that alcohol does. THC is stored in fat cells and can be detected weeks later, especially in regular users.  THC is absorbed and eliminated in different ways than alcohol and is less predictable and as a result, it is impossible to extrapolate what a THC level was at the time of driving from a chemical test of blood or urine taken later.


Because of the unreliability of chemical testing for THC as a predictor of impairment, prosecutors rely on police officer testimony about driving patterns that may suggest impairment and observational evidence such as performance on field sobriety tests and their subjective interpretation symptoms of impairment.  The prosecution’s case is much weaker if the arresting officer merely performed standard field sobriety tests and did not call upon a trained Drug Recognition Expert  to perform a Drug Recognition Examination.





Law enforcement has been utilizing roadside breath testing devices as screening tests for alcohol for decades.  These fuel cell devices provide probable cause for arrest and in some jurisdictions may be used as evidential tests.  In California, their use is authorized by statute.


It is now possible to conduct on the spot drug testing to determine if a driver has marijuana in their system.  The Draeger Drug Test 5000 is a salvia test that requires the subject to swab their mouth with a cotton swab.  The swab is then placed into the device along with a vial with a reagent and a preliminary qualitative analysis is preformed.  A positive will result in an arrest and a subsequent blood test for a quantitative level.  A negative may still result in an arrest if the officer observes symptoms consistent with impairment since the Draeger is only sensitive to seven types of drugs.

California law enforcement has conducted roadside studies of the Draeger Saliva Drug Test 5000 including a partnership between the Orange County District Attorney’s Office, The Fullerton Police Department and The Orange County Crime Lab which involved the voluntary participation of drivers between 2013 and 2014 and found that the device was effective for cocaine and amphetamines but provided many false positives and false negatives for both marijuana and prescription medication.  A bill that was presented to the legislature to provide for roadside drug swabbing failed in the last session.









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By Barry T. Simons: “It is my honor and privilege to fight for my clients; challenge unjust laws; protect our Constitution and to be a thorn on the side of injustice”.

By Barry T. Simons: “It is my honor and privilege to fight for my clients; challenge unjust laws; protect our Constitution and to be a thorn on the side of injustice”.