Why Marijuana DUI is Hard to Scientifically Prove

Why Marijuana DUI is Hard to Scientifically Prove

Unless you are not driving with the caution characteristic of a sober person in California, a San Diego DUI – Marijuana charge should not be pursued. Marijuana driving is fine as long as your driving is fine.

Scientific Reasons why marijuana can not be relied on in a San Diego California DUI prosecution begin with sound conclusions drawn by a former senior official with the National Highway Traffic Safety Administration, Dr. Jim Hedlund:

“The relations between a drug’s presence in the body, its concentration, measured in blood, breath, saliva or urine, and its impairing effects are complex and not understood well. A drug may be present at low levels without any impairing effects. Some drugs or metabolites may remain in the body for days or weeks, long after any impairment has disappeared (Berning et al., 2015; U.S. Government Accountability Office, 2015).

In particular, marijuana metabolites can be detected in the body for weeks after use (Berning and Smither, 2014).  On the other hand, concentrations in the body of some drugs decrease rapidly while impairing effects persist. For marijuana, THC concentrations fall to about 60% of their peak within 15 minutes after the end of smoking and to about 20% of their peak 30 minutes after the end of smoking while impairment lasts for 2 to 4 hours (Kelly-Baker, 2014; Logan, 2014).

Individuals differ in how their bodies absorb and metabolize a drug. In experimental settings, wide ranges of drug concentrations produce similar levels of impairment in different individuals (Berning et al., 2015).”

NHTSA’s observation is generally accepted: “At the current time, specific drug concentration levels cannot be reliably equated with a specific degree of driver impairment” (Berning et al., 2015).”

NHTSA in a July 2017 to their “Marijuana-impaired driving, a report to Congress” says:

“While the presence of THC in a driver (blood, oral fluid, etc.) does not establish impairment, it also does not distinguish been active use of marijuana and environmental exposure or contamination. Some studies have shown that people exposed to second-hand marijuana smoke can test positive for THC (Cone, et al, 2015; Moore et al, 2006).”

Our United States Government Accountability Office agrees:

“[I]dentifying a link between impairment and drug concentrations in the body, similar to the 0.08 BAC threshold established for alcohol, is complex and, according to officials from the Society of Forensic Toxicologists, possibly infeasible.” [“DRUG-IMPAIRED DRIVING – Additional Support Needed for Public Awareness Initiatives,” GAO, February 2015, page 16]

What about the newer roadside marijuana tests?  A roadside marijuana test tests for the inactive metabolite of marijuana, which can remain in one’s blood stream for hours, days, or weeks.  It is not active, so in many instances, the “marijuana high” could, and most likely did, pass…maybe days ago. Marijuana is not like alcohol.  Marijuana affects people differently and impairment could only be judged clinically, certainly not by a roadside test.  If someone has not smoked in days, but has THC in her or his blood, it will not register.  So it would be scientifically impractical to correlate THC to impairment that is not in the blood (from recent smoking).

Why Marijuana DUI is Hard to Scientifically Prove


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