I’ve written here in past posts about the difficulties of trying to use a breathalyzer on a driver to determine whether he is under the influence of marijuana. See Is It Possible to Prove Driving Under the Influence of Drugs?. As a study authored by Dr. Jim Hedlund, formerly a senior official with the National Highway Traffic Safety Administration, has concluded:.
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;
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).
In addition, 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). GAO (2015) agrees: “identifying 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.”
Will science and profit-hungry corporations ever be able to produce a breath-analyzing device that can accurately and reliably measure the amount of marijuana in a a driver’s blood? Doubtful, but not for lack of trying. The following is from a recent edition of Forensic magazine:
“At the same time that marijuana use is growing dramatically, law enforcement has been impeded by the lack of tools to help identify stoned drivers and get them off the road,” according to the company Hound Labs.
Now, the company is claiming they’ve created a technology capable of detecting THC (tetrahydrocannabinol) levels below 500 pg in a breathalyzer test. According U.S. News & World Report, the technology will be tested early next year in clinical trials.
“Measuring marijuana is not a simple extension of the technology in current alcohol breathalyzers,” according to Hound Labs. “The approach used in an alcohol breathalyzer won’t detect THC molecules in lungs because THC requires a scientific method more than a million times more sensitive than one needed to measure alcohol. Until now, very large, expensive and specialized detection tools were needed to detect THC in breath.”
The company’s CEO Mike Lynn said the law enforcement version of the product will sell for “well under a thousand dollars,” and the commercial consumer version will be even less, reports the U.S. News & World Report.
If true, this would be quite a break-though. If true….