The methods that police officers use to detect cannabis-impaired driving lack a scientific basis, reported a new editorial published in the Journal of Studies on Alcohol and Drugs.
Increasing legalization of cannabis in the US has generated a need for reliable drug tests. However, while police can assess alcohol-intoxicated drivers via a breathalyzer, no equivalent exists for cannabis.
In an editorial, Prof. William J. McNichol of Rutgers University's Camden School of Law discussed various methods currently used by law enforcement to assess cannabis intoxication.
“The Drug Recognition Expert (DRE) Protocol is very popular among police officers and prosecutors. It is a classic example of “police science”—techniques developed by police officers for use in their police work,” wrote McNichol in his editorial.
“That is to say, it is not science-based at all but is merely a police officer's lay opinion encrusted with some of the trappings but little or none of the substance of science. The DRE Protocol purports to use an array of indicators of impairment, almost none of which bear up under close examination,” he added.
McNichol described some of the methods used by law enforcement to assess intoxication from cannabis. Police officers, for example, attempt to assess muscle tone as an indicator of cannabis use by squeezing the subject's limbs. This, he noted, is not how healthcare professionals assess muscle mass, and is an invalid means of assessment. Other methods for evaluating intoxication, such as assessing pulse and physical coordination, are also deficient, he wrote.
“Other aspects of the DRE Protocol's method of detecting marijuana-based impairment would be amusing if they were not so earnestly offered as based on science. The DRE training materials assert that having an “increased appetite” is an indicator of marijuana-based impairment. Having the munchies, as evidenced by an open bag of potato chips, can apparently be part of the basis of a DRE police officer's “science-based,” expert opinion that a driver is impaired," he wrote.
He noted that the lack of scientific rigor behind the DRE protocol leads to unreliable and almost random results. A study from 1998, for example, showed that the protocol produced either false negative or false positive results 45.5% of the time- similar to a coin toss.
“The solution for this problem is plain to see. We must actually do what, so far, we have only pretended to do. We must develop and adopt a scientifically valid, objective, and reliable method for detection of marijuana-based impairment that can be practically implemented in the field,” he wrote.
Sources: EurekAlert, Journal of Studies on Alcohol and Drugs
