Police test marijuana barrier ‘pseudoscience’

Police across the United States are using roadside tests to detect “cannabis driving that doesn’t go as much as coins,” according to a scathing analysis published in the Journal of Alcohol and Drug Research.

The editorial argues that the approach adopted by thousands of trained officials relies on pseudoscience rather than proven science and technology, causing serious legal and public safety issues.

With marijuana now legal in many states, the need for reliable damage testing has become urgent. Unlike alcohol that can be measured objectively with a breath analyzer, marijuana presents unique challenges that allow law enforcement to rely on subjective assessment methods that lack a scientific basis.

“The evidence available shows that they are not better than coin tossing,” said William J. McNichol, an adjunct professor at Rutgers University’s Camden Law School and author of the Perspective article.

Drug identification expert question

The centre of the dispute is Drug Identification Experts (DRES) – more than 8,000 police officers across the country follow a standardized protocol that claims to detect drug barriers and identify specific substances. The process involves multiple steps, including coordinated testing, blood pressure checks, pulse measurements, and checking students’ size and eye movements.

However, McNichol believes that this approach represents “police science,” a technology developed by police work rather than evidence-based approaches. The protocol includes suspicious metrics such as squeezing the limbs of the drive to assess “muscle tone” and diagnosing psychotic conditions such as curb paranoids.

Key details not highlighted in the press release: 1998 controlled laboratory study found that the DRE protocol produced false negative or false positive results 45.5% of the time. What is even more disturbing is that when both groups of DREs evaluated the same subject, they only agreed to marijuana barriers 69% of the time.

Science Challenges

The basic problem stems from attempting to apply alcohol testing methods to marijuana without taking into account the key differences between these substances:

• Alcohol is water-soluble; cannabinoids are fat-soluble and metabolic.
• Blood level has nothing to do with damage level
• Heavy-duty users develop tolerance, complicating standardized testing
• Multiple cannabinoids affect damage, not just THC
• Some cannabinoids last long after the damage is over

Legal and social consequences

The bet goes far beyond academic debate. DUI convictions are subject to severe penalties, including revocation of permits, unemployment and a lasting criminal record. McNichol warned that relying on “the evidence of distrust destroys the credibility of the law” and “contains the seeds of its own destruction.”

Several courts have begun excluding DRE testimony, with Maryland, Michigan and Rhode Island rejecting it altogether. New Jersey allows DRES to testify only that this behavior is “consistent” with marijuana use, while Minnesota prohibits officials from calling themselves “experts.”

This problem has gone beyond roadside testing. Despite the same scientific limitations, workplace damage identification experts (wires) now adopt a similar approach in employment settings.

The way forward

Experts stress the urgent need for scientifically validated alternatives. “Developing more robust tools to identify drivers of marijuana barriers in an impartial manner is crucial to ensuring the safety of the road,” wrote Thomas D. Marcotte and Robert L. Fitzgerald of the UC San Diego Cannabis Research Center at UC San Diego.

McNichol advocates for the rigorously validated new psychomotor tests and biochemical markers, and the known error rate is transparent to courts and juries. Crucially, he believes that leadership in setting these standards must be moved from law enforcement to the scientific community.

McNichol notes that funding for such research already exists through cannabis tax revenue. “The money is there, if it can only be allocated correctly,” he said. Instead of supporting current DRE programs, the funds could fund the powerful scientific research needed to develop truly reliable methods for damage detection.

As marijuana legalization continues to expand, pressure has increased to replace pseudoscientific police technology with evidence-based approaches to protecting public safety and individual rights.

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