this post was submitted on 30 Jun 2025
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For years now, U.S. police departments have employed officers who are trained to be experts in detecting "drugged driving." The problem is, however, that the methods those officers use are not based on science, according to a new editorial in the Journal of Studies on Alcohol and Drugs (JSAD).

With marijuana now legal in many U.S. states, the need for reliable tests for marijuana impairment is more pressing than ever. Police can evaluate alcohol-intoxicated drivers by using an objective measure of breath alcohol results. But there is no "breathalyzer" equivalent for marijuana. The drug is metabolized differently from alcohol, and a person's blood levels of THC (the main intoxicating chemical in marijuana) do not correlate with impairment.

So law enforcement relies on subjective tactics—roadside tests and additional evaluations by police officers specially trained to be so-called drug recognition experts (DREs). These officers follow a standardized protocol that is said to detect drug impairment and is said to even determine the specific drug type, including marijuana.

The process involves numerous steps, including tests of physical coordination; checking the driver's blood pressure and pulse; squeezing the driver's limbs to determine if the muscle tone is "normal" or not; and examining pupil size and eye movements.

But while the protocol has the trappings of a scientific approach, it is not actually based on evidence that it works, said perspective author William J. McNichol, J.D., an adjunct professor at Rutgers University Camden School of Law.

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[–] Thistlewick@lemmynsfw.com 92 points 5 days ago (1 children)

The process involves numerous steps, including tests of physical coordination; checking the driver's blood pressure and pulse; squeezing the driver's limbs to determine if the muscle tone is "normal" or not; and examining pupil size and eye movements.

Steps not mentioned:

  • is the suspect Black?
  • does the suspect fail to defer to you as an infallible authority?
  • have you hit your quota of arrests/citations today?
[–] Grimy@lemmy.world 18 points 4 days ago* (last edited 4 days ago)
  • are you in a bad mood? Do you need to vent?
[–] ArcaneSlime@lemmy.dbzer0.com 55 points 4 days ago (1 children)

squeezing the driver's limbs to determine if the muscle tone is "normal" or not;

So basically if the cop decides I'm a weak pussy who skipped arm day, I'm high? Fucking WAT? This isn't even pseudoscience it's just flinging shit at a wall and seeing what sticks lmao, that's dumb.

[–] RebekahWSD@lemmy.world 14 points 4 days ago

Oh cool this will target disabled people real well! My twin had like 10 percent average strength in their arms, so guess they're just screwed!

[–] Ushmel@lemmy.world 44 points 5 days ago (2 children)

Police work is all pseudoscience. And they always get a pass bc they're cops.

[–] interrobang@lemmy.blahaj.zone 6 points 4 days ago

100%, look no further than 'excited delirium' smdh

[–] CAWright@infosec.pub 2 points 4 days ago

Very true. Pretty much everything is made up from something they saw on CSI or NCIS the night before. They are trying hard to make their "industry" cerebral when it just isn't.

[–] Kyrgizion@lemmy.world 25 points 5 days ago* (last edited 5 days ago)

Well, yeah. They're only meant as a probable cause machine, not to actually make things safer for anyone. Same as drug dogs basically.

[–] kowcop@aussie.zone 18 points 5 days ago (2 children)

As someone who is in a country without marijuana legalisation, what is wrong with the current laws? Is there a massive spike in deaths where the cause was attributed to marijuana use?

When we keep having these arguments about how our country could possibly legalise given our driving laws, I always point to the tonnes of countries that have already legalised and ask why we need to reinvent the wheel.

[–] MalReynolds@slrpnk.net 7 points 4 days ago (1 children)

Well, it's legal for medical purposes, and the current aussie protocol, AFAIK, is got THC in your system (cheek swab), you lose (and a blood test I think, happy for someone knowledgeable to jump in). Cancer chemo, no (legal) driving for you... This crap would be a step up.

[–] prole@lemmy.blahaj.zone 3 points 4 days ago

Wow that's fucking stupid.

[–] I_Has_A_Hat@lemmy.world 5 points 4 days ago

Oh, see, you're under the impression that this is about public safety. It's not. It's about giving insurance companies an excuse to deny claims.

[–] Tehdastehdas@piefed.social 4 points 3 days ago

You can detect impaired driving by observing the car in traffic.

[–] explodicle@sh.itjust.works 10 points 4 days ago

My eyes have been red ever since I got LASIK. 😵‍💫

[–] Etterra@discuss.online 3 points 4 days ago

This is hardly the least scientific anything cops do.

[–] queermunist@lemmy.ml 5 points 4 days ago
[–] Maalus@lemmy.world 4 points 4 days ago

A brethylizer test for alcohol isn't "objective" either and all it does is create cause to test your blood.

[–] Korhaka@sopuli.xyz 3 points 4 days ago (3 children)

But there is no “breathalyzer” equivalent for marijuana.

What do the mouth swabs test for then?

[–] JoeBigelow@lemmy.ca 12 points 4 days ago

Metabolites I imagine, which can persist long after intoxication. They are illegal to be used in Maine

[–] prole@lemmy.blahaj.zone 2 points 4 days ago

They don't measure whether or not you are currently under the influence, and even then, I think they're relatively easy to game.

[–] Passerby6497@lemmy.world 1 points 4 days ago

What do the mouth swabs test for then?

An excuse to arrest you