The drugalyser

Colour me sceptical:

It hopes the so-called “drugalyser” will make it easier to catch and prosecute offenders and help reduce accidents. The drug testers will be able to screen for an array of illegal substances, including cocaine and ecstasy.

A positive result would mean that police would no longer have to wait for permission from a doctor before a blood test could be taken to be used as evidence in court.

No, not about the desirability of such a test. People spaced out on drugs are as bad as those drunk, dangerous to other road users and thus righteously to be prosecuted.

No, rather, it\’s the technology that worries. Here\’s the detection times that such oral based testing has:

Detection in saliva tests begins almost immediately upon use of the following substances, and lasts for approximately the following times:

NOTE: Saliva tests are highly sensitive and detection times can vary considerably based on the cutoffs used.

So, the presence of such drugs, or their metabolytes, in such a sample does not in fact show being under the influence of said drugs. For someone is not driving (or any other way) impaired two days after taking smack, nor several days after taking meth etc.

And yes, poppy seed pastries can indeed give a false positive for opiates.

The test are good for checking whether someone has been taking drugs. They\’re not good for checking whether someone was actually under their influence at the time of driving.

4 thoughts on “The drugalyser”

  1. Brian, follower of Deornoth

    “The test are good for checking whether someone has been taking drugs. ”

    We’d need to know a lot more about the false positive rate before we can accept that.

  2. More to the point, false positives for impairment. Given that (as someone said here but I can’t remember who) in the New Labour era the process is the punishment, it’s only “reasonable suspicion” that restrains the filth from holding you all day in a cell and annulling your visa-free travel to the US.

    Is failing this test reasonable suspicion of impairment? I’d say there was almost no correlation on the data above.

  3. This is just another way to avoid doing any of the hard stuff, all that ‘in my judgement’ and ‘gathering evidence’ stuff, isn’t it?

    You’d think the police would just use video evidence to show obvious impairment at trial.

    Except, of course, as we all know today, the impairment it shows is often their own…

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