22 votes

Colorado passes first law in the US to ban arrests based solely on colorimetric drug tests

Posted by skybrian
Tags: politics.usa, usa.co, law, testing.drug, chemistry, studies, false positives, arrests, bans, government.local, justice.criminal, author.holly yan, source.cnn
https://www.cnn.com/2026/04/05/us/colorado-field-drug-test-law

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Title
These common drug tests lead to tens of thousands of wrongful arrests a year, experts say. One state is fighting back | CNN
Published
Apr 5 2026

4 comments

  1. patience_limited
    Link
    Long ago, I worked in an environmental analytical lab. To participate in EPA certification, we regularly got blind samples (no labeling indicating it was a certification test) sent through which...

    Long ago, I worked in an environmental analytical lab. To participate in EPA certification, we regularly got blind samples (no labeling indicating it was a certification test) sent through which we had to chemically identify accurately 100% of the time, and achieve at least 95% accurate quantitative results. [I found this out the hard way because I didn't let a refrigerated sample fully equilibrate at room temperature, and it threw off the quantitative measurement on a colorimetric test, causing a probation on the EPA cert...]

    The spot colorimetric tests described are basically crap - they're not specific, the presence/absence detection is subjective. It's the nature of chemistry that factors like temperature, substance mix or medium (liquid, solid, powder, etc.), quantity tested, all impact the results. Even the manufacturers admitted the tests aren't evidential.

    Even when the "evidence" gets to a secondary analysis, police laboratories are regulated at the state level, if at all. The number of forensic lab scandals suggests there's little or no process for external validation of analytical quality.

    Yes, illicit drug abuse and trafficking has a high social cost. It's worth investigating in the context of potential impaired driving or other crimes meeting the probable cause search standard. But I can't see that it's worth the magnitude of injustice and social harm that flawed testing can cause.

    17 votes
  2. [3]
    skybrian
    Link
    From the article:

    From the article:

    Colorado just enacted the nation’s first law banning arrests based solely on the results of colorimetric drug tests – a field test widely used by law enforcement across the country.

    The tests are popular because they’re cheap, portable and can screen for drugs in mere minutes. It’s just not feasible to send all suspected drug samples to state laboratories, which would be far more expensive and could take days or weeks to return results.

    But these inexpensive tests also lead to false positives at alarming rates, researchers from the University of Pennsylvania found.

    While the actual error rate nationwide is unknown, previous studies by manufacturers have put it around 4%. But the UPenn researchers believe the actual rate is much higher, from 15% to 38%. And a study by the New York City Department of Investigation showed test error rates from 79% to 91% in some correctional settings.

    12 votes
    1. [2]
      sparksbet
      Link Parent
      Oh god, even 4% is pretty high for how much these are used (an error rate that seems low can end up being unacceptably high in absolute terms depending on the size of the population), but if the...

      Oh god, even 4% is pretty high for how much these are used (an error rate that seems low can end up being unacceptably high in absolute terms depending on the size of the population), but if the rates are really that much higher, I hope we see more bans like this in the future.

      6 votes