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Caution: Roadside drug field tests are prone to false positives

All around the country, people are being exonerated after having fallen prey to flawed drug field tests. These tests have been in use for decades without any upgrades, and they have been shown to be prone to false positive results.

The problem was revealed by the nonprofit investigative newsroom ProPublica and the New York Times Magazine.

Every year, tens of thousands of people go to jail after something in their possession tested positive for illegal drugs. Unfortunately, the field drug tests that are used aren’t even admissible in court. Yet police continue to use these roadside drug field tests because they’re cheap — about $2 — and relatively easy to use.

It often shakes out like this. A person is pulled over for a traffic violation and the police ask if they can search the vehicle. Thinking they have nothing to hide, the person agrees to the search. During the search, an unknown substance is discovered. The officer tests it using a roadside field test and it comes up positive for cocaine or methamphetamine. The person is arrested.

They are often assigned a bail that they cannot afford and are forced to remain in jail for weeks or months. Sometimes, prosecutors then offer a sweetheart deal to the defendant, giving them the chance to go home in exchange for a guilty plea. With no other realistic options than sitting in jail and losing everything, they plead guilty.

But the drug tests are notoriously inaccurate. For example, the one that tests for cocaine is known to produce a positive result when exposed to over 80 other compounds, most of which are not illegal. The list includes acne medication and several common cleaners.

How inaccurate are these drug tests?

There isn’t enough data to know. However, the reporters obtained some data from the Florida Department of Law Enforcement lab system. They found that, of the evidence police listed as methamphetamine, about 21% was later found not to be the drug. Among those false positives, about half weren’t anything illegal at all.

There is no central agency regulating the drug tests, and no one is keeping comprehensive records of their use and accuracy. However, after a 1974 study, the National Bureau of Standards stated that these kits “should not be used as sole evidence for the identification of a narcotic or drug of abuse.”

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