“The well-documented problem with these kits is that the compounds they test for are not exclusive to illicit drugs and are, in fact, found in dozens of legal substances. That is to say, they’re better at telling if something isn’t a drug than if it is one. This is why they’re used in laboratory settings as preliminary screeners. But in the criminal justice system, they’re considered probable cause to make an arrest.
As a result, many people have been arrested for absurd items. Over the years, officers have jailed innocent people after drug field kits returned “presumptive positive” results on bird poop, donut glaze, cotton candy, and sand from inside a stress ball.
…
Despite appearing easy to use, the tests can still be performed incorrectly or produce muddy results, which leaves suspects’ fates to the subjective opinions of police officers.”
https://reason.com/2026/02/23/he-was-jailed-for-fentanyl-it-was-really-his-legal-prescription-meds