Imagine having your house raided by police because the wet tea leaves in your trash looked somewhat like marijuana. Imagine being pulled over, arrested and jailed for a month for possessing homemade soap that looked like it could be cocaine.
These scenarios may sound far-fetched, but they are true stories. And they are just some of the many horrible consequences of police drug tests used out in the field (rather than in a lab). Many of these tests are highly unreliable, yet they often provide enough "evidence" for police to obtain search warrants and for prosecutors to coerce innocent defendants into pleading guilty.
Many of these field tests show results through color changes (when a sample of the suspected drug is dropped into a certain liquid, for instance). In the marijuana case mentioned above, police used the "NarcoPouch KN reagent test." It is supposed to test for the presence of cannabis, and many officers apparently think that the tests are conclusive. But in one study, researchers used the test on 42 legal plant products, and 33 of them falsely tested positive for marijuana. The plants tested included common ones like basil, spearmint and peppermint.
One test, used to detect cocaine, involves dropping a sample into a chemical called cobalt thiocyanate. If it turns blue, the tested substance could be cocaine. Then again, it could also be one of more than 80 other compounds - many of them legal.
While inaccurate field tests could be cleared up later in lab studies, this takes a lot of time. And for some defendants, getting arrested can essentially mean losing their job. Moreover, some jurisdictions allow guilty pleas based solely on field tests. If prosecutors then threaten defendants with harsh jail sentences, the defendants may feel pressured to plead guilty, even if they know they weren't in possession of drugs.
From a policy perspective, these field drug tests either need to be dramatically improved or prohibited altogether. But for individuals, the lesson here is more basic: if you have been charged with a drug crime, please seek the help of an experienced criminal defense attorney right away. It may be the only way to ensure that you don't become another casualty of these pseudoscientific tests.