Field tests for illegal substances often show false positives

Being falsely accused of a crime is a nightmare that fortunately remains unrealized for the majority of South Carolina residents. However, this was not the case for a college student who was arrested for possession of an illegal drug after a substance on the car tested positive for cocaine, according to USA Today. The sheriff’s officers made the arrest after two separate roadside test kits purportedly came back with the same confirmation. Further testing by the South Carolina Law Enforcement Division went against the initial results; the substance was determined to be innocuous, and the prosecutor dropped the charges. 

Sadly, this is not a unique incident. According to Pro Publica, it is not uncommon for field drug tests to give inaccurate results by “proving” substances to be illicit drugs. Although individual law enforcement departments do not regularly track how accurately these tests perform, one particular state has evidence that over a fifth of the samples that had tested positive for methamphetamine were actually other substances. Additionally, half again of those were not even illegal materials. 

One of the popular roadside tests for cocaine makes use of a chemical that changes color when it reacts with the drug. This chemical is also notorious for producing a color indicative of cocaine when it comes into contact with everyday cleaning solutions, skincare products or other illegal substances. Based on the results of these tests, innocent people are often arrested and then face prosecutors and defense attorneys who assume guilt. 

Confirmation bias can be hard to overcome, and it could be especially dangerous for victims of circumstance when those responsible for holding them innocent until proven guilty use evidence provided by faulty tests.