In the 1990s, the Las Vegas Metropolitan Police Department began making thousands of arrests every year using inexpensive test kits meant to detect illegal drugs. Officers simply had to drop suspected cocaine or methamphetamine taken from someone’s pocket or the floorboards of their car into a pouch of chemicals and watch for telltale changes in colors. Known as “field tests,” police embraced them as essential in busting drug users and dealers. Local judges became sold on the kits’ usefulness and prosecutors relied on them to quickly secure guilty pleas. Tens of thousands of people every year are sent to jail based on the results of a $2 roadside drug test. Widespread evidence shows that these tests routinely produce false positives, reports ProPublica and the Las Vegas Review-Journal.
By 2010, the police crime lab wanted to abandon its kits for methamphetamine and cocaine. Legal substances sometimes create the same colors as illegal drugs. Officers conducting the tests, lab officials acknowledged, misinterpreted results. New technology was available and was clearly needed to protect against wrongful convictions. Yet the kits remain in everyday use in Las Vegas. In 2015, the police department made some 5,000 arrests for drug offenses, and courts churned out 4,600 drug convictions, nearly three-quarters of them relying on field test results. The department has expanded the use of the kits, adding heroin to the list of illegal drugs the tests can be used to detect. There’s no way to quantify exactly how many times the field tests were wrong or how many innocent people pleaded guilty based on the inaccurate results. Most field tests are accurate and most drug defendants who take plea deals are guilty. The police department maintains it has never established an error rate. Drug arrest and lab testing data show the number could be as low as 10 percent.