Before they take suspects into custody on narcotics charges, police officers in California and around the country often perform chemical tests on suspicious substances using portable kits. These kits are issued to law enforcement officers because they are fast, inexpensive and using them requires no special training. They also produce extremely unreliable results. The kits contain chemicals that change color when they come into contact with illegal drugs like cocaine, heroin and methamphetamine, but they also can also change color when exposed to benign substances like baking powder, drywall dust and sugar.

These shortcomings are well documented, and police departments in many parts of the country have faced lawsuits after arresting innocent people on drug possession charges. However, the kits remain in use and there are no plans to withdraw them. Few members of the public are aware of the problems associated with drug-testing kits, and research published by groups including ProPublica suggest that thousands of people are behind bars because they pleaded guilty to crimes they did not commit.

These people remain incarcerated because suspicious substances are rarely tested more rigorously when suspects plead guilty. In some parts of the country, prosecutors have taken a proactive approach and overturned hundreds of questionable narcotics convictions. The most recent example of this occurred in Nevada in 2017 when prosecutors in Clark County overturned five drug convictions. All of the defendants in those cases pleaded guilty, and one was sent to jail for eight months. Despite this, police officers in Las Vegas still use the kits.

When criminal defense attorneys represent individuals accused of committing drug offenses, they may seek to have the charges dropped if the only evidence prosecutors have are the results of chemical tests performed in the field. Attorneys could also advise criminal defendants to maintain their innocence when they have done nothing wrong.