The Field Drug Test Problem: Inaccurate, Widely Used, and a Pervasive Injustice in North Carolina
This is part two of a two-part series. For an overview of these tests, check out part one.
The Problem
In Iowa, a mother went public after her daughter was expelled from school when a cookie she brought to class tested positive for marijuana on a colorimetric field drug test. The cookie contained no marijuana. In a Colorado hospital, an 80-year-old woman was accused of cocaine possession after a substance found in her purse had a positive reaction to that same drug test. It wasn't cocaine.
These cases broke through because the injustice was impossible to ignore. But they frame a quieter, more pervasive problem playing out daily on roadsides and in courtrooms across the country.
A December 2023 study by the Quattrone Center at the University of Pennsylvania Carey Law School found that more than 750,000 people are arrested annually in the United States based on field drug tests known to produce false positives. Approximately 30,000 of those arrests each year involve people who are entirely innocent. The problem has been documented for decades. In 1974, the Commerce Department's National Bureau of Standards stated that roadside drug tests "should not be used as sole evidence for the identification of a narcotic or drug of abuse." The Department of Justice echoed that warning within the decade, but fifty years later, they are still in use.
The harm doesn't fall evenly. Black drivers are stopped more frequently than white drivers relative to their share of the driving population and are nearly twice as likely to have their vehicles searched. The Quattrone Center study found that Black people experience erroneous drug arrests from inaccurate field tests at a rate three times higher than their white counterparts.
How the Current Project Started
In Harris County, Texas, an administrative practice meant that drug evidence was still sent to crime labs for testing even after defendants had already pleaded guilty, inadvertently creating a paper trail that exposed widespread errors. What researchers and prosecutors later found was stark. In a review of wrongful drug convictions, 94 of 140 exonerations in Harris County in 2016 and 2017 involved cases built on inaccurate field tests. A separate ProPublica and New York Times investigation found that 212 people had pleaded guilty to drug charges based on Houston Police Department field tests later contradicted by crime lab results showing no controlled substance.
What the Harris County data made visible was something happening invisibly everywhere else: innocent people routinely plead guilty before a lab ever confirms the result, because the alternative is sitting in a cell while they wait. In most states, lab tests can take up to 6 months, and sometimes as much as a year.
Translating that research for policymakers and the public is now the work of Marcus Pollard, a policy analyst at the Wilson Center, and Rebecca Brown, who consults for both the Quattrone Center and the Wilson Center.
The Wilson Center has focused on understanding how this issue plays out locally in North Carolina. Through surveys of law enforcement agencies, the Wilson Center collected data on how field drug tests are actually being used in the state. That research informed a one-pager available on the topic, and, in partnership with Duke Justice Project, informational videos reaching general audiences on social media. The Center has also interviewed community members who may have been directly impacted by false positive results.
Colorado and North Carolina: Legislative Responses
Colorado House Bill 26-1020 passed earlier this year with unanimous votes in both chambers. Under the legislation, when a colorimetric test is used, and a person is suspected solely of misdemeanor drug possession, an officer must issue a summons rather than detain the individual. Before any plea can be entered, the court must advise the defendant that colorimetric tests carry known error rates and that the defendant has the right to request laboratory testing.
In North Carolina, Representative Phillip Anthony Rubin (D) is working with Senator Gregory Allen Chesser II (R) to introduce legislation establishing a pilot program that would bring more accurate testing devices to select departments and track outcomes across testing methods. Advanced portable devices analyze an actual chemical fingerprint rather than a broad molecular characteristic. A 2018 study by the National Institute of Justice found they offered meaningful advantages in specificity and were better equipped to identify the synthetic drugs increasingly appearing on the street. Although these devices cost more upfront than colorimetric field tests, the pilot program is designed to test whether they provide long-term gains in accuracy, community trust, and officer safety.
Nobody benefits from wrongful drug arrests. Not the community, which loses trust in law enforcement every time someone is detained for owning a Splenda packet or gym chalk. Not law enforcement, whose officers face real risk when continued handling of unconfirmed substances puts them in unnecessary contact with compounds that may include fentanyl. And not the courts, processing unnecessary prosecutions, or overcrowded jails, holding people whose test results haven't been confirmed. Better field testing isn't just a protection for the accused. It's a more accurate instrument for the work law enforcement is actually trying to do.