War on Drugs

Faulty Police Field Tests Said This Trucker Was Carrying 700 Gallons of Meth. It Was Diesel.

Juan Guzman spent nearly six weeks in jail based on unreliable field tests that have resulted in hundreds of other wrongful arrests.


Police and Drug Enforcement Agency (DEA) agents in Pharr, Texas, thought they had intercepted a massive meth smuggling operation this February. Juan Carlos Toscano Guzman, a Mexican national, spent nearly six weeks in jail accused of transporting roughly 700 gallons of liquid methamphetamine. But it turned out not to be illicit drugs at all, just the result of unreliable drug field tests that have led to hundreds of other wrongful arrests.

The case, first reported by the Fort Worth Star-Telegram, started when a Pharr police officer noticed three men transferring liquid out of large barrels next to a tanker truck. The officer noticed strange crystallization around the barrels and called in backup.

According to the criminal complaint filed against Guzman in federal court, Pharr police officers, firemen, and DEA special agents all tested the liquid in the barrels using drug field tests, and they came back presumptive positive for methamphetamines. The DEA estimated the total haul was 700 gallons of liquid meth with a street value of more than $10 million. The seizure made headlines across the state.

"This massive drug seizure impacts way beyond our region where it was headed," Pharr Chief of Police Andy Harvey said in a Facebook post. "This stemmed from a patrol officer's attention to detail when he observed something out of the ordinary and he used our resources to further investigate. This is great policing!"

But a DEA crime lab would later invalidate those field test results, leading prosecutors to drop their case against Guzman in late March. Guzman's lawyer told the Star-Telegram he was transporting a mix of diesel and oil.

As Reason reported last year, such drug field test kits are manufactured by several different companies and are used by police departments and prison systems across the country. The test kits use instant color reactions to indicate the presence of certain compounds found in illegal drugs, but those same compounds are also found in dozens of known licit substances. And although the tests are fairly simple to use, they're still prone to user error and misinterpretation. 

Because of this, they are generally not admissible as evidence in court, but police still use them to establish probable cause to arrest and jail people. This has led to hundreds of known instances of wrongful arrests and even guilty pleas from defendants facing charges for test results that crime labs would later invalidate.

For example, Atlanta resident Ju'zema Goldring spent nearly six months in the Fulton County jail in 2015 after police said sand from a stress ball in her purse tested presumptive positive for cocaine. She was left in jail for four months after a crime lab concluded that the mysterious powder was sand, not cocaine. A federal jury in Goldring's civil rights lawsuit awarded her $1.5 million earlier this year.

In 2019 in Georgia, a college football quarterback was arrested after bird poop on his car tested positive for cocaine. A Florida man was wrongfully jailed in 2017 after a field test confused his donut glaze with meth.

In 2016, sheriff's deputies in Monroe County, Georgia, arrested Macon resident Dasha Fincher after they found a plastic baggie of blue crystals in her car. A NARK II field test of the substance returned a presumptive positive for methamphetamines, and Fincher was charged with trafficking and possession of meth with intent to distribute. Fincher sat in jail for three months until a state crime lab determined that the substance was blue cotton candy. 

A follow-up investigation by a Georgia news station found that the NARK II test kit produced 145 false positives in Georgia in 2017.

Last year, more than a dozen Massachusetts attorneys said they were falsely accused of sending drugs to their incarcerated clients, who were then put in solitary confinement for receiving legitimate legal mail. (One way that synthetic opioids are smuggled into prison is by soaking papers in the drug.) A class-action lawsuit followed, challenging the Massachusetts Department of Corrections' use of NARK II field tests to detect contraband and punish incarcerated people.

Until police and prisons acknowledge the limitations of these tests, cases like these will keep popping up, and innocent people like Guzman will be deprived of their liberty for doing nothing wrong.