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.
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"Until police and prisons acknowledge the limitations of these tests, cases like these will keep popping up"
Well, Mr. Unifier could just issue an executive order to all the federal cops to stop using them, and that would reduce the market enough to get rid of them. Might increase the deficit though, so not real likely.
Did anyone else not know that liquid meth was a thing?
I assumed a liquid precursor.
Nyquil?
I came to ask the same thing. The only things I know about meth is that it's the PBR of drugs and it's why I see those tweaky people out and about sometimes.
Methamphetamine freebase. It's an oil. I'm definitely not much of a chemist, but I don't think it would form crystals without a drying agent.
Apparently it smells like geranium leaves.
“And how can Seattle, as such a progressive place and such a wealthy place by then, how can this be?” she thought.
She wanted to know more about how her adopted home got here, how our homelessness crisis reached this state of emergency, the history behind Harborview and our social services. The walk downhill along Skid Road, from an esteemed medical establishment to the city’s poorest, helped her figure out where to start.
Oh, my sweet, innocent dear. It is BECAUSE it's such a progressive and wealthy place that got you where you are with this fucking disaster.
They probably want to make diesel as illegal as meth.
What with climate change and shit it's kinda inevitable. They'll have to deputize a whole new generation of diesel sniffing dogs. The now obsolete meth sniffers will be sent to Detroit to be euthanized by Detroit's finest.
All the chemicals involved in cooking meth—that HAS to be speeding (get it?) up the Global Warming Doomsday Clock!
LITERALLY ALL OF US ARE GOING TO DIE FROM METH!!!!
Unreliable field tests: a feature, not a flaw...
The lesson here - now cops know that anytime they see diesel they have the tools that make it about drugs, seize the vehicle, any cash...
"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!"
It is also completely wrong!
Yeah, I wonder what he said in the press release they put out after the mistake was discovered.
How many gallons of climate-change-inducing chemicals did they get off the street, and explain to me why no matter the outcome, it wasn't a good thing?
Why were these people even detained before trial?
Oh yeah? What on Earth would a trucker be doing with 700 gallons of diesel fuel?
Oh, wait....
"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."
That fact, in and of itself, should be sufficient to overcome probable cause.
The drug tests aren't the problem just like the drug dogs who find evidence of drugs on command aren't the problem, the problem is the war on drugs. Everything the war touches is corrupted, politicians, prosecutors, cops, even medical professionals. How many times have they x-rayed someone, found "irregularities" and kept a person in jail for weeks while they passed their "drugs" only to find out there were none? It's gotten to the point I'd trust a junkie faster than I'd trust any of the above.
First, I didn't know diesel fuel smelled like meth. If not, that should have been the first clue.
Second, 145 false tests out of how many total tests? Is it a 0.1%, 1% or 50% false positive rate?
I notice "Cotton Candy" and "Donut Glaze" both set off a false positive. Donut Glaze is pretty much pure sugar, same as cotton candy. So if it is sugar giving a false positive.... A Lot.
Besides….Cops…..Donuts…..They have a vested interest in fixing this, I’d say!
DEA agent, "Hey this meth smells like diesel fuel. Oh well."