NOGALES, ARIZONA — We know that illicit fentanyl is flowing into the U.S. from Mexico. Yet we rarely hear from the couriers who smuggle most of it through legal ports of entry. This is one of their stories.

Just before midnight on Aug. 4, 2021, Haley tried to cross the border from Mexico back into Arizona, where she lived. She was carrying 1,000 fentanyl pills inside her body.

"That was the first time I've ever done it," Haley says. "It was just a sudden decision that I made at the last moment."

At the time, Haley was struggling with addiction to methamphetamine. She'd lost her job during the COVID-19 pandemic and then lost custody of her three children. (Haley, 32, asked not to use her last name in order to protect her children's privacy.)

When a man she knew offered her a chance to make $500, Haley took it.

"I'm very ashamed that I didn't know better with carrying it over," she says. "When you're on drugs, your mind's not fully there. You're not fully thinking. You're just like, OK, I can get this over with and get my bills paid, you know? You're not thinking about what you're doing to your body, what you're doing to others."

Fentanyl and other drugs are often smuggled by couriers

Thousands of pounds of fentanyl are flowing into the U.S. from Mexico every month. Yet we rarely hear much about the couriers, also known as mules, who smuggle much of it through legal ports of entry.

Prosecutors and defense lawyers say Haley's story is typical; the vast majority of illicit fentanyl — close to 90% — is seized at official border crossings. Immigration authorities say nearly all of that is smuggled by people who are legally authorized to cross the border, and more than half by U.S. citizens like Haley. Virtually none is seized from migrants seeking asylum.

Sometimes fentanyl and other drugs are concealed inside tractor-trailers carrying loads of legitimate cargo into the U.S. More often, authorities say, it's hidden in passenger cars or on the bodies of pedestrians.

"There's a popular misconception that it is these giant seizures that are driving the numbers. And that's not it," says Adam Gordon, a federal prosecutor in San Diego, one of the busiest crossing points for fentanyl on the U.S.-Mexico border. "The cases that we see every day are individuals who have five kilos of fentanyl and 10 kilos of methamphetamine. And those cases are happening constantly."

Law enforcement officials say drug cartels routinely recruit couriers or mules to get their products across the border. They're sophisticated in choosing these targets.

"They're looking for somebody we're not going to pay a lot of attention to," says Michael Humphries, the port director in Nogales, Arizona, where Haley attempted to cross back from Mexico.

"They target certain people and they offer money to drive through," says Humphries, who spent decades with U.S. Customs and Border Protection trying to catch smugglers at official ports of entry. "I've been at this for over 36 years, and it's been like that forever."

What has changed is that synthetic opioids such as fentanyl are more potent and cheaper to make than organic drugs like heroin or cocaine. These new drugs are harder to catch because concealment in cars or on the bodies of couriers is easy.

"The cartels are smart. They're going to pick couriers that they think are going to be more successful at that point in time," says Stefani Hepford, an assistant U.S. attorney in the Tucson office who's prosecuted dozens of smuggling cases. "I've seen 20-year-old couriers. I've seen 60-year-old couriers. It's impossible to generalize."

The ideal candidate, Hepford says, is someone who is authorized to cross the border, and goes back and forth often because they won't attract attention from customs officers at the port.

Couriers are often in "desperate straits"

Given those criteria, Haley wasn't a great choice to be a courier. "I don't go to Mexico. That's not something I do," she says.

When she presented herself at the port of entry in Nogales that night in 2021, the officer on duty asked what she was doing in Mexico and directed her to secondary inspection.

"I already knew, you know, I was caught. It was done," Haley says. "In my heart, I knew that I was doing wrong, you know? So, I started freaking out, and I kind of told on myself."

Haley was arrested and charged. She pleaded guilty and went to prison. There, she met lots of women who had carried drugs through the ports — some of them repeatedly.

"I've heard girls talk about, you know, I did it, I did it, I had it inside of me or, you know? And I'm just like, aren't you lucky? I got caught my first time," she says.

"People do it over and over again, because the money is so good," Haley says. "These girls are so used to their money amount, that's the life they want. That's the life they know."

Law enforcement officials say there is no shortage of people willing to do this work.

"A lot of it is driven, unfortunately, by addiction," says Gordon, the prosecutor in San Diego.

"You're looking at a population that attempts to cross the border into the United States carrying these drugs who are usually not being paid very much. Think of anywhere from $1,000 to $5,000 to drive a vehicle across," Gordon says. "Usually they're in very desperate straits."

"Typically, my clients have hit rock bottom," says Jessica Turk, a defense lawyer in Vail, Arizona, just outside of Tucson. Turk takes on clients who can't afford a private lawyer and who are often charged with smuggling drugs or people into the U.S. She says many of them are struggling with addiction.

"Their drug addiction has put them on the street, or they're living in a shed or they're living in a car," Turk says. "They need money to fuel an addiction. And this is an opportunity that regularly presents itself to people in this area."

Haley was recruited by an acquaintance, not a cartel. But in other ways, her story follows a similar arc.

By the time she made the decision to carry fentanyl across the border, her life was falling apart. Haley had been addicted to meth once before when she was younger. She got sober and stayed that way for nine years. She was living in Tucson with her children. But a few years ago, things took a turn.

"I went through a very hard breakup that really sent me into a spiral where I went into drugs really heavy again," Haley says. "I couldn't be without it, almost. And then it just became a full-blown addiction where I was scared that if I got sober, it was going to hurt."

Eventually Haley's children were taken away by child protective services. Haley says she was fighting to get her children back. She had lost her job during the pandemic and was having trouble finding a new one.

"I had to make sure that I was doing the right things and pay my bills. And I'm trying to get sober," she says. "And I just felt like the world was against me."

A steep increase in fentanyl seizures

Fentanyl seizures have been climbing across the border, especially in California and Arizona.

Homeland Security Secretary Alejandro Mayorkas traveled to Nogales in March to announce a stepped-up enforcement effort known as "Operation Blue Lotus."

In May, federal prosecutors in Tucson announced charges against 10 people who were accused of smuggling at ports of entry or caught at nearby vehicle checkpoints. Five are U.S. citizens and five are Mexican nationals who had permanent residency or other legal authorization to be in the U.S.

Authorities say the operation has led to the seizure of thousands of pounds of fentanyl. Though they also estimate that they're apprehending just a fraction — roughly a quarter — of all the fentanyl that's smuggled at the border.

As the number of overdose deaths from fentanyl keeps climbing, smuggling has become a major issue in Washington, D.C., and the subject of intense debate.

Some of the leading voices in the Republican Party reject the official narrative that it's mostly coming through the ports. They believe there's a lot more fentanyl that's not being caught.

"The video cameras placed by ranchers on the border show the cartel members in camouflage outfits wearing carpet shoes and backpacks full of fentanyl pouring into our country," said Rep. Mark Green of Tennessee, the chairman of the House Homeland Security committee, at a field hearing in Texas in March.

"There's a tremendous amount of illicit fentanyl and meth crossing between the ports of entry," Rep. Clay Higgins of Louisiana stated at a hearing in February.

It's true that the Border Patrol does catch some fentanyl smuggled between the ports. John Modlin, chief of the Border Patrol's Tucson sector, testified at the same hearing in February.

"Last year, we seized about 700 pounds of fentanyl," Modlin stated. "That was encountered – 52% of that, so the majority of that – was encountered in the field. So that is predominantly being backpacked across the border."

The Border Patrol in Tucson is on pace to surpass that total this year. Even so, that's just a small fraction of the 10,000 pounds of fentanyl seized in Nogales and other ports in Arizona.

Still, Republicans say there could be far more fentanyl hiding in the backpacks of smugglers that the Border Patrol is not catching, because agents are distracted by dealing with migrants crossing the border. They argue that's allowing smugglers to sneak more of their product across in the wide stretches of terrain between the ports.

Jim Chilton says that's exactly what is happening on his ranch about an hour's drive northwest of Nogales. Chilton raises cattle on a 50,000-acre ranch that stretches from Arivaca, Arizona, south to the border. He'll tell anyone who asks about how smugglers use the trails through the jagged mountains on his ranch.

Chilton says his video cameras have captured images of more than 3,000 people over the past two years.

"Nobody's in street clothes," he says. "They are in camouflage clothing, camouflage backpacks, and they're wearing carpet shoes."

Carpet shoes are like slippers made of carpet that go over regular shoes. Migrants regularly use them in an effort to make it harder for the Border Patrol to track footsteps. A big pile of carpet shoes from migrants who've crossed on his land sits in Chilton's driveway.

That doesn't prove they were carrying drugs – though Chilton believes many of them were.

"I know from the Border Patrol that about 20% of the 3,000 the last couple of years are packing hard drugs," he says. "The evidence appears to be it's all hard drugs. Fentanyl, cocaine, heroin, meth."

By all accounts, there is a significant amount of human smuggling in the mountains and desert around Nogales as migrants pay smugglers thousands of dollars to sneak them into the U.S. without detection. Borderwide, CBP estimates there have been more than 1 million known "gotaways" over the past two years.

Still, top immigration officials in Washington are skeptical that migrants and others who sneak across the border are carrying large quantities of fentanyl or other drugs.

"Our analysis, our intelligence continues to point to most of what's being smuggled at the ports of entry," said Troy Miller, the acting commissioner of Customs and Border Protection, in an interview.

"I'm not saying that there's no narcotics being smuggled or hard narcotics being smuggled between the ports of entry," Miller says. Still, it's less risky for drug cartels to smuggle fentanyl and other drugs through the ports of entry, he argues.

"They're able to hide the narcotics in legitimate travel. They're able to surveil the travelers. They have preexisting logistics routes to move the narcotics quicker," Miller says.

And smugglers have become very good at concealing fentanyl deep in passenger cars.

"We don't open the trunk and, hey, there's a bag of fentanyl powder or pills," says Humphries, the port director in Nogales. "We're looking at tires, gas tanks, roofs, floors, seats. Anywhere you can imagine."

Humphries says smugglers have even hidden inside the car's engine.

"One time they pulled out two pistons from the engine," he says. "The void created by that was filled with narcotics, and the engine was still running."

Haley is trying to start over

When couriers are caught with drugs at the border, it's often their first serious criminal offense. That was the case for Haley. She cooperated with prosecutors in exchange for a lighter sentence and served six months in prison.

The hardest part, she says, was losing custody of her children.

"My ex-sister-in-law had to adopt my kids because I got sentenced and I was in jail," Haley says. "Yeah, that was hard."

Haley has been sober for more than 18 months. She has a job, and just bought a car. She gets to see her kids again — rebuilding their trust, she says, has been difficult.

"Six months ago from today, I could tell you my kids didn't really want to be around me. They don't want to spend the night with me," she says. "Today they are always like, 'Mom, can we spend another night with you, mom?'"

In hindsight, Haley says, getting caught at the border on her first attempt was actually good luck. Considering how much fentanyl she was carrying inside her body, things could have turned out much worse.

"That's a lot of pills. I mean, it's enough to kill a thousand people, right?" she says. "If they would've opened inside of me, I'd be dead. It's a very scary thought. The thoughts I don't like to think about a lot, you know?"