[This story has been optimized for offline reading on our apps. For a richer experience, you can find the full version of this story here. An Internet connection is required.]

HIDALGO COUNTY, Tex. — Crouched low in the brush along the riverbank, Border Patrol agent Robert Rodriguez watched the Mexican side of the Rio Grande, waiting. A norteño ballad drifted from a radio somewhere on a nearby farm, and two pigs cooled themselves at the water's edge, wading to their bellies. For a moment, one of the border's busiest places for illegal crossings looked placid.

Then a raft appeared.

Within seconds it was in the water, a teenage guide steering the current while his boss, an older man, stood watch on the bank. In less than a minute, the teenager delivered a woman and a boy to the U.S. side and they climbed out, shoes sinking in the wet silt.

Rodriguez stepped onto the path to stop them, but the woman and the boy did not run. They wanted to be captured. This is how it works now.

The era of mass migration by Mexican laborers streaming into California and the deserts of Arizona is over. Billions spent on fencing, sensors, agents and drones have hardened the border and made it tougher than ever to sneak into the United States. The migrants coming today are increasingly Central Americans seeking asylum or some form of humanitarian protection, bearing stories of torture, gang recruitment, abusive spouses, extortionists and crooked police.

They know the quickest path to a better life in the United States is now an administrative one — not through mountains or canyons but through the front gates of the country’s immigration bureaucracy.

Last year, U.S. immigration courts received nearly 120,000 asylum claims from migrants facing deportation, a fourfold increase from 2014. Those filings have pushed the number of pending cases before U.S. immigration courts to more than 750,000, collapsing the system and upending President Trump’s sweeping promises to lock down the border.

The extraordinary surge of asylum seekers is testing the limits of whom, exactly, the United States is willing to protect, challenging the stone-carved ideal of America as the place that welcomes the tired and poor, “yearning to breathe free.”

It has also presented Trump with one of the most vexing policy challenges of his presidency, and virtually every measure taken so far has made the problem worse.

Trump this spring deployed a nuclear option — separating parents from their children — in an attempt to stop families from coming. It backfired. The controversy generated by the policy and its abrupt rollback six weeks later handed smuggling guides across Central America a potent sales pitch. They now tell potential customers the Americans do not jail parents who bring children — and to hurry up before they might start doing so again.

Families asking for mercy constitute a greater-than-ever portion of those taken into custody. More than half of all arrests along the Mexican border last month were migrant family members or unaccompanied minors, up from 13 percent in 2013.

This spring, Trump fixated on a caravan of asylum seekers traveling through Mexico, about 300 of whom eventually crossed into the United States. Now, a much larger procession of as many as 7,000 Central Americans is trekking north toward the border, despite threats from the president to stop them with U.S. troops and sever aid to their countries.

There is a sinking feeling, among Department of Homeland Security officials, that more caravans are yet to come and that they will only get larger.

Families are coming in caravans and on their own because it works. Only 1.4 percent of migrant family members from Guatemala, Honduras and El Salvador who crossed the border illegally in 2017 have been deported to their home countries, according to DHS officials.

The United States has neither the detention space nor the legal authority to hold children long enough to process their parents’ claims, so families are typically released from custody to await court hearings that could be months, even years, into the future.

Trump has long derisively referred to this as "catch and release" and used it as an attack line against Democrats. But in the months since ending family separation, Trump has now made it his de facto policy.

The administration has drafted plans to add thousands of detention beds in an attempt to hold parents with children longer. DHS officials have also proposed new rules that would allow the government to withdraw from a 1997 federal court agreement limiting the amount of time children can be held in immigration jails to 20 days.

But in the meantime, so many families are coming through high-volume corridors such as the Rio Grande Valley that Rodriguez and other agents have come to describe them as “non-impactables,” because they say there is nothing they can do to stop them.

As Rodriguez radioed another agent to pick up the woman and the boy, she handed him her Honduran identification card. Cecilia Ulloa was 25. Darwin, her son, was 13. The math took a moment to sink in, and Ulloa appeared to recognize a familiar look of confusion.

“My stepfather,” she said. “It started when I was 10.”

After a decade in prison for rape, her stepfather was free now, stalking them, blaming her for ruining his life, Ulloa said. “He’s going to kill us.” 

Police in Honduras had told her there was nothing they could do, she said, so she and her son left for the United States. They wanted asylum.

Chances were they would be denied. But it could take months, or longer, for the U.S. immigration system to determine whether Ulloa and her son deserve protection. They would probably not be sent back to Honduras anytime soon.

Credible fear

Some migrants’ stories of gang threats and police indifference have a rehearsed quality, suggesting they are concocted. The smuggling guides who charge $10,000 or more for the trip provide transportation and meals, but also coaching, including the key words migrants should say to convince U.S. asylum officers that their fears meet credibility standards.

But there are many with no need to make things up. The countries they are running from have some of the highest murder rates in the world. Their criminal justice systems barely function. Some have been victimized already.

Lisa Brodyaga, an immigration lawyer in South Texas who has worked with Central American migrants since the late 1970s, said adult asylum seekers who appear before immigration judges “are almost all being deported.”

"I think judges felt freer to follow their gut under Obama than they do now," she said.

Migrants have adapted just as quickly. As asylum officers and immigration judges reject more claims, the number of single adults who arrive claiming fear of persecution is dropping. The fastest-growing portion comprises parents coming with children, preventing their long-term detention and significantly reducing the likelihood they will be deported.

Last month, border agents arrested 16,658 individuals who arrived as members of “family units,” an all-time high, up from 9,247 in July.

Migrant advocates have documented cases of rejected asylum applicants being killed after they were sent back. But a full picture is difficult to obtain because U.S. government statistics do not track what happens to deportees once they leave the United States.

DHS officials point to improving public-safety statistics from Central America as evidence that the asylum trend is not driven by worsening violence.

Those fleeing lawlessness and crime are also lured north by job opportunities and the desire to reunite with parents, siblings and other relatives already living here. The United States offers not only safety but also a chance at a dramatically better life.

And with the U.S. unemployment rate at a 50-year low and employers across the Midwest desperate for labor, the Trump-era economy is undermining the Trump-era immigration agenda.

“Migrants from Central America seek asylum in the U.S. to escape gangs, violence and lack of opportunity,” said Doris Meissner, who is policy director at the Migration Policy Institute and ran the U.S. immigration system under President Bill Clinton. “This mixture of humanitarian and economic migration is happening in other parts of the world, too.”

“However, only some of those in peril are actually eligible for asylum,” said Meissner, co-author of the new report “The U.S. Asylum System in Crisis.” “Granting them protection but keeping asylum systems from being overwhelmed or misused requires broad solutions, including attacking the reasons people flee.”

For people like Ulloa and her son, here’s how it works.

Those who cross the border and turn themselves in are interviewed by a U.S. asylum officer to determine whether they have a “credible fear” of facing persecution back home. The Supreme Court has ruled that an asylum-seeker’s fear is considered “well-founded” if there is a 10 percent chance they will face persecution, and those who potentially qualify are referred to an immigration judge.

Between Oct. 1, 2017 — the start of the 2018 fiscal year — and June 30, the period for which the most recent statistics are available, the government received more than 73,000 credible-fear claims, up from 5,000 during all of 2009. Of those 73,000 who were interviewed, 76 percent were found to have a credible fear of return.

The finding does not mean that a judge will eventually grant asylum. Justice Department statistics show that fewer than 10 percent of Central American applicants are awarded asylum, but the process of applying offers a shield from deportation and a toehold, however tenuous, in the United States.

Trump officials view this as a too-permissive approach to asylum claims that amounts to a mile-wide loophole in the American immigration system. U.S. generosity is being exploited by smugglers and cheats, they say, and the dysfunction encourages more to make a dangerous journey. 

Under Trump, asylum denial rates have reached their highest levels in more than a decade. But nearly half of those rulings are issued in absentia, because the applicant does not appear in court. 

That is the breach Trump officials see: If asylum seekers think their case is likely to be denied, they can drop out of the court system and disappear, remaining in the United States illegally. The latest Justice Department figures show U.S. courts issued more than 40,000 removal orders in absentia during the government’s 2017 fiscal year, nearly twice as many as in 2014.

“Saying a few simple words — claiming a fear of return — has transformed a straightforward arrest for illegal entry and immediate return too often into a prolonged legal process, where an alien may be released from custody into the United States and possibly never show up for an immigration hearing,” Attorney General Jeff Sessions said in a September speech to a group of 44 newly hired immigration judges that he said was the largest class in history.

“Our system was not designed to handle thousands of new asylum claims every month from individuals who illegally flood across the border,” he said. “But that is what has been happening, and it has overwhelmed the system.”

'Private' violence

In the absence of a physical wall, the Trump administration is laying down new legal barriers to the asylum process. The U.S. immigration court system is a branch of the Justice Department, not the judiciary, and the attorney general effectively functions as a one-man Supreme Court. In June, Sessions issued a sweeping ruling that overturned the case of a Guatemalan domestic-violence victim who had demonstrated that police failed to protect her from spousal abuse and rape. 

Sessions’s ruling said asylum laws are meant to shelter those facing persecution for political or religious beliefs, or their membership in a well-defined social group, not those fleeing what he called “private” forms of violence. 

“The mere fact that a country may have problems effectively policing certain crimes — such as domestic violence or gang violence — or that certain populations are more likely to be victims of crime, cannot itself establish an asylum claim,” Sessions wrote.

Under Sessions, the Justice Department has attempted to reduce the court backlog by adding dozens of immigration judges and imposing quotas that compel them to process more cases. It has taken steps to prioritize the claims of the most recent arrivals, as a way to discourage asylum seekers from taking advantage of the court backlog. And it has instructed judges and asylum officers to take a more adversarial approach to migrants’ claims. 

U.S. asylum laws were shaped in the aftermath of World War II, when the United States and other Western nations developed international treaties based on the principle of “non-refoulement” — that those fleeing persecution should not be sent back to places where they are likely to killed or persecuted.

Applicants who reached U.S. soil could prove eligibility for asylum on the basis of past persecution or a fear of future abuse on the basis of their “race, religion, nationality, membership in a particular social group or political opinion.”

In practice, historians and immigration scholars say, political considerations have often superseded humanitarian ones. During the Cold War, refugees fleeing communist and left-wing governments in Vietnam, Cuba and Nicaragua were welcomed in large numbers, while those escaping U.S.-friendly military dictatorships in El Salvador and Guatemala were denied.

"The United States has never solely pursued asylum on the basis of humanitarian principles," said Roberto Suro, a migration expert at the University of Southern California and former director of the Pew Hispanic Center. "American approaches have always been ad hoc and driven largely by foreign policy concerns and domestic policy concerns."

Sessions has directed judges and asylum officers to adhere to a narrower definition of “membership in a social group” — the category had been used in recent years to grant protection to victims of domestic violence. 

“An alien may suffer threats and violence in a foreign country for any number of reasons relating to her social, economic, family or other personal circumstances,” Sessions wrote. “Yet the asylum statute does not provide redress for all misfortune.”

The president demonstrated even less patience this spring, when a large group of asylum-seeking Central American families formed a caravan to travel northward. Trump took their journey as a personal affront.

“We cannot allow all of these people to invade our Country,” he wrote on Twitter. “When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came.”

More than 400 caravan members eventually crossed, according to DHS statistics. Among them was Carlos Aldana, who now lives with his partner and young daughters outside Seattle, waiting to see a judge. The monitoring device strapped to his leg has been on so long he barely notices it anymore.

“We go to the park. We go to church and the grocery store,” Aldana said. “It’s beautiful here.”

His family’s asylum claim epitomizes the intertwined push-and-pull factors that bring Central Americans to the United States — and that make it unlikely he, his partner and their two daughters will be allowed to stay.

The family had a small farm near the Caribbean coast, on land purchased with money sent home by a brother working in the United States. When traces of gold were found on the property, Aldana said, he and his siblings invested in mining equipment and began digging.

Then a local crime boss found out about their discovery. He showed up at the property with a carload of men, offering to “go into business together,” Aldana said. Aldana’s family declined, and the man returned and said he had heard others were planning to kill them. He offered protection. Again, Aldana and his siblings refused.

The threats worsened. Then one of Aldana’s brothers was killed. Aldana said his family was too scared to go to the police. “They work for him,” he said of the gangster.

The family fled to another part of Honduras and attempted to start over, but a year later the man found them and the threats resumed, Aldana said.

This time Aldana and his family fled to southern Mexico. They were arrested by Mexican authorities and sent back to Honduras. They tried to start over again.

Worried that he was putting the whole family in danger, another of Aldana’s brothers bid farewell and left. His body was found a few months later, tortured and mutilated. Aldana reported the crime to police, but they made no arrests, he said.

Aldana fled with his family to Mexico a second time, then found out about the caravan. Like others who joined, they saw it as a safe, affordable way to reach the border.

Along the journey, the caravan’s legal advisers warned Aldana he would probably not qualify for asylum because he had been deported from the United States once before, in 2008, when he attempted to come illegally at age 19. 

But he crossed anyway, and like so many Central Americans, his urge to flee is hard to separate from the desire for a better life in the United States.

“I feel safe here. I just want to be able to stay, so my girls don’t have to grow up in a place like that,” he said of Honduras. “I don’t ever want to go back.”

'The most horrifying stories' 

Asylum seekers who make their claims at official border crossings — not on the banks of the Rio Grande — are not breaking the law. But U.S. agents have to let them cross the bridge first.

On a recent morning in South Texas, immigration lawyer Jennifer Harbury walked across the river into Mexico under a blazing sun, waiting for a nun to pick her up. They drove to a Reynosa migrant shelter in a bullet-scarred neighborhood full of cartel lookouts and stash houses used by smugglers to stage illegal crossings.

Harbury is an irritant to U.S. border officials as well as the cartels. She provides free legal advice and assistance to asylum seekers, so the nuns who run the shelter call her often to see whether she can help migrant families desperate for legal advice. Harbury’s pro bono work takes profits away from traffickers, because they charge a “tax” of several hundred dollars to those who cross illegally along the river. They earn nothing from the migrants Harbury escorts to the official border crossing.

Harbury is one of the activists who also help asylum seekers stranded in the no man’s land on the pedestrian bridge over the river. In recent months, U.S. officers have been turning migrants away, telling them to come back later. Harbury and others have criticized the practice as unlawful, but DHS officials say that port officers have multiple responsibilities and that busy border crossings have capacity limits. 

It was Harbury who provided ProPublica with the surreptitious audio recording of a child screaming for her mother that dealt a severe blow to the family-separation policy. She has absorbed the stories of thousands of asylum seekers over the decades and increasingly views her job with the urgency of an emergency responder. She intends to help as many asylum seekers enter the United States as possible, because she believes she is saving their lives.

“These people have the most horrifying stories I have ever heard,” she said. “I don’t think people have better claims than those running from the cartels.”  

The shelter in Reynosa was crowded with newly deported Mexicans, many still carrying their belongings in plastic bags provided by the U.S. government. Immigration and Customs Enforcement had dropped off 85 deportees the previous night, and several complained harshly of bad food and abysmal conditions in U.S. detention.

The nuns had asked Harbury to help a young mother stranded for more than a week, Maria Magdalena Gonzalez, 21, and her son, Emiliano, 3. A gangster in Gonzalez’s home state of Guerrero was threatening to kill her for rejecting his advances, she said. But when she and her son tried to approach the U.S. border crossing a few days earlier to seek asylum, they had been turned away.

With more and more Central Americans showing up at the port of entry, U.S. officers had set up an impromptu checkpoint over the middle of the Rio Grande, blocking them from setting foot on the U.S. side to start the asylum process. 

Those who fail to cross are put at risk, because cartel lookouts ply the Mexican side of the bridge, watching for Central Americans who have been turned away. The migrants are prime targets for kidnapping because criminal groups assume they have relatives living in the United States with enough money to pay a ransom.

Harbury was there to make sure Gonzalez and her son weren’t rejected again.

A nun drove them to the bridge over the river, and Harbury walked alongside them until a Mexican immigration official stood in the way. He had been looking for asylum seekers from Central America, but Gonzalez and her son were Mexican, so there was nothing he could do to detain them. 

He told Harbury the U.S. agents had not been letting asylum seekers through, or were making others wait three or four days to be allowed to approach the American side.

Harbury, Gonzalez and the boy continued walking until three American officers blocked them halfway across the bridge. “We want asylum,” Gonzalez said softly, more a question than a demand. An agent told her to stand aside and wait.

Harbury asked how long, and the officers said it could be several hours, perhaps days. She sat down on the pavement with Gonzalez and the boy. “We’ll wait,” she said.

The officers appeared to notice a reporter taking notes and called a supervisor. He arrived and waved everyone through.

Gonzalez reached the inspection booth and pushed her paperwork forward. Harbury gave her a hug and an invitation to dinner. Then the officers directed Gonzalez and her son to an adjacent waiting room. 

“They made it,” Harbury said.

She waved goodbye through the glass. The room wasn’t full, not even close. There were more than 60 chairs in the waiting area, and all but two were empty.