Author Valeria Luiselli began working as a volunteer interpreter at New York’s federal immigration court in 2015. She has since heard many disturbing accounts of unaccompanied children travelling through her home country, Mexico

“Why did you come to the United States?” That’s the first question on the intake questionnaire for unaccompanied child migrants. The questionnaire is used in the federal immigration court in New York City, where I started working as a volunteer interpreter in 2015. My task there is a simple one: I interview children, following the intake questionnaire, and then translate their stories from Spanish to English.

But nothing is ever that simple. I hear words spoken in the mouths of children, threaded in complex narratives. They are delivered with hesitance, sometimes distrust, always with fear. I have to transform them into written words, succinct sentences and barren terms. But the children’s stories are always shattered beyond the repair of a narrative order. The problem with trying to tell their story is that it has no beginning, no middle, and no end ...

Some compare La Bestia to a demon, others to a kind of vacuum that sucks distracted riders down into its metal entrails

The fifth and sixth questions are: “What countries did you pass through?” and “How did you travel here?” To the first one, almost everyone immediately answers “Mexico”, and some also list Guatemala, El Salvador and Honduras. To the question about how they travelled here, with a blend of pride and horror, most say: “I came on La Bestia” – which literally means “the beast”, and refers to the freight trains that cross Mexico, on top of which as many as half a million Central American migrants ride annually. There are no passenger services along the routes, so migrants have to ride atop the rail cars or in the recesses between them.

Thousands have died or been gravely injured aboard La Bestia, either because of the frequent derailments of the old freight trains, or because people fall off during the night. The most minor oversight can be fatal. Some compare La Bestia to a demon, others to a kind of vacuum that sucks distracted riders down into its metal entrails.

And when the train itself is not the threat, it’s the smugglers, thieves, policemen or soldiers who frequently threaten, blackmail or attack the people on board. There is a saying about La Bestia: “Go in alive, come out a mummy.” But despite the dangers, people continue to take the risk. Children certainly take the risk. Children do what their stomachs tell them to do.

The question I feel most ashamed of

Question seven on the questionnaire is: “Did anything happen on your trip to the US that scared you or hurt you?” The children seldom give details of their experiences along the journey through Mexico upon a first screening, and it’s not necessarily useful to push them for more information.

What happens to them between their home countries and their arrival in the United States can’t always help their defence before an immigration judge, so the question doesn’t make up a substantial part of the interview. But, as a Mexican, this is the question I feel most ashamed of – because what happens to children during their journey through Mexico is always worse than what happens anywhere else.

Facebook Twitter Pinterest A priest blesses the coffins of 16 Hondurans, discovered with another 56 murdered migrants in a mass grave in San Fernando in 2010. Photograph: Edgard Garrido/Reuters

The numbers tell horror stories ...

Rapes: 80% of the women and girls who cross Mexico to get to the US border are raped on the way. The situation is so common that most of them take contraceptive precautions as they begin the journey north.

80% of the women and girls who cross Mexico to get to the US border are raped on the way

Abductions: in 2011, the National Human Rights Commission in Mexico published a special report on immigrant abductions and kidnappings, revealing that the number of abduction victims between April and September 2010 – a period of just six months – was 11,333.

Deaths and disappearances: though it’s impossible to establish an actual number, some sources estimate that, since 2006, around 120,000 migrants have disappeared in their transit through Mexico.

Beyond the terrifying but abstract statistics, many horror stories have recently tattooed themselves in the collective social conscience in Mexico. One specific story, though, became a turning point.

On 24 August 2010, the bodies of 72 Central and South American migrants were found, piled up in a mass grave, at a ranch in San Fernando, Tamaulipas. Some had been tortured, and all had been shot in the back of the head. Three migrants in the group had faked their deaths and, though wounded, survived. They lived to tell the complete story: members of the drug cartel Los Zetas had perpetrated the mass murder after the migrants had refused to work for them and did not have the means to pay a ransom.

I remember the dark days when this news broke out in Mexico – thousands or perhaps millions of people in front of newspapers, radios and TV screens, all of them asking: How? Why? What did we do? Where did we go wrong, as a society, to make something like this possible?

Even now, we don’t know the answer. No one does. What we do know is that, since then, hundreds of additional mass graves have been discovered. Every month, every week, they continue to be discovered. And even though the story of “Los 72” changed the way in which both Mexican society and the rest of the world views the situation of migrants crossing Mexican territory, nothing has actually been done about it.

The story of a boy

I recall every nuance of the first story I heard and translated in the federal immigration court. Perhaps only because it was the story of a boy I encountered again, a few months later, and have since kept in close contact with. Or perhaps because it’s a story condensed in a very specific, material detail that has continued to haunt me: a piece of paper the boy pulled from his pocket toward the end of his interview, the creases and edges worn.

He unfolded it gently, slowly, treated it with the same careful precision a surgeon might have when making a decisive incision. He laid it in front of me on the table. As I skimmed through it, still unsure about what he was showing me, he explained that the document was a copy of a police report he’d filed more than a year and a half ago.

Facebook Twitter Pinterest Border agents found this 17-year-old Guatemalan freezing in the Rio Grande, having fallen off the raft carrying him to the US. Photograph: Michael Robinson Chavez/LA Times via Getty

The report stated in three or four type-written sentences, all in capital letters and with some grammatical mistakes, that the subject in question raised a complaint against gang members who waited for him outside his high school every day, frequently followed him home, and began threatening to kill him. It ended with the vague promise to “investigate” the situation.

After showing it to me, the boy folded the document back up and put it in his pants pocket, rubbing his palm now and then against the denim, like he was activating a lucky charm.

When our first day of work in court was over, my niece and I took the A train back home. As our subway sped uptown along dark tunnels, through stations, past ghostly strangers waiting on platforms, the image of that piece of paper came back to me, insistently, with the strange power of symbols.

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It was just a piece of paper, damp with sweat, eroded by friction, folded and tucked inside a boy’s pocket. Originally it had been a legal document, a complaint filed by a boy hoping to produce a change in his life. Now it was more of a historical document that disclosed the failure of the document’s original purpose, and also explained the boy’s decision to leave that life.

In a less obvious but equally material way, the document was also a road map of a migration: a testimony of the 5,000 miles it travelled inside a boy’s pocket – aboard trains, on foot, in trucks, across various national borders – all the way to an immigration court in a distant city, where it was finally unfolded, spread out on a mahogany table, and read out loud by a stranger who had to ask that boy: “Why did you come to the United States?”