EL PASO, Texas -- Among the 11 million undocumented immigrants in this country, some 40 percent entered the United States legally with a temporary visa. But once they arrived, they decided to stay. Tracking them down is one of the biggest challenges facing the Department of Homeland Security (DHS).
Worldwide, people who wish to take a vacation or study in the United States must start at their nearest U.S. Consulate.
At the consulate in Ciudad Juárez, across the border from El Paso, Texas, staff can process up to 1,000 applications a day. Applicants must fill out detailed paperwork, turn in a photograph of themselves, provide fingerprints and be interviewed by a consular agent.
"People have to demonstrate what we call ties to their country of origin," said Olga Bashbush, a spokeswoman for the U.S. Consulate in Juárez. "If you're an adult, that means you have job here. If you are student, that you're going to school, that you have family, relatives, you have some sort of life to go back to."
In other words, the consulate wants to be sure you'll go home before your visa expires. Non-immigrant visas come in several varieties, including one for tourists, another for temporary workers and a third for students.
Last year close to 9 million people worldwide received temporary visas to the U.S.
One of tourists who decided to stay is a 24-year-old Argentinean woman who asked not to be named.
"I came to the US when I was 14-years old," she said. "I came like most people on vacation to go to Disneyland ... and after the three months I stayed here."
She overstayed her visa and now lives in California, where she attends college.
"I began to be involved in school, participate in clubs, honor classes, I was in the tennis team, so I thought, 'This was like a dream,'" she said.
But not entirely. This student can't legally drive or work in the United States. And unless she commits a serious crime, she's unlikely to get caught.
Historically, the U.S. government hasn’t aggressively pursued visa violators, said researcher Edward Alden. He studies immigration policy for the Council of Foreign Relations in Washington.
"It's not surprising that a fair number of people thought, 'Well this is a way to come to the United States and continue to live in the United States,'" Alden said.
That lack of enforcement has created problems for the United States.
"Immediately the concern about visa overstays is that it potentially could be a way for terrorists to come and remain in the United States," Alden said. "Several of the 9/11 high jackers had come on legal visas and then overstayed."
After 9/11, DHS started programs to prevent potentially dangerous foreigners from getting a temporary visa. Other programs attempt to better track foreigners. For example, the U.S. Visit Program collects biographical data and fingerprints from foreign visitors. Alden said the program is fairly successful at tracking arrivals and departures from airports. But land crossings are another story.
At the southern ports of entry customs agents document the entry of all travelers. But on the other side no one is tracking their exits. With 350 million southern border crossers each year, DHS claims tracking exits may be logistically and financially unrealistic. Media liaisons from multiple DHS branches refused to be interviewed for this story.
Reporters aren't the only ones searching for answers. California Senator Dianne Feinstein questioned DHS Secretary Janet Napolitano at a Congressional hearing last month.
"For many years I've been trying to get data on visa overstays from each country to no avail so far," Feinstein told Napolitano at the hearing.
Napolitano responded by promising to have more overstay data later this year. The issue is a critical puzzle piece in the ongoing debate over immigration reform.
Alden, of the Council on Foreign Relations, said DHS can take simple measures to help reduce the number of visa overstays. He suggests immigration officials send foreigners an email notice a couple weeks before their visa expires.
"There's plenty of social science evidence that individuals are far more likely to follow the law if they think someone is watching them," he said.
Without stricter enforcement, critics contend the problem of visa violators will simply continue.