As lawmakers in Washington continue to negotiate over immigration policies, they'll have to grapple with a fundamental disagreement about the link between immigrants and crime.
Elected officials from Pennsylvania to Arizona have argued that undocumented immigrants contribute to higher crime rates, but some social scientists tell a different story. They argue that first-generation immigrants actually make their communities safer and they point to some of the nation's biggest cities as proof.
Two decades ago, Brooklyn's Sunset Park neighborhood was nicknamed "Gunset Park" because of its high crime rates. Today, the commercial avenues are bustling, and once-empty storefronts are now full of businesses catering to immigrants from Latin America and Asia and their young families.
"When a lot of immigrants come to communities, crime tends to drop," says Philip Kasinitz, who teaches sociology at the City University of New York Graduate Center. "And, of course, it's quite the opposite of what many people think."
Police statistics show that Sunset Park is much safer than it was 20 years ago. Homicides are down more than 90 percent. Crime rates have dropped all over New York City since 1990 but especially in neighborhoods that have high immigration.
To be fair, Kasinitz says, "it's absolutely not something you can attribute to any one cause." He points to a variety of potential factors, including changes in policing and the end of the crack epidemic.
"But I would say, among the things that are on the positive side of the ledger, has been this dramatic increase in immigration," Kasinitz says. "The fact that you've got more people, that you don't have empty storefronts, that it's not deserted, sort of decreases the conditions that can create crime."
And it's not just happening in New York City. Across the country, cities with high rates of immigration, like Los Angeles, Houston and San Diego, also have much lower crime rates than they did 20 years ago.
Some social scientists say that's not a coincidence. Robert Sampson of Harvard University argues that first-generation immigrants make their communities safer by working hard and raising families.
"You don't migrate to the United States from countries around the world on a whim. It takes planning," Sampson says. "And for the most part, it is driven by economic motivations. People want a better life. They're seeking to get ahead. And those are the very factors that tend to be associated with lower crime."
Sampson says this seems to be true whether or not the immigrants have entered the country legally. But some say there is a difference when it comes to crime.
"You cannot intermingle immigrants with those that are in the country illegally," says Lou Barletta, former mayor of Hazleton, a small city in northeastern Pennsylvania that experienced an influx of Latino immigration in the early 2000s. In 2006, one of Barletta's constituents was murdered by a man who was in the country illegally.
"The shooter was arrested eight times before he came to Hazleton," says Barletta, now a member of Congress. "Should not have even been in the country, let alone in our city, taking the life of an innocent man. That was the final straw."
Hazleton passed tough laws still tied up in court that made it a crime to hire or rent to undocumented immigrants.
Pennsylvania isn't the only state where lawmakers have tried to curb immigration in the name of public safety. Arizona Gov. Jan Brewer has also said her state's tough anti-immigration law is necessary for the safety of Arizona residents.
"I feel as governor I have a responsibility to protect the citizens, she told Fox News in 2010. "We've been inundated with criminal activity. It's just it's been outrageous."
But Brewer's critics say there's simply no evidence that illegal immigrants are driving up crime rates. And even the Center for Immigration Studies in Washington, which opposes increased immigration, came to the same conclusion.
"There's no evidence that immigrants or even illegal immigrants are necessarily any more or less likely to be committing crimes than the population at large, says Jessica Vaughan, the center's director of policy studies. "It's just that they tend to be associated with certain types of crimes drug trafficking, for example."
There is evidence that immigrants are overrepresented in local prison systems in Arizona and elsewhere. But overall, violent crime is actually lower than you would expect along the U.S. border with Mexico, says Ramiro Martinez, who teaches criminology at Northeastern University.
"In Texas, homicides are actually a little bit lower in border counties than they are in the rest of the state," Martinez says. "Not only in Texas, but also in New Mexico and Arizona, in California more immigrants means less crime."
That finding may run counter to the public perception that immigrants contribute to higher crime rates. But if lawmakers in Washington look to the research of Martinez and others, they'll find a growing body of evidence to the contrary.