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A frequent argument of those proposing tougher illegal immigration policies is that illegal immigration goes hand-in-hand with more crime. They cite the fact that illegal immigrants must already live outside the law and suggest that the violent drug cartels operating across Mexico's border could bring their criminal behavior into the U.S. Are these arguments right? Here are cases for and against.

Extreme Enforcement Increases Crime The Washington Post's Spencer Hsu reports that "police chiefs from several of the state's and the nation's largest cities" agree that "Arizona's new crackdown on illegal immigration will increase crime in U.S. cities, not reduce it, by driving a wedge between police and immigrant communities. ... Arizona's law will intimidate crime victims and witnesses who are illegal immigrants and divert police from investigating more serious crimes." These police chiefs are not arguing that any immigration enforcement increases crime, only that Arizona-style extreme enforcement can increase crime.

...One Place Where That Wasn't The Case Prince William County, a Virginia suburb of Washington DC, became notorious in years past for its Arizona-like extreme immigration enforcement. National Review's John Miller points out that "crime rates are at a 15-year low" in the county. "The latest numbers are part of a trend that started long before the county took a stand against illegal immigration . One thing is certain: The county's current policy has not led to more crime."

Immigration Sanctuaries Don't Reduce Crime National Review's Heather MacDonald looks at the other extreme: Sanctuary cities. "This standard argument in favor of local sanctuary policies has never been tested empirically by comparing witness involvement in sanctuary and non-sanctuary cities. As Pinal County Sheriff Paul Babeu, head of the Arizona Sheriff's Association and a supporter of SB 1070, points out, cooperation from illegal aliens is already low. ... local governments have been creating unofficial amnesties through their sanctuary laws for years. Those don't seem to have worked out so well."

Immigration Crime vs 'Serious' Crime The Moderate Voice's Jason Arvak makes the distinction. "Supporters of the law point out that illegal immigration is a crime. Ok, fair enough. But how serious of a crime is it? Does anyone die or get injured from a poor guy crossing a border looking for work picking tomatoes? Of course not. Yes, some illegal immigrants are criminals or drug runners or human traffickers, but so are a lot of citizens and legal residents."

Crime in Immigrant Communities It exists, says Doug Mataconis, which is why over-enforcement would be so counter-productive. "Communities where immigrants, legal and illegal, live are also likely to be the targets of criminal activity for a variety of reasons. If the impression is created that the local police are little more than agents of the Federal immigration authorities, then, obviously, someone who is the victim of a crime is going to be less likely to report that crime, or cooperate with investigating officers, if they believe that they risk deportation."

As Illegal Immigration Rises in Phoenix, Crime Falls The Wall Street Journal's Evan Perez reports that, from 2008 to 2009, violent crime "plunged 16.6% in Phoenix, despite a perception of rising crime that has fueled an immigration backlash." Violent crime fell 5.5% nationally. "For the first quarter of 2010, violent crime was down 17% overall in the city, while homicides were down 38% and robberies 27%, compared with the same period in 2009. Arizona's major cities all registered declines." CATO's Daniel Griswold adds, "One of the clinching arguments for Arizona's tough new law aimed at illegal immigration has been the perception in that state that crime has been rising, and that undocumented workers are largely to blame."

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