Caption:NOGALES, AZ - DECEMBER 07: A border patrol agent and Gitta, a drug-sniffing German shepherd, work a checkpoint on December 7, 2010 north of Nogales, Arizona. The checkpoint falls in the Tucson sector of the U.S.- Mexico border and is considered the most heavily trafficked by illegal immigrants and drug smugglers in the United States. (Photo by John Moore/Getty Images)
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