Sheriff Joe Arpaio Trial Opens in Phoenix PHOENIX - Letters purporting to offer information about illegal immigrants are among a vast array of evidence to be introduced in the class-action civil rights trial against Sheriff Joe Arpaio and his Maricopa County Sheriff's Office that began on Thursday in Federal District Court here. The elected sheriff and his office are accused of engaging in a pattern of discriminatory policing during large-scale operations known as suppression patrols, unfairly singling out Latinos - including citizens and legal immigrants - for stops, questioning and detention. In one letter to the sheriff, a writer described dark skin as "the look of Mexican illegals," urging the sheriff to go to a particular street corner on the northern edge of this city and "round them all up." Another complained about people speaking Spanish at a fast-food restaurant in Sun City, northwest of here. Yet another grumbled about day laborers gathered at a spot in nearby Mesa, asking when officers would check to see if they were there "under legitimate circumstances." Sheriff Arpaio has repeatedly and vehemently denied the accusations, and legal experts have said that discriminatory intent is hard to prove. In court on Thursday, Tim Casey, a lawyer for the defendants, said: "There are two sides to every story. If the truth were anything like what the plaintiffs are suggesting, it would be a very disturbing picture. Reality, Mr. Casey said, is much different. Race and ethnicity, he went on, have "nothing to do with it." There is much at stake for the civil rights movement. Two of its leading organizations - the American Civil Liberties Union and the Mexican-American Legal Defense and Education Fund - are representing the plaintiffs, and condemning Sheriff Arpaio and his practices is just one of their goals. More broadly, the idea is to highlight the pitfalls of allowing local police officials to play a role in enforcing federal immigration laws. The question was only partly resolved by the Supreme Court last month, when it upheld one aspect of Arizona's immigration law, requiring officers to inquire about the immigration status of the people they stop. It did, however, overturn provisions that would have allowed the officers to arrest people whose only offense was violating federal immigration laws. This trial, and a broader lawsuit filed against Sheriff Arpaio by the Justice Department in May, both focus on potential violations of civil rights. The six plaintiffs named in this litigation, filed nearly five years ago, represent Latinos who were stopped by Maricopa County sheriff's deputies since 2007. Their lawyers will argue that the racially charged letters sent to Sheriff Arpaio led to unlawful enforcement actions. In at least some cases, the crime-suppression patrols took place two or three weeks after letters arrived. Mr. Casey said there was no connection, as it took months to plan the operations. Maricopa County is also named in the litigation; its supervisors failed to stop Sheriff Arpaio, the lawsuit asserts. In court papers, Sheriff Arpaio's own statements were sometimes used to bolster the plaintiffs" arguments, like his description of the raids last year as a "pure program" designed "to go after illegals, not the crime first," and his assertions that speech and appearance, "if they look like they came from another country," were justification for questioning a person's immigration status. As their first witness, the plaintiffs" lawyers called Ralph Taylor, a criminal justice professor at Temple University who has studied the role of race in law enforcement practices. He had been asked to investigate whether people with Hispanic names were more likely to be stopped in traffic by Sheriff Arpaio's deputies. During four hours of testimony, Dr. Taylor concluded that they were, and that stops involving people with Hispanic names lasted, on average, two minutes longer than stops of others. He analyzed about 108,000 stops between January 2007 and October 2009, where the names of roughly 126,000 drivers or passengers had been checked. Tom Liddy, a lawyer for the defendants, questioned Dr. Taylor's analysis, saying it was too narrow to bear much weight. The courtroom, overlooking the atrium at the Sandra Day O'Connor United States Courthouse, was full through much of the day; an overflow crowd of about a dozen people gathered in an upper deck during opening arguments. Outside, protesters gathered, some in prayer, asking the court to determine "once and for all," that Sheriff Arpaio "has committed acts of discrimination and racial profiling," as an organizer put it. On Wednesday, recent high school graduates, organized under the banner "Adiós Arpaio," had fanned out across the heavily Hispanic Alhambra neighborhood here, urging those who were eligible to register to vote. The bench trial, presided over by Judge G. Murray Snow, is scheduled to end on Aug. 2. Sheriff Arpaio, who is 80 and seeking re-election for a sixth term, is likely to testify early next week.