PHOENIX -- Offensive letters, tearful personal stories and reams of statistics have been shared as plaintiffs' lawyers rested their case Tuesday in a racial profiling lawsuit against an Arizona sheriff and his department.

But legal experts say the group of Latinos who brought the civil case against Maricopa County's Joe Arpaio, known by his supporters as "America's Toughest Sheriff," have a high bar to clear to convince a judge that there was systematic discrimination in the agency.

"These cases are difficult to bring and difficult to win under the best circumstances," said David A. Harris, a law professor at the University of Pittsburgh who studies racial profiling and wrote a book on the subject.

Arpaio has repeatedly denied charges that his department discriminates against Latinos, saying his deputies only stop people when they think a crime has been committed.

But plaintiffs say deputies pulled over some vehicles only to make immigration status checks during regular traffic patrols and the sheriff's special "immigration sweeps."

Dan Pochoda, a lawyer for the American Civil Liberties Union of Arizona, pressing the case on behalf of the plaintiffs, said his side is relying on circumstantial evidence.

"There is rarely a smoking gun in these cases," Pochoda said.

Arpaio's office and top attorney Tim Casey declined to comment Tuesday. But throughout the trial the defendants have disputed evidence at all turns and pointed out that officers have received training in preventing racial profiling.

Testimony is expected to wrap this week, and U.S. District Judge Murray Snow will decide the case.

Experts say it's not enough for plaintiffs' lawyers to show that a person or a group of people were discriminated against by sheriff's deputies. To prove systematic racial profiling, lawyers must present multiple layers of supporting evidence, such as testimony and statistics, Harris said. He added that such an approach makes it harder to dismiss claims as isolated.

To that effort, plaintiffs' lawyers have presented people who broke down in tears as they described encounters with authorities, saying they were pulled over because they were Hispanic and officers wanted to check their immigration status, not because they had committed an infraction.

Attorneys for Arpaio and the department disputed such characterizations, typically working to show that officers had probable cause to stop the drivers based on a traffic violation.

Plaintiffs' lawyers also presented statistics to show that Latinos are more likely to be stopped on days of immigration patrols. And they criticized the department saying its safeguards against discriminatory policing are flimsy. They also showed emails containing offensive jokes about people of Mexican heritage that were circulated among sheriff's department employees, including a supervisor in Arpaio's immigrant smuggling squad.

The plaintiffs also have accused Arpaio of launching some patrols based on letters from county residents complaining that dark-skinned people were congregating or speaking Spanish, but did not allege any criminal activity.

Defense lawyers disputed the statistical findings and said that officers who circulated offensive jokes were disciplined. They also denied that the complaint letters prompted patrols with a discriminatory motive.

Also, Arpaio's lawyers asked Snow for a dismissal, arguing in part that there was no testimony offered to prove plaintiffs' claims that racial profiling safeguards were inadequate.

The judge denied the request and said the trial will continue.

The lawsuit marks the first case in which the sheriff's office has been accused of systematically racially profiling Latinos and will serve as a precursor for a similar yet broader civil rights lawsuit filed against Arpaio and his agency by the U.S. Justice Department.

Maricopa County officials say a suit making a similar profiling allegation against the sheriff's office was settled last year without an admission of wrongdoing.

The plaintiffs in the case currently before Judge Snow aren't seeking money damages, they are seeking a declaration that Arpaio's office racially profiles and an order requiring policy changes. If Arpaio loses the case, he won't face jail time or fines.

If he wins, it will severely undercut the upcoming federal case against him that makes similar allegations and also focuses on the special immigration patrols.

During the sweeps, deputies flood an area of a city - in some cases, heavily Latino areas - over several days to seek out traffic violators and arrest other offenders. Undocumented immigrants accounted for 57 percent of the 1,500 people arrested in the 20 sweeps conducted by his office since January 2008, according to figures provided by Arpaio's office, which hasn't conducted any of the special patrols since October.

Gabriel J. Chin, a University of Davis law professor whose specialty includes race and the law, said discrimination cases are hard to prove because there's always an alternative explanation presented. But Chin said alternative explanations can work against an agency.

"At some point, you are asking the finder of fact to accept a lot of coincidences," Chin said.

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  • Maricopa County Employees Call Latinos Derogatory Names

    Jail employees frequently refer to Latinos as "wetbacks," "Mexican bitches," and "stupid Mexicans," according to the lawsuit. An email that included a photography of a Chihahua dressed in swimming gear with the caption "A Rare Photo of a Mexican Navy Seal" was widely distributed by sheriff's office supervisors.

  • Officers Mistreat Latinos In Routine Traffic Enforcement

    The lawsuit recounts how a Latina woman who was five-months pregnant and a U.S. citizen was stopped as she pulled into the driveway. "After she exited her car, the officer then insisted that she sit on the hood of the car. When she refused, the officer grabbed her arms, puled them behind her back, and slammed her, stomach first, into the vehicle three times. He then dragged her to the patrol car and shoved her into the backseat," reads the complaint. She was cited for failure to provide identification, which was later changed to failure to provide proof of insurance. The issue was resolved when the woman proved she had insurance to a court. In yet another case, two officers followed a Latina U.S. citizen a quarter of a mile to her home without flashing their lights. When she arrived home, they insisted that she stay in the car. The reason for the stop was a "non-functioning license plate light." After she tried to enter her home, officers took her to the ground, kneed her in the back and handcuffed her. She was brought to a Maricopa County Sheriff's Office (MCSO) substation and cited for "disorderly conduct," which was later dismissed, according to the lawsuit.

  • Latinos Are Indiscriminately Detained In Immigration Raids

    A Latina born in the United States was taken into custody for four hours in a raid to determine her immigration status. Arpaio was quoted in response, "That's just normal police work. You sometimes take people in for probable cause for questioning and they're released." The suit notes that the reason for her detainment -- being Latina and present during a raid -- were insufficient.

  • Arpaio And MCSO Staff Foster Discrimination Against Latinos

    Arpaio received a letter reading, "If you have dark skin, then you have dark skin. Unfortunately, that is the look of the Mexican illegals who are here illegally. ... I'm begging you to come over ... and round them all up." The sheriff labeled this as "intelligence" and forwarded to his deputy chief of enforcement operations for someone to "handle this." Upon receiving a letter backing the policy of "stopping Mexicans to make sure they are legal," he sent a letter of appreciation to the authors and kept three copies for himself, according to the lawsuit. An email circulated among MCSO staff had an image of a fake driver's license from "Mexifornia" and listed the driver's class as "illegal alien."

  • MCSO Employees Fail To Provide Assistance To Prisoners With Limited English

    The failure to provide adequate language assistance caused some female Latina prisoners to remain with sheets or pants soiled from menstruation, alleges the suit. Others have allegedly been put in solitary confinement for "extended periods of time" for not understanding a command in English.

  • MCSO Arrests Arpaio Critics Expressing Their First Amendment Rights

    The suit claims on multiple occasions that people were arrested for merely applauding against the office's immigration policies. The judge presiding over the case of the arrestees found that the deputy who made the arrest "believes it is his role to make uncomfortable anyone who express[es] views that disagree with the sheriff" and that he had "trampled" over the First Amendment. The court acquitted them.