Phoenix (CNN) -- Attorneys gave opening statements Thursday in a civil trial accusing an Arizona sheriff -- who bills himself as "America's toughest" -- and his department of racial discrimination against Latinos.
The American Civil Liberties Union of Arizona and other attorneys are representing Hispanics in a class-action lawsuit accusing Maricopa County Sheriff Joe Arpaio of civil rights and constitutional violations. The bench trial is being held in the U.S. District Court in Phoenix.
In his opening remarks, Stanley Young, an attorney for the plaintiffs, told the judge that Arpaio and his department violated "the fundamental value of equal protection under the law" through a "policy of racial discrimination and mistreatment of Hispanics."
Tim Casey, an attorney for the sheriff, told the court that "there is no evidence that race or ethnicity played a factor" in the detention of the five named plaintiffs.
"Ethnic constituency of the neighborhood plays no role" in the Maricopa County Sheriff's Department's selection of neighborhoods for saturation patrols, Casey said in court.
Arpaio is expected to appear in court to testify early next week.
Outside the federal courthouse, Arpaio critics demonstrated and carried placards stating, "No justice. No peace. No racist police."
Among the first witnesses Thursday was Ralph Taylor, a Temple University professor of criminal justice. Taylor testified that he did a statistical analysis that shows Hispanics are more likely to be checked for immigration status during saturation patrols than non-Hispanics are.
Arpaio is nationally known for his tough stances against illegal immigration, but critics have said for years that his approach has created a system of racial profiling.
The U.S. Justice Department has also filed a civil rights lawsuit against him, but Thursday's trial is for a different lawsuit brought by Hispanics who say they were discriminated against.
The class-action lawsuit, filed in 2007, claims that Arpaio and the Maricopa County Sheriff's Office "launched a series of massive so-called 'crime suppression sweeps' that show a law enforcement agency operating well beyond the bounds of the law."
The plaintiffs are also being represented by the law firm Covington & Burling.
"They're never easy cases, there's no smoking gun," ACLU of Arizona legal director Dan Pochoda said of the class-action suit. "We don't expect a memo in the file that says let's get these people solely because they're Hispanic. We believe the evidence will demonstrate that is indeed effectively what was done."
Arpaio and his attorneys declined to comment before the trial.
In a CNN interview last year, Arpaio said his department would continue to pursue illegal immigrants.
"I know I'm doing the right thing. I'm not going to surrender by those little small groups, people that don't like what I'm doing. You think I'm going to surrender? It'll never happen," the sheriff said.
The lawsuit charges that the sheriff's office "unlawfully instituted a pattern and practice of targeting Latino drivers and passengers in Maricopa County during traffic stops," the ACLU said in a statement.
The sheriff's tactics violate the Equal Protection Act by discriminating by race and result in prolonged detentions that violate protections against unreasonable searches, the ACLU said.
The office's "pattern and practice of racial profiling goes beyond these sweeps to include widespread, day-to-day targeting and mistreatment of persons who appear to be Latino," the lawsuit states.
Among the plaintiffs is Manuel Ortega Melendres, a visitor to Arizona who possessed a valid visa. In September 2007, he was arrested after the car he was riding in was pulled over by Maricopa County deputies. The lawsuit alleges that Melendres showed the officers his identification but was nonetheless treated roughly and arrested. He sat in a cell for hours before a federal immigration agent confirmed that his documents were in order.
As a result of his ordeal, Melendres was left "frightened to walk on the street or be seen in public in Maricopa County because he fears that the sheriff's officers will come and arrest him again because he is Latino and does not speak English," the lawsuit states.
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CNN's Mariano Castillo, Natalie Brunell and Chuck Conder contributed to this report. Wian and Conder reported from Phoenix.