PHOENIX » For six years, the self-proclaimed toughest sheriff in America has vehemently denied allegations that his deputies racially profile Latinos in his trademark immigration patrols.

Joe Arpaio would dismiss his critics in his signature brash style at countless news conferences and in numerous appearances on television.

Now, the sheriff in Arizona’s most populous county will have to convince a federal judge who is presiding over a lawsuit that heads to trial today and is expected to last until early August.

The plaintiffs say Arpaio’s officers based some traffic stops on the race of Hispanics who were in vehicles, had no probable cause to pull them over and made the stops so they could inquire about their immigration status.

“He is not free to say whatever he wants,” said Dan Pochoda, a lawyer for the American Civil Liberties Union of Arizona, one of the groups that has pushed the lawsuit against Arpaio.

“He will be called as a witness in our case,” Pochoda said. “He will not have control over the flow of information, and he is not the final arbiter.”

The plaintiffs aren’t seeking money damages and instead are seeking a declaration that Arpaio’s office racially profiles and an order that requires it to make changes to prevent what they said is discriminatory policing.

If Arpaio loses the civil case, he won’t face jail time or fines.

Arpaio declined to comment, and his lead attorney, Tim Casey, didn’t return a call seeking comment Wednesday.

But at a late June hearing, Casey said the sheriff wanted the trial so he could prove his critics wrong and remove the stigma that the racial profiling allegation carries. “What we want is resolution,” Casey said.

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 bellwether for a similar yet broader civil rights lawsuit filed against Arpaio in May by the U.S. Department of Justice.

That lawsuit makes many of the same racial profiling allegations, but goes further to say that Arpaio’s office retaliated against its critics, punished Latino jail inmates with limited English skills for speaking Spanish and failed to adequately investigate a large number of sex-crimes cases. No trial date in that case has been set.

Arpaio has said the DOJ lawsuit is a politically motivated attack by the Obama administration as a way to court Latino voters in a presidential election year. DOJ officials say the department began its initial civil rights inquiry of Arpaio’s office during the Bush administration and notified the sheriff of its formal investigation a few months after Obama took office.

Arpaio has staked his reputation on immigration enforcement and, in turn, won support and financial contributors from people across the country who helped him build a $4 million campaign war chest.

The patrols have brought allegations that Arpaio himself ordered some of them not based on reports of crime but letters from Arizonans who complained about people with dark skin congregating in an area or speaking Spanish.

Some of the people who filed the lawsuit were stopped by Arpaio’s deputies in regular patrols, while others were stopped in his special immigration patrols known as “sweeps.”

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.

Illegal 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.

Arpaio has repeatedly said people who are pulled over in his patrols were approached because deputies had probable cause to believe they had committed crimes and that it was only afterward that officers found that many of them were illegal immigrants.

U.S. District Judge Murray Snow has issued rulings against Arpaio earlier in the case. In December, he barred Arpaio’s deputies who are enforcing Arizona’s 2005 immigrant smuggling law from detaining people based solely on the suspicion that they’re in the country illegally. Arpaio has appealed that decision.

Without ruling on the ultimate question of whether Arpaio’s deputies racially profile Latinos, the judge ruled in December that a reasonable trier of fact could interpret some of Arpaio’s public statements as endorsing racial profiling.

As he considers the case, Snow said, he may assume that the records that Arpaio’s office has acknowledged destroying in the case could have included documents such as citizen complaints, some of which could have been racially charged and didn’t allege criminal activity.

Still, Snow reminded plaintiffs’ attorneys what they need to prove to make their claim of systematic discrimination. At a hearing in March, the judge told them that in order to back up the racial profiling allegations, they must show that Arpaio’s office had a policy that was intentionally discriminatory.

The judge said “even if I accept as true the premise that there was an illegal search or an illegal stop that was without probable cause, 10 or 11 stops by different officers over the course of three years doesn’t do a lot towards establishing a policy and procedure.”

The plaintiffs’ attorneys say they plan to prove systematic discrimination, in part, by focusing on their allegation that Arpaio launched some patrols based on racially charged citizen complaints that alleged no actual crimes.

Separate from the two lawsuits that allege racial profiling, a federal grand jury has been investigating Arpaio’s office on criminal abuse-of-power allegations since at least December 2009 and is specifically examining the investigative work of the sheriff’s anti-public corruption squad.