Two House Judiciary subcommittees convened Thursday to examine allegations of unconstitutional immigration enforcement tactics -- and took target practice at Sheriff Joe Arpaio of Arizona, whose controversial methods have been called racist by activists and Democratic lawmakers.

But Arpaio didn't defend himself on Capitol Hill. He did not testify to the committee and he did not attend the joint hearing.

That's because the Maricopa County, Ariz., law enforcement chief wasn't invited, said House Judiciary Committee sources.

"He was not asked or invited to come to this hearing, but he wasn't the direct focus of it," a source within the Judiciary Committee, speaking on condition of anonymity, told FOXNews.com.

The joint hearing by the House Judiciary Committee Immigration, Citizenship, Refugees, Border Security, and International Law Subcommittee and Constitution, Civil Rights, and Civil Liberties Subcommittee Thursday was convened to "focus on wide-ranging allegations of racial profiling in connection with the Immigration and Customs Enforcement's 287 program." It also was used to "examine allegations of unconstitutional policing and immigration enforcement tactics" like those used by Arpaio.

Arpaio's policing methods have drawn widespread criticism from lawmakers and activist groups, like Amnesty International and the ACLU, for allegedly using racial profiling to fight crime in the Southwest. The Arizona sheriff and his deputies have also come under fire for keeping harsh prison conditions and for unfairly targeting illegal immigrants.

Arpaio, who promotes himself as "America's Toughest Sheriff," said he's being unfairly vilified for his approach to law enforcement.

"It's a political witch hunt to use me to stop local law enforcement from enforcing federal laws," Arpaio told FOXNews.com on Thursday, noting that activists who regularly protest his policing hold up signs calling him "Hitler" and "Nazi."

"I've been the sheriff going on 17 years, and I always get re-elected. And all the polls on this issue of immigration support me so it's just a small minority of politicians and activists who accuse me" of mistreating suspects, Arpaio said.

Among the primary concerns during testimony was section 287 of the Immigration and Nationality Act, which was put into law in 1996 as a result of the Illegal Immigration Reform and Immigrant Responsibility Act.

Section 287 authorizes the secretary of Homeland Security to enter into agreements with state and local law enforcement agencies that allow them to identify and detain immigration offenders they encounter during their law enforcement operations.

On Thursday, members of Congress and some of Arpaio's most outspoken critics -- like Mesa, Ariz., Police Chief George Gascon -- met on Capitol Hill to review the impact of federal immigration law on the ability to combat crime by illegal immigrants while also protecting their civil rights.

Gascon did not mention Arpaio by name during his opening testimony, but said the authority handed to local police by federal officials has created an environment in which racial profiling and "constitutional concerns" are setting back the effort to protect the public.

"The impact on local law enforcement in this politically charged environment can be devastating. In some cases, it is setting the police profession back to the 1950s and '60s when police officers were sometimes viewed in minority communities as the enemy," he said.

During Thursday's testimony, Arpaio's absence was noted.

"I want to make clear that he declined to come," said Rep. Zoe Lofgren, D-Calif., chairwoman of the immigration subcommittee.

But when Lofgren was questioned by Rep. Steve King, R-Iowa, about whether the sheriff had been formerly invited, Lofgren said, "No, he said in advance he would not intend to come. In a newspaper article he said he would not come."

Arpaio, who has served as Maricopa County's sheriff since 1992, said he has dedicated the last 30 years working with the federal government, inside the Justice Department and as a Drug Enforcement Administration official, and he would think lawmakers would want to hear about his experience.

"You think they would have called me just to get my expertise -- if nothing else -- about the Mexican-U.S. border. But instead they get one of my biggest critics -- a Mesa police chief who doesn’t like me going into his town arrested illegals -- and a couple other people," he said.

"These congressmen never had the courtesy to ask me to speak," he said.

Arpaio also defended his policing methods, saying they are both constitutional and effective in lowering crime rates.

"We investigated 147,000 people booked into our jail under 287. And 23,000 murderers all the way down we proved are illegal so they can not get back on the street. That's why crime has gone down in this area," he said.

The sheriff said he has invited congressional critics to come to Arizona to observe his operations, but so far has got no response.

"I'm just enforcing the law that I took an oath of office to enforce. And nobody's going to deter me or scare me away," he said. "They can go after me all they want, but I'm very comfortable the way I run my operation."