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The attorney defending Texas over its controversial voter ID law faced a tough room during closing arguments Friday, as federal judges grilled him and one claimed the record shows the law puts a "disproportionate" burden on minorities.

The judges assumed a skeptical tone as they wrapped up five days of trial, suggesting the state may face a heavy lift in persuading the three-judge panel to overrule the Justice Department -- which concluded in March that the Texas law requiring voters to have certain ID to cast a ballot is illegal by disproportionately disenfranchising Hispanic voters.

At the beginning of session Friday, Texas' attorney John Hughes said his closing arguments would last 20 minutes. But the argument turned into a back-and-forth lasting more than an hour, as judges frequently interrupted Hughes to pose various questions. Hughes repeatedly rejected the notion that the Lone Star State's voter ID law, passed last year, would affect minorities any differently than it would affect white voters.

"(It) does not deny or abridge the right to vote on account of race or color," Hughes told the judges.

He repeatedly said "social science" presented to the court, particularly past surveys of voters, shows that voter ID laws don't stop eligible voters from going to the polls. He noted that the Justice Department's "own expert" in the trial, Harvard University professor Stephen Ansolabehere, analyzed data from states with voter ID laws and wrote an article in 2009 which said "the actual denials of the vote in these two surveys suggest that photo-ID laws may prevent almost no one from voting."

But Judge David Tatel, from the U.S. Court of Appeals for the District of Columbia, jumped in to say Ansolabehere testified this week that "his research shows a different situation in Texas" than in the other states that formed the basis for his 2009 article.

And while in response Hughes said Ansolabehere "admitted he has no opinion on the ultimate effect of" the Texas voter ID law, U.S. District Judge Rosemary Collyer said that "doesn't undercut his evidence that there is an uneven influence on the numbers of minorities in Texas who do not possess the requisite identification."

Under the Voting Rights Act of 1965, the Justice Department can block some states from making changes to their voting laws -- unless a federal court rules otherwise.

Justice Department attorney Matthew Colangelo, in a closing argument that was much shorter and less heated than Hughes', told the judges the Texas voter ID law is "exactly the type of law" Congress had in mind when it passed the Voting Rights Act to end "discriminatory practices."

In a report submitted to the judges before the trial began Monday, Ansolabehere, a political science professor, said he determined that 11 percent of white registered voters in Texas don't have a state ID, 18 percent of Hispanic registered voters don't have a state ID, and 21 percent of black registered voters don't have a state ID.

Hughes called Ansolabehere's conclusions "hopelessly flawed" because there are "categorical problems" with the data he used for his analysis.

Hughes noted that Ansolabehere did not look at whether voters he declared as lacking valid ID actually possessed federal identification acceptable under the Texas voter ID law, such as a U.S. passport. Hughes also said demographic data provided to Ansolabehere by a liberal-leaning firm was unreliable, with University of Texas professor Daron Shaw testifying that one-third of 600 voters identified as black were not in fact black.

Questioning the Justice Department's assertions that 1.5 million people could be impacted by the Texas voter ID law, Hughes said "if that were remotely true the courtroom would be filled" with people opposing the law.

In a statement Friday, the chairman of the House Judiciary Committee, Lamar Smith, said that -- after a week of trial -- it is "clear that the Justice Department's case is based on biased and flawed evidence."

"The administration's case is so weak that it crumbles under the pressure of facts," said Smith, a Republican from Texas. "The Justice Department has not made its case to the court or the American people."

But as the judges said and as Hughes acknowledged, "Texas has the burden" to prove that the voter ID law is not discriminatory. The Justice Department does not have to prove that the law is in fact discriminatory.

"Technically, the government didn't need to do anything" during the trial, Tatel said.

And Tatel noted that professor Shaw, a witness called by the state of Texas, found that there was in fact a "subset of registered voters that lack" the required ID. Tatel said that while "significant" portions of both minority and white voters don't have the necessary ID, "the economic burden of obtaining it" is "what creates the retrogressive" effect. He said the record shows minorities in Texas disproportionately lack their own cars and live up to 120 miles away from the closest ID office.

Colangelo said 80 of 200 counties in Texas don't have any ID office, which he said means minority voters would face "tremendous burdens" in obtaining even free IDs offered by the state.

In addition, U.S. District Court Judge Robert Wilkins cited federal law banning subpoenas to people who live more than 100 miles away because, according to the law, that is "unduly burdensome." He asked Hughes how it can be "unduly burdensome" for a Texan under subpoena to have to drive more than 100 miles but it's not "unduly burdensome" for a Texan to have to drive more than 100 miles to get a state ID.

Hughes said some Texans "select to live in a place" that requires them to travel long distances "to do any number of things."

"It's just a reality of life that they have to drive long distances," he said.

He told the judges that focusing on that point "puts us to an impossible burden" in proving Texas' case, saying the legal burden keeps "shifting, shifting, shifting." He said the Justice Department can't prove a disparity among those who lack the ID required to vote under the Texas law, so the department is now changing its argument to focus on the economic burden it presents.

He said all Texas needs to prove to win its case is that the voter ID law will have no impact on voting in Texas, insisting past research and other evidence "is overwhelming and it satisfies our burden."

Much discussion during Friday's arguments centered around whether racially motivated discrimination needed to be part of the purpose of the Texas voter ID law for it to be found illegal.

Colangelo said the law was passed with a "backdrop" of "huge, explosive" growth in the state's Hispanic and Latino population over the past decade.

Wilkins posed a hypothetical situation to Hughes: If the Texas legislature passed a law requiring voters to "satisfactorily" recite the Pledge of Allegiance before voting, and the only purpose of that requirement was for "people to be patriotic," would that be legal under the Voting Rights Act? Wilkins said Hughes should assume a "disproportionate" number of non-English speakers would have trouble reciting the Pledge of Allegiance.

Hughes responded: "That would establish a (Voting Rights Act) violation, but those facts are very different than this case."

The judges are expected to rule on the Texas voter ID case by the end of August. Some observers believe the case -- and therefore the Voting Rights Act -- could become a matter for the U.S. Supreme Court to decide.

Fox News' Madison Martin contributed to this report.