HARRISBURG - In closing arguments in the closely watched hearing on the fate of Pennsylvania's controversial voter identification law, a lawyer for the law's opponents said as many as one million people may be prevented from casting ballots in November.

Commonwealth attorney Patrick Cawley, however, countered that "the vast majority of voters will have no problem" as a result of the act, which its backers say is meant to prevent fraud. "We would like to try to err on the side of protecting voters," he said.

The arguments wrapped up a seven-day hearing in Commonwealth Court in which a number of interest groups seek an injunction to stop the five-month-old voter ID law from taking effect. They contend it creates an unnecessary barrier to voting and is designed reduce turnout among poor and minorities, two largely Democratic constituent groups. Proponents of the law, passed by the Republican-controlled legislature, contend it is needed to prevent fraud.

Judge Robert E. Simpson said he would issue his ruling the week of Aug. 13. Both sides have said they will appeal to the state Supreme Court if they lose.

On May 1, the American Civil Liberties Union, along with voter and civil rights groups, sued on behalf of a group of petitioners who said they would not be able to vote because they faced impediments to getting an ID.

Vic Walczak, legal director of the ACLU of Pennsylvania, argued that the law would disenfranchise legitimate voters while serving no purpose because the commonwealth has agreed there is no evidence of in-person voter fraud in past elections.

"There are registered voters who will be unable to vote under this law," Walczak said. "The commonwealth has not assured us that every one of the petitioners can vote, and that's the tip of the iceberg."

But Cawley, who is senior deputy attorney general, said the opponents failed to meet the burden of proof that the law imposes "a burden on any one group of voters."

"This is a neutral, nondiscriminatory statute," Cawley said.

Under the law, one of the strictest in the nation, voters must present a valid Pennsylvania driver's license or a nondriver's identification card or a military, college, or government ID that has an expiration date. The law also allows nursing homes to issue their own IDs.

By the end of the month, the Department of State says, it will issue a photo identification card through the Pennsylvania Department of Transportation designed for those unable to secure valid ID any other way. Applicants need only provide two proofs of residence, but they must first show they have exhausted all other avenues.

"If there is anything that came through loud and clear, it's that not everybody in this country has ID and not everybody without ID has the means to get it," Walczak said.

He said regardless of the numbers of ID-less voters - estimates range from several hundred thousand to more than a million - the state had not provided assurances that everyone will have an ID on Election Day.

Cawley countered that "the petitioners did not prove any widespread voter disenfranchisement" in other states that had voter ID laws."

"It hasn't happened elsewhere and won't happen here," he said.

Over the course of the hearing, the opponents presented 14 witnesses, including experts in voter fraud and statistics, elections officials in Pittsburgh and Philadelphia, and individuals who said they would be unable to vote.

Four "testers" who visited PennDot offices to determine whether staffers were prepared to handle the influx of ID seekers testified that office hours were limited in many places and that employees were ill-prepared or gave out misinformation.

Cawley sought to discredit their testimony as biased because the witnesses all acknowledged that they opposed the law.

Walczak raised the specter of political motivation driving the law here and in other states, suggesting there was "illicit interest" in passing the legislation.

He played the widely disseminated clip of House Majority Leader Mike Turzai (R., Allegheny) telling GOP supporters in June that the voter ID would "allow Mitt Romney" to win Pennsylvania.

"That tape suggests in terms of intent and effect there is partisan gain at issue," Walczak said.

Secretary of the Commonwealth Carol Aichele was the only witness to appear on behalf of the state. She defended the law, saying the state was doing everything in its power to spread the word about the new law and ensure that all eligible voters would be able to cast ballots in November.

Contact Amy Worden at 717-783-2584, aworden@phillynews.com, or follow @inkyamy on Twitter.