The American Civil Liberties Union and the ACLU of South Carolina asked a federal court on Friday to allow them to become involved in a lawsuit about the state's controversial voter identification law.

The U.S. Department of Justice blocked the law in December. Earlier this month, South Carolina again sought approval by filing suit in U.S. District Court in Washington, D.C.

The law, passed last year, would require residents to present government-issued photo ID at the polls. South Carolina officials say it would prevent voter fraud, while critics say it would suppress turnout among poor, rural and minority voters. Those opposed to the law also note that the state has failed to show a voter fraud problem exists.

The ACLU's motion Friday would add new defendants to the suit, including three registered voters who would not be allowed to vote under the new law because they do not have acceptable ID. Family Unit, a Sumter nonprofit group that helps people register to vote, also would be added to the suit.

"Our elected officials should make it easier for South Carolinians to exercise their right to vote, not put more barriers in their way," said Victoria Middleton, executive director of the ACLU of South Carolina.

The state will argue before a three-judge panel in Washington that it should be able to keep the ID law, which has not been enacted. If the state loses there, the appeal could go directly to the U.S. Supreme Court. The state's appeal could challenge the Voting Rights Act, a 1965 law requiring the federal government to approve any changes to voting laws in South Carolina and other mostly Southeastern states with histories of discriminating against minority voters.

The litigation could cost South Carolina more than $1 million, The Post and Courier reported last month.

S.C. Attorney General Alan Wilson has said "that over 900 deceased people appear to have 'voted' in recent elections in South Carolina."

A State Law Enforcement Division investigation of alleged voter fraud is "still ongoing," SLED spokeswoman Kathryn Richardson said Friday.

"I don't have a time frame" for its completion, she said.

The State Election Commission, however, released findings of its own probe on Thursday. The Commission reviewed about one-fifth of the allegedly deceased voters' records.

"In more than 95 percent of the cases we examined, there is no indication that votes were cast fraudulently," Director Marci Andino said. Records were "insufficient to make a determination" in the remaining 5 percent, the commission said.

Most of the problems stemmed from clerical errors, according to the commission.