A federal judge on Thursday ordered Maryland to allow disabled voters in November to fill out absentee ballots online before printing and mailing them to election officials.

The National Federation of the Blind and three individuals who are deaf, blind or palsied sued the Maryland State Board of Elections to activate the computer ballot-marking tool, which the board developed with help from the federation.

The tool was available to absentee voters in the state’s 2012 primary elections and to overseas voters that November. However, an improved version that makes it easier for people with disabilities to use the tool was not certified by the election board for use this fall.

The lawsuit was opposed by the American Council of the Blind of Maryland; two organizations that work to promote election security, VerifiedVoting.org and SAVEourVotes.org; and three individuals, with different disabilities, who say the new software is still not accessible to them and is vulnerable to being hacked.

In a 33-page opinion, U.S. District Judge Richard D. Bennett, sitting in Baltimore, said the board’s decision denied disabled plaintiffs “meaningful access to the State’s absentee ballot voting program as mandated by the Americans with Disabilities Act and the Rehabilitation Act.”

Bennett wrote that “earlier uses of the tool appear to have been uneventful, and there has been no evidence of security breaches connected to that use.”

In Maryland, anyone can vote by absentee ballot. People who need assistance can submit a form to have someone help them fill out their ballots before they are signed and returned.

The online ballot-marking tool allows disabled voters to use computer technology — such as a mouse or voice-recognition software — to mark ballots privately and independently, the plaintiffs in the lawsuit said. About 5 percent of Maryland voters cast absentee ballots, and a fraction of them are disabled.

“This ruling is a victory for Maryland voters with disabilities and puts election officials across the nation on notice that full and equal access to voting includes access to absentee ballots, as well as to the voting equipment used at polling places,” Mark Riccobono, president of the National Federation of the Blind and the husband of one of the plaintiffs, said in a statement.

But opponents said computer “spyware” could be used to reveal an absentee voter’s choices to a third party. They also said the state election board’s computer server could be hacked while a completed ballot was being prepared for printing, giving the hacker information on a voter’s choices.

Pamela Smith, president of VerifiedVoting, said the tool “recklessly ignores important privacy and security risks. . . . Forcing this tool to be available in its current state severely compromises voter privacy and may call the results of Maryland elections into question.”

Nikki Baines Charlson, deputy administrator of the state election board, said the board is reviewing the opinion but will be ready to activate the tool once absentee ballots are sent to voters Sept. 19. “It’s not online voting,” Charlson said. “It’s a way to mark your ballot. It’s a sophisticated pencil.”

David R. Paulson, a spokesman for state Attorney General Douglas F. Gansler, said the office is reviewing the opinion, and he declined to comment.

The ruling comes as a partisan battle over ballot access rages in many states, with Democrats generally seeking expanded access to protect voters’ rights and Republicans generally seeking limits to protect against voter fraud.

Bennett’s ruling noted that spyware and hacking pose some security risk, but he also said a computer security firm — approved by an outside auditor who was retained by the election board — found the tool to be secure. He wrote that an expert called by plaintiffs testified that the tool posed “no additional risks that did not exist in other methods already available to voters.”

A 2013 state law required the five-member election board to certify the ballot-marking tool by a supermajority, or fourth-fifths, vote. The board’s three Democrats voted for certification at a July 10 meeting. One Republican, Charles Thomann was absent, and the other, David J. McManus Jr., voted no.

On Thursday, Thomann said he remained uncertain as to how he would have voted, and he deferred to McManus, saying, “I’ll agree with whatever he says.” McManus declined to comment.

A partial survey of states by the election board’s staff found that only Alaska and Delaware were making an online ballot-marking tool available to voters with disabilities this year, the judge wrote, although several states do so for some overseas voters.

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