Justice Dept. Seeks to Join Suit Over 117,000 Purged Brooklyn Voters

The Justice Department announced on Thursday that it had filed a motion to join a lawsuit against the New York City Board of Elections, alleging that the board’s Brooklyn office violated federal voter registration law by erasing more than 117,000 Brooklyn voters from the rolls before the primary election simply because they had not voted in previous elections.

The filing accused the board of failing to take several steps that are normally required before a voter’s name is removed, and also raised concerns about how the board oversaw the Brooklyn office’s handling of the voter rolls.

The petition by the Justice Department to intervene in a lawsuit filed in November by Common Cause New York, a good-government organization, lends significant muscle to an effort to hold the agency responsible for a chaotic Primary Day in April, when many voters in Brooklyn were surprised and infuriated to learn that their voter registrations had been canceled.

With the filing on Thursday, the Justice Department becomes perhaps the most potent of the government players trying to force changes at the board. The city comptroller, Scott M. Stringer, and the state attorney general, Eric T. Schneiderman, both opened inquiries into the board’s procedures after its bungled Primary Day performance, and Mayor Bill de Blasio has called for spending $20 million to improve city voting procedures.

The fallout has already affected one Board of Elections employee: the board’s chief clerk in Brooklyn, Diane Haslett-Rudiano, who was suspended shortly after the primary election.

The Justice Department’s legal complaint describes how Ms. Haslett-Rudiano’s attempt to perform a routine winnowing of the Brooklyn voter rolls went awry: Starting in late 2013 or early 2014, it says, staff members scrubbed the office’s voter database for people who had not voted since 2008, neglecting to check whether the voters had died or moved away, as is required by federal law. And more than 4,100 of the flagged voters had, in fact, voted at least once since 2008, according to the complaint.

Ultimately, more than 122,000 voters were flagged for removal, according to the complaint. About 4,470 responded to mailed notices informing them they were about to be purged, leaving about 117,000 voters whom the board went on to remove from the rolls.

Yet another problem followed, the complaint said: The Brooklyn voter database did not sync properly with the state voter database for about six months, leading voters who looked up their registration status in the state database to believe that they were still registered, even though their names had been erased from the Brooklyn list.

Still, the board’s director, Michael J. Ryan, insisted soon after the election that no voters had been disenfranchised, through he pledged to cooperate with the investigations.

“Federal law demands careful maintenance of the voter rolls to ensure lists are kept accurate, without unjustifiably and unlawfully purging eligible citizens,” Vanita Gupta, the head of the Justice Department’s civil rights division, said in a statement in submitting the complaint. “The department appreciates the continued cooperation of the New York City Board of Elections, including proactive steps taken to start remedying violations that have occurred — but more is necessary to reach full compliance with the law.”

According to the complaint, also submitted by Robert L. Capers, the United States attorney for the Eastern District of New York, Mr. Ryan has testified that the board is moving toward reinstating the approximately 117,000 people removed from the rolls.

“We are reviewing the issues raised in this litigation and will work with the Department of Justice toward a resolution,” said Nick Paolucci, a spokesman for the city’s Law Department, which is representing the Board of Elections in the lawsuit.

A version of this article appears in print on , on Page A23 of the New York edition with the headline: Justice Department Seeks to Join Lawsuit Over the Purge of 117,000 Brooklyn Voters. Order Reprints | Today’s Paper | Subscribe