Election board officials assured skeptical D.C. City Council members yesterday that they would take adequate measures to detect and prosecute anyone who fraudulently votes without proof of registration in the Nov. 2 general election.

Election board Chairman Albert J. Beveridge III said that board officials will check each of the affidavits signed by people whose names do not appear on voter rolls and who do not have their registration cards.

The board ruled on Monday that such people can vote as long as they provide some identification and sign an affidavit that they are registered voters.

Beveridge told the D.C. City Council's government operations committee that if significant numbers of those affidavits turn out to be fraudulent, the election could be open to a challenge.

"In practical terms you've got to have thousands of people" voting fraudulently before a serious challenge could be brought, he said. He added that the board will "certainly take steps to prosecute" anyone it believes has voted fraudulently.

Beveridge said after the meeting that a challenge would be likely only if the number of ballots cast by voters who turn out to be not properly registered is enough to change the results of a particular race.

However, council member Betty Ann Kane (D-At Large) said she was concerned that even if a few of the affidavits prove false, the ballots cast fraudulently will have already been counted.

"The only follow-up will be prosecution. There is no way to uncount that vote," Kane said.

Election board officials agreed.

Council members and an assistant corporation counsel also expressed concern about the legality of the board's affidavit plan.

Earlier this week council member William R. Spaulding (D-Ward 5) asked the city's corporation counsel for a legal opinion on the board's decision to allow voters with no other proof of registration to cast regular ballots if they sign the required affidavit.

Yesterday, assistant corporation counsel Inez Smith Reid said her office has not finished its opinion, but she raised several concerns about the procedure, including whether the board has statutory authority to allow people to vote in this manner.

Reid also said her office will study whether the procedure is "illegally subjective" because it gives too much authority to precinct workers who have the final say in deciding whether voters without registration cards and whose names are not on voter rolls have supplied enough evidence to prove that they are registered.

She said that her office must determine whether the procedure violates another provision of election law that prohibits any new registrations from being filed within 30 days of an election.

Spaulding and other critics say the board's new procedure may amount to on-site registration on election day and therefore may be illegal.

Reid said the corporation counsel's office should issue a written opinion some time this week.

Council member Nadine P. Winter (D-Ward 6) said she was concerned that some voters who sign these affidavits believing that they are indeed registered, will be left open to prosecution if later afterwards the board can find no record of them in its files.

"I'm concerned about all this court action and possible court costs for, say, Mary Jones who's already on public assistance," Winter told Beveridge at one point.

Beveridge told the council members that precinct workers, and even candidates' poll watchers, would have the right to object to a voter casting a regular ballot if his or her name is not on the voter rolls. In such cases, he said, those voters would have to cast special challenge ballots.

But Beveridge added, "If somebody wants to cheat, they can cheat. We have a very easy registration system."