Slidell voters in the 1500 block of Englewood Drive didn’t get to vote in the City Council District E primary on April 5 because a mapping error mistakenly placed them in District C on the voter registration rolls, St. Tammany Parish Registrar of Voters Dwayne Wall confirmed Tuesday.

The municipal elections were the first in Slidell since reapportionment, Wall said, and the mistake was the result of human error.

It came to his attention when District E candidate Pete O’Connell called the Monday after the election to find out why two voters who contacted him had not been able to vote in his race.

Wall said the mistake potentially affected 44 voters, a substantial number for an election in which only 648 voters cast ballots. The registrar’s office sent letters to them April 11 informing them of the error and apologizing for any inconvenience it may have caused.

O’Connell, who got 205 votes in the primary, will face off in a May 3 runoff against incumbent Councilman Sam Caruso, who got 309 votes.

Candidates have a nine-day window in which to challenge the results of an election, according to Meg Casper, spokeswoman for Louisiana Secretary of State Tom Schedler. That period ended April 14, she said.

Caruso said he learned of the problem about 40 minutes before the deadline elapsed and chose not to challenge the results. But he pointed out that he captured 70 percent of the votes in the affected area — his own neighborhood — and missed winning the primary outright by slightly more than 2 percentage points.

The worst part, Caruso said, “is simply the deprivation of these people’s right to vote. It seems to me that’s even worse than what happened to us (the candidates).’’

“In a small council district, the impact of voters from 44 households being denied the opportunity to cast ballots for the candidate of their choice could have swayed the election outcome,’’ said James Hartman, O’Connell’s campaign consultant. “Obviously, we understand that mistakes happen and that technology fails, and we’re glad the registrar has taken appropriate steps to rectify the error. Whether any of the affected voters choose to pursue the issue further and question the validity of the primary will be up to them.’’