Confusion over election rules and the crush of Election Day business caused local officials to mistakenly disqualify numerous ballots that remain uncounted to this day, an elections expert testified Friday in the courtroom contest over Minnesota's U.S. Senate recount.

The effort to add votes from rejected absentee ballots is the centerpiece of Republican Norm Coleman's court strategy as he challenges the recount results. The state Canvassing Board counted 933 previously rejected absentee ballots when it certified results showing Democrat Al Franken with a 225-vote advantage.

But other improperly rejected absentee ballots remain uncounted because of errors and varying standards applied by local elections judges, testified Ramsey County elections chief Joe Manksy.

In some cases, elections workers wrongly rejected absentee ballots because signatures accompanying them didn't appear to match those on applications, he said.

"It's a very hard thing to do because we aren't signature experts," Mansky said.

Other times, he said, election judges rejected absentee ballots for lacking a driver's license number, even though state law does not require one to be submitted with the ballots.

And some new voters put their registration form inside the secrecy envelope containing their absentee ballot, where elections officials overlooked the card and then rejected the ballot as coming from an unregistered voter, he said.

In Ramsey County, Mansky said he believes 62 rejected absentee ballots that were not tallied by the Canvassing Board should have been counted.

During a break in the hearing Friday, Coleman seized on the testimony to bolster his bid for a broad review of all 11,000 rejected absentee ballots.

"There's no question there were a number of individuals who were validly registered ... their votes should be counted," he said.. "I can't tell you how many."

But some of the remaining rejected ballots were vetoed by the Coleman and Franken campaigns. The Minnesota Supreme Court, in ordering a review of rejected absentee ballot envelopes, required agreement by county elections officials and the two campaigns for any of them to be opened and counted. While the counties identified 1,346 mistaken rejects, they and the two campaigns agreed on only 933.