The country's top court is set to rule today on whether voting irregularities in the Toronto riding of Etobicoke Centre in 2011 were bad enough to overturn the result, forcing a byelection.

A lower court judge made that very decision last May, and the Supreme Court heard an appeal of the ruling over the summer.

Whatever the Supreme Court decides will likely affect the way elections are run in Canada from now on.

Voting rules could be interpreted more liberally in future, even though low turnouts have led to some nail-bitingly close elections in recent years.

Or, a much tighter ship could be in order, pushing Elections Canada to spend a lot more time and money on training polling day officials.

In April, the incumbent Liberal MP who lost the riding of Etobicoke Centre by just 26 votes brought a court challenge to contest the results. Borys Wrzesnewskyj's case was based on numerous "irregularities" in Election Day paperwork.

Justice Thomas Lederer of the Ontario Superior Court of Justice, using a sample of polls from just five percent of the riding, agreed there were enough concerns to throw out 79 ballots, overturning the result and paving the way for a byelection.

The sitting MP Conservative, Ted Opitz, appealed directly to the Supreme Court of Canada. He argued, "To allow any mistake, error or non-compliance to overturn the result of an election would lead to a never-ending series of contested election challenges in ridings where the results are even remotely close."

It should be a given, Opitz contended, that voters and elections officials are honest, unless there is evidence of fraudulent activity.

Voting irregularities

In his May 18 ruling, Justice Lederer found no evidence of wrongdoing by either Wrzesnewskyj or Opitz, and no evidence that any voters had acted illegally.

But he did find "irregularities that affected the result of the election" by applying two tests:

• Were there ballots in the box that should not have been there?
• Were there voters who voted who should not have been permitted to vote?

Most of these irregularities were about registration certificates, which are the documents voters fill out if they turn up at a polling station where they are not on the voters' list.

A registration certificate records the voter's name, address and, most importantly, signature, which is a statutory declaration that he or she is over 18 and a Canadian citizen.

For 41 voters in Etobicoke Centre, there was no evidence registration certificates had been filled out at all. Others lacked the crucial voter's signature. The judge said, "The problem that arises is whether there is any way of knowing whether these people are Canadian citizens."

The judge also rejected ballots for vouching errors or complete lack of vouching paperwork. Vouching occurs when potential voters show up with no ID at all, and someone from the same polling division who knows them vouches as to their identity.

Wrzesnewskyj's cross appeal

Wrzesnewskyj originally contested 181 ballots. Although Justice Lederer agreed that 79 should be voided, Wrzesnewskyj argues, in a cross appeal, that others should have been trashed as well.

He objects to the fact that the judge approved many ballots cast in the wrong polling division, as long as the voters lived in the riding, “in the absence of any suggestion of double voting.”

In his cross appeal, Wrzesnewskyj argues that elections officials should not be "freelancing” as to who can vote at their respective polling stations.

In its submission to the Supreme Court, Elections Canada allowed there is some leeway for voters who vote at the wrong polling station.

Opitz argues that Wrzesnewsyj is urging "a standard of perfection" and points out there is no evidence that anyone voted twice.

Elections Canada can cross-reference and determine if someone with the same name voted twice, but it admits that this check can't be done at polling stations on Election Day.

Justice Lederer wrote tellingly about the "conundrum" he faced in coming to his decision. He said Canadians need to have confidence in the fairness of the electoral system, yet if an election is set aside too easily — given that "mistakes in the record are inevitable" — then every close election would be subject to challenge.

It's this conundrum that the Supreme Court of Canada has had to face.

Read Kady O'Malley's liveblog from the Supreme Court:

Mobile-friendly liveblog also available.