It's been a year since Barack Obama won the presidency, but one controversy from the 2008 election in Ohio still hasn't been fully resolved: allegations of illegal voting.

Franklin County Prosecutor Ron O'Brien continues to pursue a handful of cases after prosecuting six people in voting-related cases last year, including five who cast ballots in the state even though they were not Ohio residents.

Despite loud claims of "voter fraud" in Ohio's 2008 general election, that's a minuscule percentage out of nearly 565,000 votes cast in Franklin County. And there apparently were only a handful of other such cases prosecuted statewide.

O'Brien said he wanted to file charges against other voters but couldn't for lack of evidence and because Ohio's residency laws are hazy. He urged state lawmakers to clarify residency rules for voting or risk a repeat of the 2008 controversy in the 2012 presidential election -- especially if the Buckeye State vote is close.

"We need to come up with something that's more black and white," O'Brien said.

Critics say Franklin County handled cases differently than other counties and point out that, so far, only those working on behalf of Obama have been charged -- even though supporters of Republican John McCain were in similar situations. O'Brien insists that no one got preferential treatment.

O'Brien told both presidential campaigns and volunteer groups before the election that if their out-of-state workers had no plans to remain in Ohio after the election, they should not vote in the state. The main concern was nonresidents coming to Ohio to influence the vote in a key battleground state.

Obama's main spokesman, Isaac Baker, and many Obama staff members voluntarily withdrew their Ohio registrations and absentee ballots in the historic election. But many campaign workers for McCain, including Ohio spokesman Paul Lindsay, voted in Ohio anyway and haven't been prosecuted.

Brian Rothenberg, director of ProgressOhio, a statewide liberal advocacy group, suggested that volunteers for Obama received more scrutiny than "people connected with the political establishment."

"Clearly, not everyone was treated the same way," he said.

O'Brien, a Republican, said all decisions were based on available evidence, and what prosecutors believed they could prove in court.

He said some people were investigated and cleared, including the Rev. Aaron Wheeler, who was profiled on CNN for driving 600 miles from Virginia to Columbus to vote for Obama.

Columbus attorney James B. Hadden, who represented Lindsay and four others involved with the McCain campaign, said he produced for O'Brien a Columbus lease from Lindsay and evidence that he tried to find another job in Ohio that qualified him as a state resident for voting purposes.

O'Brien also concluded that others had violated the law but that there wasn't sufficient evidence to prove that they hadn't intended to remain in Ohio as required.

"There were some guilty people that didn't get prosecuted merely because we didn't have the ability to collect the evidence in order to prosecute them," O'Brien said. "That doesn't mean that they voted properly; it doesn't mean that their conduct is sanctioned by the law or by us."

Questions began surfacing last fall about out-of-state campaign staffers and voting-rights activists coming to Ohio by the hundreds and registering to vote here.

Besides warning out-of-state campaigners not to vote here, O'Brien announced before the election that he would not press charges before the election against 13 members of the group Vote From Home as long as they agreed to cancel their registrations and have any absentee ballots already cast discarded.

The members sought to register voters while living in a small home on Brownlee Avenue on the East Side, and O'Brien suggested that others in the same position should "examine their conscience" about whether to vote.

After the election, O'Brien said his office investigated 55 people referred by the Franklin County Board of Elections based on media reports or other sources.

The cases involved allegations of voting more than once, not being U.S. citizens and improperly registering and voting -- especially during the so-called golden-week overlap between the start of early-absentee voting and the voter-registration deadline 30 days before the election.

O'Brien reached plea agreements with six people: one for voting twice and five for casting an absentee ballot when they were not Ohio residents. He said two other guilty pleas are being arranged.

O'Brien said Ohio should perhaps develop a residency checklist with items such as where a person's family lives and where he or she has bank accounts.

But the legislature is not tackling the residency issue in pending legislation to update state election administration. State Rep. Dan Stewart, D-Columbus and chairman of the House Elections and Ethics Committee, suggested that a subcommittee could be formed to study the issue.

Complicating the situation is a recent unanimous Ohio Supreme Court ruling that state Sen. Jon Husted is a legal resident of Kettering near Dayton for voting purposes, even though Husted stays with his family in Franklin County and his Kettering home shows virtually no utility use.

Although there are issues unique to state legislators in that case, the court ruled that "great weight must be accorded to the person's claimed voting residence."

Proving someone's intent is never easy, and it's also difficult to draw clear lines for how long someone must live in Ohio before or after an election to be considered a resident, said Terri Enns, a professor of election law at Ohio State University's Moritz College of Law.

mniquette@dispatch.com