Scientists told a federal panel Wednesday that electronic voting isn't completely reliable and suggested a backup paper system might be the only way to avoid another disputed presidential election in November.

But the commission's chairman said he didn't expect the bipartisan panel would issue national standards requiring paper receipts when it makes preliminary recommendations next week, followed by more detailed guidelines next month.

"We will not decide on what machines people will buy," said Republican DeForest B. Soaries Jr. (search), chairman of the newly created U.S. Election Assistance Commission (search), saying it wasn't the panel's role to tell states what to do. "We will say, if California wants to have a backup paper system, what national standards it should follow."

At least 20 states are considering legislation to require a paper record of every vote cast after rushing to get ATM-like voting machines to replace paper ballots after Florida's fiasco with hanging chads in the 2000 presidential election. About 50 million people, or 29 percent of voters, are expected to vote electronically.

In California, a state Senate panel gave preliminary approval Wednesday to a proposed ban on electronic voting machines in the Nov. 2 election, less than a week after the secretary of state decertified the machines in four counties. The bill would not allow use of any form of electronic voting, including touch-screen machines, and would apply only to that election.

Aviel D. Rubin, a computer science professor at Johns Hopkins University, summed up the testimony of several science witnesses when he criticized electronic voting systems as terrible and highly vulnerable to hackers.

"Not only have the vendors not implemented security safeguards that are possible, they have not even correctly implemented the ones that are easy," he said.

Others argued that electronic voting offers advantages over paper punch cards, such as the inability to vote twice. They warned that backing up electronic systems with paper ballots could be costly and create unnecessary confusion for voters and poll workers.

"We would be negligent in our duty if we foisted an untested and untried experiment upon the voters," said Kathy Rogers, director of election administration for Georgia, which switched to electronic voting in 2002.

If 1 percent of Georgia precincts had problems because of demands of new, complicated equipment under a backup paper system, Rogers said, that would comprise "a situation that no doubt would be portrayed by the media and perceived by the public as a catastrophic failure."

The issue has potentially huge ramifications. Vendor groups that developed electronic polling have a financial stake, while state and local officials fear a last-minute change that would require new equipment and additional training of thousands of poll workers.

Voting rights groups, meanwhile, worry about a potential recount that lacks a paper trail, and non-English speakers and the visually impaired favor an electronic system that empowers them to vote without the aid of a poll worker.

Phil Singer, a spokesman for the presidential campaign of Democrat John Kerry (search), said Wednesday, "After what happened in Florida in 2000, making sure that there is a reliable paper trail in place to account for every vote is just common sense."

Florida Gov. Jeb Bush (search) told reporters that printers for making receipts have not been manufactured for the electronic voting machines in his state, but he suggested he is not concerned about using the machines in November.

"I'm afraid a lot of the concerns about this are really to try to create a cloud of controversy during the election to motivate people to vote and there's got to be a better way to do that," Bush said. "You can talk about issues and ideas, maybe, instead of scaring people."

During the March 2 presidential primary, machines that determine which ballots voters receive malfunctioned in about one-third of the precincts in California's San Diego County, and officials there say a lack of paper ballots may have disenfranchised some voters.

Congress created the commission under the 2002 Help America Vote Act, which began distributing $3.9 billion to states to upgrade voting systems after the disputed 2000 election.

The commission has said it is woefully underfunded, with only $1.2 million of its $10 million budget appropriated. Because of the funding problems, it has not scheduled additional hearings.