It was simultaneously an uh-oh moment and an ah-ha moment.

When Sequoia Voting Systems demonstrated its new paper-trail electronic voting system for state Senate staffers in California last week, the company representative got a surprise when the paper trail failed to record votes that testers cast on the machine.

That was bad news for the voting company, whose paper-trail, touch-screen machine will be used for the first time next month in Nevada's state primary. The company advertises that its touch-screen machines provide "nothing less than 100 percent accuracy."

It was good news, however, for computer scientists and voting activists, who have long held that touch-screen machines are unreliable and vulnerable to tampering, and therefore must provide a physical paper-based audit trail of votes.