In 2004, when touch-screen voting machines were widely deployed for the first time in a national election, concerns about the security and reliability of the machines--and therefore, the integrity of election results--abounded. Since then, some election officials have adopted voter-verified paper audit trails (VVPATs) to improve the reliability of election results. Security holes continue to be discovered, however; and of the 32 states that use touch-screen machines, only 17 require that the machines produce paper trails.
Moreover, the paper trails themselves pose new and unexpected problems, says David Dill, a Stanford University computer science professor and the founder of VerifiedVoting.org, one of the leading proponents of mandatory paper trails for e-voting machines. Paper-trail systems may fail for mechanical reasons or through human error, as they did in Ohio this year.