Early voters for the presidential election have reported that when they tried to vote for one candidate, their touch screen machine selected another. Could these "faulty" machines decide who's the next US president?

After the vote counting fiasco in Florida in 2000, US polling stations were ordered to update their systems to avoid inaccuracies under the Help America Vote Act 2002. But six years and $3 billion dollars later, new touch screen machines, used in around a quarter of polling booths, are causing even more trouble than the old hole-punchers.

This year has seen record numbers of early voters, expected to amount to a third of the total electorate, who choose to make their decision before the 4 November deadline. But in West Virginia, where the booths opened on 23 October, voters have emerged from polling stations complaining that the machine didn't respond to the choice they made, but selected another. Whether the machines are being rigged; or defective technology is at fault, Americans are terrified that after eight months of decision making, their vote will go to the wrong candidate. Campaigners for democracy are spreading the message: check your screen to make sure you've voted for the right person.

"I don't think it's foul play because it would be a pretty stupid way to go about it"

Lawrence Norden is project director for the Voting Technology Project, working in the areas of voting systems, voting rights and government accountability. He also writes for the ReformNY blog and New York University School of Law's The Brennan Center for Justice.

This is known as "vote-flipping", [and is] caused by what is referred to as a "calibration" problem. Touch screen machines are calibrated in advance so that when a voter presses on the screen, the machine can interpret it as a vote for a particular candidate. Particularly after a few hours of voting, the calibration on these machines can slip - or they may not have been properly calibrated in the first place. There is a question about how often this happens, and it certainly shouldn't happen as much as it does.

The reason a lot of polling stations bought these touch screen machines was because after 2002, there was a deadline set for new equipment by 2006. A lot of money was spent, but there wasn't enough time to adequately test the machines. It's taken a few years to understand just how to test them. Everyone said that touch screens were the future. But by 2004 reports of problems started cropping up and grassroots organisations protested against them. Since 2006, using paper ballots with a scanner starting catching on again, and many places are now getting rid of their touch screens. At the moment around 25 - 30% of Americans use this kind of machine. The majority cast their votes on paper ballots.

At least if they [touch screens] are used, they do create a print out, called a paper trail, which lists all the votes, so they can be checked afterwards. I don't think it's that bad; most people would notice at the end of voting, because it gives you a review screen. However, it is very disconcerting; it leaves voters with little confidence. But I don't think it's foul play because it would be a pretty stupid way to go about it. If you were going to try to steal someone's vote, you wouldn't then show them with the review screen."

"This machine is out of calibration"

Video the Vote went to the problematic polling station to check out how the machines function. The video, apparently featuring County Clerk Jeff Waybright, came under fire for allegedly being false after it was posted on 27 October. In response, Video the Vote posted the footage in its entirety on 29 October.

"Why will this machine not allow me to vote for my candidate?"

Virginia Methaney was interviewed by Video the Vote, a group that urges people to film themselves as they vote and send then the footage to the website, in an attempt to improve transparency. This video was filmed in one of the areas worst affected by the faulty touch screen: Jackson County, West Virginia, on 23 October 08.