As one of the biggest and most hotly contested of the swing states, Florida is the battleground on which America's next president may be decided. Billions of dollars have been spent upgrading the voting system, replacing punch ballots with computerised machines. But critics claim these new machines pose a serious threat to the democratic process. "If you make a mistake on a paper ballot, you lose your vote," explains computer expert Dr Michael Wertheimer. "You make a mistake and have the equivalent of an electronic chad, you can lose a million votes. It can happen in the blink of an eye." Last year, he was hired to examine the new voting machines. Within 10 seconds and using just a biro, his colleague was able to pick the lock safeguarding the memory cards. He was then able to amend or delete all the stored votes. The key which unlocks the memory cards is identical for all 16,000 machines. And the machines leave no paper trail which can be inspected in the event of a dispute. Wertheimer fears these flaws could be deliberately exploited: "You don't have to be that clever to go in and genuinely change this election."