that's where once again eric shawn contines our investigation. >> christian university professor says the touch screen about ten state, can be tampered with. >> the back door. >> in 2008 shlgs he demonstrated how as part of an election lawsuit against new jersey officials. he notes there's been no documented case of a machine being hacked this way in a u.s. election, he says it could happen. by simply swapping the machines computer chip for his own. he was able to change the votes the machine counted. >> i figured out how to make a that just before the close of the polls it shifts votes around from one candidate to another. >> our experience here in this office, we all concur that we have not seen one document the machine being compromsed. >> the deputy superintendent of election election in new jersey insists in real life it cannot be done. pointing to safeguards ha protect machines. thisser locked in secure arrest under camera surveillance and parts would show any violation. >> i don't know how you could do that to five hundred machines and get the secrecy and the teem to do so. i d