Edwards is on trial for using campaign funds to cover up his affair with Rielle Hunter, who worked on his campaign team as a videographer.
Andrew Young, a former campaign staff member, said he and Edwards would talk about ways of getting money to support Hunter after Edwards' wife learned of the affair and demanded that Hunter be fired, The New York Times reported.
Young said he and Edwards discussed which campaign donors to ask for financial aid for the cover up and they settled on Rachel Mellon, a banking heiress. Checks from Mellon were sent to Young and then used to pay Hunter's living expenses.
Edwards allegedly told Young at one point Edwards was not supposed to know about the checks.
"He said he couldn't know about any of this in case he needed to be sworn in as attorney general," Young testified.
Young and his wife soon became worried that the money they were receiving from Mellon would put them in legal trouble, Politico reported.
"It was crazy," Young said. "We were all scared to death. He was a viable presidential candidate and this was a truckload of money, much more than had ever flowed through our account."
Young said he approached Edwards with his concerns, but was told not to worry.
"He was frustrated with me asking him so many times. He told me he'd talked to several campaign finance experts and it was absolutely legal," Young said.
If convicted on the six felony counts, Edwards faces a possible 30 years in prison and $1.5 million in fines.