Key witness against former US Senator Edwards to return to stand GREENSBORO, North Carolina (Reuters) - A campaign aide to former U.S. Senator John Edwards was to return to the witness stand on Wednesday in the criminal trial of his ex-boss, a day after detailing ways he tried to hide the 2008 presidential hopeful's mistress from the media. Prosecutors are expected to complete their questioning of Andrew Young, after which Edwards' attorneys will have a chance to cross-examine the federal government's key witness, likely attacking his character and credibility. Already, Young has admitted there are falsehoods in his 2010 book, "The Politician," about Edwards and efforts to cover up an affair with Rielle Hunter. On Young told jurors that he agreed to falsely claim paternity of the woman's child at Edwards' request. Young and his family then accompanied Hunter to luxury locations in Florida, Colorado and California, riding in private jets and staying at fancy hotels paid for by a campaign donor, Young said. Prosecutors say Edwards, 58, manipulated Young into soliciting more than $900,000 from two wealthy donors to conceal the affair and pregnancy and avoid dooming his campaign for the 2008 Democratic presidential nomination. Edwards, then a married father of three, repeatedly denied that he was cheating on his cancer-stricken wife, Elizabeth. The government says the extramarital affair lasted from February 2006 to August 2008. Edwards faces possible prison time if convicted of federal election law violations, including charges of conspiracy, accepting illegal campaign contributions and making false statements. Among other details revealed on Tuesday, Young told jurors he often coordinated three-way phone calls between himself, Edwards and Hunter to keep the affair concealed from Elizabeth Edwards, who died in 2010. Hunter also met up with John Edwards at hotels on the campaign trail, Young said. Hunter for a time worked as a videographer for Edwards' campaign, but she lost her job after Edwards' wife found out about the affair. Young said he and Edwards discussed where they could get money to support Hunter and eventually settled on heiress Rachel "Bunny" Mellon, an Edwards admirer who is now 101. Mellon had offered to help Edwards, a two-time presidential hopeful who was the Democrats' vice presidential nominee in 2004, with campaign expenses after he took a beating in the media for his expensive haircuts. Young said he did not tell her the money would be used to cover expenses for Edwards' mistress, who had threatened to go public about her relationship with the candidate. Mellon eventually wrote seven checks totaling $725,000. Edwards says he did not know about the money from Mellon, but Young said the two men discussed the payments. Young also said Edwards directed him to enlist financial help from campaign finance chairman Fred Baron in December 2007 after a visibly pregnant Hunter said she had been surrounded by reporters as she left a North Carolina grocery store. Edwards' defense is expected to go after Young's credibility, having said during opening statements that the one-time aide pocketed most of the donor money and used it to help bankroll a $1.5 million home for his family. Editing by Dan Burns