Gary Pierce and his wife, Sherry, have pleaded not guilty to bribery and fraud charges.

PHOENIX — Seeking to undermine her credibility, defense attorneys in the Corporation Commission bribery case got the government’s key witness to admit on the stand Tuesday she may have committed tax fraud.

Kelly Norton acknowledged that she never reported to the Internal Revenue Service the $6,000 a month she was paid over nine months in 2011 and 2012 by utility company owner George Johnson for political consulting work. That included Johnson’s desire to set up an organization for Johnson that could spend money to elect candidates to the Arizona Corporation Commission in 2012 without having to publicly disclose the donors.

That work, she said, also involved finding candidates for the Pinal County Board of Supervisors that year whose views in opposition to incorporating San Tan Valley and against the proposed Curis copper mine lined up with those of Johnson.

But while Norton never declared the $6,000 a month she got from Johnson, she did report to the IRS the $3,500 a month that she, in turn, paid to Sherry Pierce. And Norton, by reporting that expense from her personal consulting firm, in turn reduced her own taxable income.

Norton, however, said since she was made aware of the issue she has been in contact with an accountant. “Once this is all over she (the accountant) is going to put it all together and fill an amended return,” she said.

During nearly a full day of cross examination, defense attorneys also got Norton to concede that she did not produce certain emails to the FBI demanded in a grand jury subpoena. Norton said she did the best she could.

Norton admitted she posted a series of comments on Facebook about “karma,” some around the time that bribery and fraud indictments were handed up against her former husband, Jim Norton, a lobbyist for Johnson; as well as against Johnson, former utility regulator Gary Pierce and Pierce’s wife, Sherry.