Cook County State’s Attorney Kim Foxx on Friday announced that one of her top deputies had resigned after a review showed his former law firm had billed the county more than the county standard rate.

Chaka Patterson, a Harvard-educated lawyer and prodigious fundraiser for former President Barack Obama, leaves the State’s Attorney’s office less than a year after he left his job as a partner at the Chicago office of the multinational law firm Jones Day.

In June, county records show Patterson hired Jones Day to handle two cases, with the firm eventually billing the county for some $460,000.

A statement from Foxx spokesman Robert Foley said the firm had done “nothing inappropriate,” but noted that Jones Day had billed the county “significantly in excess of the standard county rate” for legal services.

“The State’s Attorney’s Office has no reason to believe that Mr. Patterson’s former firm has done anything inappropriate and recognizes that his former firm has done substantial work for the State’s Attorney’s Office on a pro bono basis,” Foley’s statement reads.

The county rate is $185 an hour. County records indicate the firm billed at rates ranging from $95 to $500 an hour.

Among more than 60 outside firms hired to represent the county, only Jones Day and five other firms were listed as having a top rate higher than $185, and only one firm had a top rate higher than the $500 per hour paid out for the work of top lawyers from Jones Day.

Patterson had been praised by Foxx for his experience in both the public and private sector. Patterson did not have an “ongoing financial relationship” with the firm after joining Foxx’s staff, Foley said.

A Jones Day spokesman did not immediately return calls from Chicago Sun-Times.

Another outside firm, working pro bono, will review the State’s Attorney’s practices for hiring lawyers, and their report will be made public.

Meanwhile, the State’s Attorney will farm out appointments of outside lawyers to a judge, who will approve the firm and their billing rate.