By Brendan O'Brien
MILWAUKEE (Reuters) - A Wisconsin district attorney on Friday formally closed a three-year probe of Governor Scott Walker's staff when he was Milwaukee County executive, lifting a major political cloud hanging over the controversial Republican.
Milwaukee County District Attorney John Chisholm said that after he determined no new charges would be filed he asked the judge overseeing the secret investigation to close the case.
Judge Neal Nettesheim, a retired appellate court judge, granted the request and closed the investigation on February 21.
"I am glad the process has been completed," Walker said in a statement, noting that he originally requested the district attorney to open an investigation.
"We appreciate the effort that was undertaken and to bring appropriate matters to justice," he added.
The closing of the investigation culminates a tumultuous three years for the first-term governor.
In addition to the looming investigation, Walker was forced into a special election after he angered Democrats and union members by spearheading the passage of collective bargaining reforms that sharply limit the power of public sector labor unions.
Walker, who is up for re-election in 2014, became the first governor in U.S. history to survive a recall in June, 2012 when he defeated Milwaukee Mayor Tom Barrett in the special election.
Walker, who was Milwaukee County executive from 2002 to 2010, was not charged in the investigation.
The investigation began in May 2010. It resulted in charges filed against six individuals, including four of Walker's aides.
Kevin Kavanaugh was sentenced to two years in prison in December for embezzling $51,200 from a fund for families of U.S. soldiers who fought in Iraq and Afghanistan.
Tim Russell, another Walker aide, was implicated in the same investigation and pleaded guilty in November to diverting more than $21,000 to his personal bank account. He was sentenced to two years in prison in January.
Kelly Rindfleisch, who was Walker's deputy chief of staff, pleaded guilty to felony misconduct in public office in October and was sentenced to six months in jail after admitting to campaigning for Republicans while working in Walker's office for Milwaukee County.
Darlene Wink, a former executive assistant in the county executive's office, pleaded guilty to charges of political solicitation by public officials. She was sentenced to a year of probation in January.
(Reporting By Brendan O'Brien; Editing by Greg McCune and Andrew Hay)