After graduating law school, she was admitted to the State Bar of Wisconsin in 1989. Before serving in the judiciary, Ziegler worked as a federal prosecutor, an Assistant U.S. Attorney for the Eastern District of Wisconsin. She was also a pro bono Special Assistant District Attorney in the Milwaukee County District Attorney's Office. In private practice, she was a civil private practice attorney for several years at the law firm of O'Neil, Cannon, Hollman & DeJong, SC.
In 1997, Ziegler was appointed by Governor Tommy Thompson to the Washington CountyCircuit Court, in the Branch 2 vacancy created by the death of Judge James B. Schwalbach. She was elected to a full term in that seat in April 1998 and was re-elected in 2004, both times without opposition. She then chose to run for election to the Supreme Court seat being vacated by retiring Justice Jon P. Wilcox.
Wisconsin Supreme Court
Ziegler faced Madison attorney Linda Clifford in the April 2007 general election, after they were the top two finishers in the February primary. The campaign was contentious. Ziegler asserted that Clifford's lack of judicial experience made her ill-prepared for the Supreme Court; she also raised concerns about two of Clifford's campaign workers misrepresenting themselves to law enforcement officials. Clifford asserted that Ziegler had ruled in cases where she had a clear conflict of interest. It came to light during the campaign that Ziegler had, in fact, ruled on roughly a dozen cases affecting a bank of which her husband was a paid board member, and ruled on 22 cases involving companies in which Ziegler personally owned more than $50,000 of stock. On April 3, 2007, Ziegler defeated Clifford in the election, 58% to 42%. Ziegler's campaign and allies outspent Clifford $4.1 million to $1.7 million. The influential business lobbying associations Wisconsin Manufacturers & Commerce and Wisconsin Club for Growth spent $2.6 million in support of Ziegler. Following her election, the Wisconsin Supreme Court, in a 5 to 1 decision, took the unprecedented step of publicly reprimanding Justice Ziegler for willful violations of the code of judicial conduct, stemming from her presiding over those cases where she had an apparent conflict of interest. Ziegler's contentious election campaign and subsequent reprimand began an era of acrimony and politicization of the Wisconsin Supreme Court. In 2015, Ziegler joined the 4 person majority which ended the John Doe investigation into possibly illegal coordination between the 2010 gubernatorial campaign of Scott Walker and business lobbying associations Wisconsin Manufacturers & Commerce and Wisconsin Club for Growth. The court ruled that such coordination, if it had occurred, would be legal. The sweeping ruling upended Wisconsin campaign finance rules, enabling close coordination between campaigns and political action committees which did not have to disclose their donors. In 2017, she joined a 5 to 2 decision to strike down a rule which would have required judges to recuse from cases where they had previously received lawful campaign contributions from one of the interested parties. Justice Ziegler was re-elected in 2017 without opposition. Her current term expires July 31, 2027.
