Given the political sensitivities of the story, this case has been transferred through various offices, before ultimately being taken by Barrett.
The state Capitol Police were the ones initially investigating the matter, before turning it over to the Dane County Sheriff's office. Then, Dane County Sheriff Dave Mahoney (D), who was elected as a Democrat in a partisan election and has supported liberal Supreme Court candidates and incumbent justices (including Prosser's opponent earlier this year) transferred it through a trail of his subordinates, so that he would play no active personal role in the investigation.
When the initial investigation phase was concluded, it was then turned over to Dane County District Attorney Ismael Ozanne -- who requested his own recusal, and that a judge appoint a special prosecutor. The key point here is that the incident in the court occurred during an argument over the court's decision to uphold Gov. Scott Walker's anti-public employee union legislation, with Prosser in the court's 4-3 conservative majority and Bradley in the liberal minority. And for his part, Ozanne is not only a Democratic official, but more importantly he was the lead plaintiff seeking to have the law blocked on procedural grounds.
The case was then turned over to Barrett, in neighboring Sauk County, who agreed to take the case on Judge Foust's request.
In all instances, the officials who recused themselves said that they could have conducted the investigation in a neutral manner, but that they wished to avoid even the appearance of a political conflict of interest.