After a massive manhunt, in May 2016 a 33-year-old Swiss student was arrested and admitted murdering a 48-year-old mother, her two sons and the girlfriend of the older son at the family's home.
In the course of the investigation, Aargau authorities requested data from 48 mobile phone masts to track the phone numbers of some 30,000 people in the area at the time of the crime, reported the Aargauer Zeitung on Wednesday.
That information was gathered by an independent telecommunications surveillance body working under the auspices of the Swiss federal justice department.
Now Aargau faces a 800,000 franc bill for that search – and the canton isn't happy.
Speaking to the paper, a spokesman said the canton felt the 800,000 franc fee was not proportional to the actual costs incurred.
Now, after failing to come to an agreement with the surveillance body, Aargau plans to contest the bill in Switzerland's highest civil court.
Though the bill came from the federal authorities, the justice office said it gets none of the fee itself, and that most of it would go to the mobile phone network operators that provided the data.
The canton was informed before it requested the data that a fee would be incurred, said the paper, but chose to give priority to catching the murderer and clarify the costs later.
The case is expected to be heard in court this summer – and it will be the first time anything related to the Rupperswil murders goes before a court, since the trial of the accused has not yet begun.