The Federal Court is set to rule on a challenge to the narrow approval of the Swiss e-ID law.
The measure passed with just 50.4 percent of the vote last September.
Opponents argue the result was skewed by support from state-linked Swisscom and undisclosed media backing, and are calling for the vote to be annulled.
The case now sits before the Federal Supreme Court of Switzerland, which will hold a public hearing tomorrow.
If judges side with the complainants, the referendum could be rerun.
If that happens it will be highly unusual - the court has ordered a federal vote to be rerun only once since 1848 - in 2019 it decided the ‘for marriage and family’ initiative needed to be held again after the federal council had provided incorrect information to the voters.
Lausanne pedestrians have handed the city a petition with nearly 1,000 signatures, demanding action against cyclists and e-scooter riders who ignore pedestrian zones
Switzerland's Nepalese and Tibetan communities are still waiting for word from relatives after violent floods tore through a Himalayan valley last Wednesday
A 22-year-old woman has been identified as the victim of Saturday’s Aarau rave shooting, and German police have joined the Swiss manhunt for the gunmen still at large