The owner of a now closed cheese factory is facing seven negligent homicide charges after listeria was found in his products.
The case has been brought by prosecutors in canton Schwyz.
Between 2018 and 2020 a total of 34 consumers suffered a listeria infection, seven died.
In healthy people, listeria is normally mild - but it can be fatal for those suffering from autoimmune conditions.
Experts brought in by federal authorities say they can prove the infection came from the factory in the town of Steinerberg.
Prosecutors are demanding a suspended prison sentence.
The trial continues.