Three accused eco-terrorists went on trial in Switzerland's highest criminal court Tuesday for their involvement in an alleged plot to blow up an IBM research center near Zurich.

The trial for Costantino Alfonso Ragusa, his wife Silvia Ragusa Guerini and their Swiss friend Luca “Billy” Cristos Bernasconi opened one hour late due to the security measures taken by Swiss police.

At least 50 protesters gathered outside the courthouse to demand freedom for the defendants. The three alleged eco-terorists have been in custody since April, 2010, when they were arrested with explosives and bomb-making materials in their car.

Police said they also found dozens of letters claiming responsibility for the planned attack, signed by “ELF Switzerland, Earth Liberation Front,” which stated the goal of stopping the destruction of the environment.

The IBM facility explores using nanotechnology to manipulate and make new materials between one and 100 nanometers in size; one nanometer equals one billionth of a meter.