Belgium and Norway have conducted genocide-related trials. But Schurr says many European countries are failing to investigate.

He says European courts need to overcome geographical and logistical challenges to make sure that justice is done in their country, at least until a future time when the suspects can be extradited to Rwanda for trial.

"Ideally these cases take place in the countries where the crimes have been committed, as this is where most of the evidence is located and as this is where the trial will have most of the impact on the society most affected," Schurr explained. "And if it is possible for Rwanda to guarantee a fair trial of these suspects they should be sent back to Rwanda."

Onesphore Rwabukombe was formerly mayor of a town in northeastern Rwanda. He moved to Germany more than a decade ago.

Rwanda's Prosecutor General Martin Ngoga has said he welcomes the trial.