As part of the prosecution's case, historian Dr. Dieter Pohl of the University of Klagenfurt testified that Sobibor was a death camp, the sole purpose of which was the killing of Jews, and that all Trawniki men had been generalists involved in guarding the prisoners as well as other duties; therefore, if Demjanjuk was a Trawniki man at Sobibor, he had necessarily been involved in sending the prisoners to their deaths and was an accessory to murder. The prosecution further argued, using Pohl's testimony, that Demjanjuk's choice after being captured by the Germans was guard duty or forced labor, not death, the Trawniki guards were a privileged group that was essential to the Holocaust, and that Demjanjuk's failure to desert, something many Trawniki guards did, showed that he had been at Sobibor voluntarily.