During the Nuremberg Trials , Sigmund Mazur , a laboratory worker at the Danzig Anatomical Institute , testimony that soap had been made from the bodies of dead people at the camp , and claimed that 70 to 80 kg of fat collected from 40 bodies could produce more than 25 kg of soap , and that the finished soap was retained by Professor Rudolf Spanner . During the Nuremberg Trials , Sigmund Mazur , a laboratory assistant at the Danzig Anatomical Institute , testified that soap had been made from corpse fat at the camp , and claimed that 70 to 80 kg of fat collected from 40 bodies could produce more than 25 kg of soap , and that the finished soap was retained by Professor Rudolf Spanner .