Before the Inquisition, border communities in Spain had their share of violence – and some of it was committed by Jews against others Jews, even by Jewish communal leaders against Jewish community members. And many Jews' greatest fear was that reporting the crimes to the Crown would cause Jewish community leaders to label them mosrim, informers – with all the danger and negative connotations that implied.
From Jonathan Ray, The Sephardic Frontier: The "Reconquista" and the Jewish Community in Medieval Iberia, pages 133-136. Please click to enlarge (the easiest thing to do is to right click each image and open in in a new browser window or tab):
[Hat Tip: Sanhedrin.]