The authors analyse grassroots modalities of the figure of witness in the communities living in the vicinity of uncommemorated sites of past violence. Testimoniality, understood as the disposition to bear witness, i.e. both the willingness to testify and the ability to provide important information, is discussed in relation to complex, heterogenic and dynamic assemblages that form around the sites in question, comprising both human (neighbours, wardens) and non-human actors (the landscape and biotope, material objects), diverse practices, performative gestures, and relations. The analysis is placed in the context of the debate on the complicated status of the “witness” as a category in the Polish post-war culture of memory, as well as of new relevant categories emerging in both Polish and international scholarship on the Holocaust. The authors conceptually systematise testimonial situations and propose a lexicon of testimonial positions, practices and objects that are grounded in the material gathered in fieldwork during the research project on unmemorialised sites of genocide in Poland. They distinguish: the crown witness, the trustee, the volunteer, the official and the contingent witness, and discuss categories of testimonial gesture, testimonial performance, testimonial object, and testimonial words.