In 2018, the Inter-American Court delivered the first – and so far, only – judgment against Brazil on Indigenous land rights. This leading decision upheld the state's failure to comply with human rights obligations due to the non-removal of non-Indigenous individuals from the territory of the Xukuru people. Such an issue, namely, insecure land tenure affects Indigenous peoples worldwide. The decision's outcome consolidated a critical trend in international law concerning the concept of Indigenous lands: a place where Indigenous peoples have their residence and holistically develop their life, which states must actively protect, according to Article 21 of the American Convention read in conjunction with Article 1.1 and 2 thereof. By analyzing secondary sources (inter alia, ethnographies and court documents), this paper addresses the role of social (or cultural) anthropology regarding expert evidence in the Xukuru land claims. It articulates the Brazilian and Inter-American legal framework on expert evidence and Indigenous land rights with the literature on 'anthropological expertise' and 'cultural expertise', which includes the branches of forensic social anthropology and expert social anthropology. This analysis underscores the evolving challenges concerning expert evidence in legal-administrative procedures on the national and international levels. It argues that cultural anthropologists acting as experts on these levels need different sets of skills, which should be developed through special training. Thus, this paper amplifies the interdisciplinary dialogue between law and social anthropology on the topical issue of human rights adjudication. [ABSTRACT FROM AUTHOR]