Discrepancies between expected and recovered individuals in exhumed mass graves at Paterna Cemetery (Spain): aggregate analysis of 15 official exhumation reports

Background: Pre-exhumation estimates of the number of individuals expected to be present in a grave are routinely used to guide fieldwork planning, laboratory workflows, and communication with families. However, the degree to which these expectations match the number of individuals actually recovered can vary across contexts and burial features. Aim: To quantify the discrepancy between the number of individuals expected prior to exhumation and the number recovered after exhumation in a set of exhumed mass graves at Paterna Cemetery, using an aggregate (global) recovery proportion derived from official reporting. Materials and methods: For each mass grave, two counts were extracted from official reporting: a) the number of subjects to be found before exhumations (NSTBF; expected); and b) the real number of subjects found after the exhumations (RNSF; recovered). Recovery percentage per mass grave was defined as RNSF/NSTBF. The primary outcome was the global recovery proportion computed as ΣRNSF/ΣNSTBF across all included mass graves. Results: Across 15 mass graves, 1180 individuals were expected and 1048 were recovered, yielding a global recovery proportion of 0.888 (88.8 %). The overall shortfall relative to expectations was 132 individuals (11.2 %). Mass graves recovery ranged from 0 % (0/20) to 100 % (e.g., 42/42; 98/98; 107/107). Eight of fifteen mass graves showed ≥ 90 % recovery, whereas two showed < 10 % recovery (1/19 and 0/20). Conclusions: In this set of exhumed mass graves, recovery totals were lower than expected overall when aggregated across features. The magnitude and variability of the shortfall support incorporating uncertainty into operational planning for recovery and identification rather than assuming expected counts will be fully recovered.