When an inconsistency occurs in a pedigree, it may not be apparent which individual(s) are causing it. Here, a statistical method is described which identifies individuals most likely to have caused an inconsistency. The method is based on the sum of squared deviations between two predictors of an individual’s genotypes: (1) that given an individual’s own phenotype, and (2) that given all phenotypes in the pedigree. Extreme deviations between the two arrays (measured in terms of a sum of squares) are interpreted as indicating an inconsistency. The method is applied to a pedigree with an inconsistency in which it is unclear who is causing the inconsiste