Each of the eight relationship tests gave some ambiguity in the STR results that was successfully resolved by including SNP analysis. The SNP profiles were generated from a straightforward multiplex assay optimized and validated for forensic identification, where a very low frequency of incompatibilities in normal trios has already been established. These cases show that the addition of 52 SNPs removes the doubt involved in the interpretation of complex relationship tests that use only extended STR typing. The testing found that the combination of adding a large battery of SNPs and using "Familias" to obtain reliable probabilities for each possible relationship created a more secure framework for interpreting results. Applications likely to benefit from SNP analysis include the identification of disaster victims, immigration testing, complex pedigree reconstruction, and the analysis of deficient families. The latter is often the case in attempting to identify missing persons. The paper's descriptions of materials and methods used address the marker sets, statistical analysis, the simulation of testing a first-degree relative of the true father, and the relationship tests examined. 3 tables, 2 figures, and 16 references