(1) Background: Insertion-deletion (InDel) markers show the advantages of both short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) and are considered alternative markers in forensic genetics. (2) Methods: Allelic frequencies and corresponding forensic efficiency parameters of 30 autosomal polymorphic InDel loci included in the Investigator DIPplex kit (Qiagen) were obtained in a sample of 631 unrelated Polish individuals. Allelic frequency data were compared with those reported for selected populations (3) Results: All the loci conformed with Hardy-Weinberg equilibrium after applying a Bonferroni correction and no pair-wise significant linkage disequilibrium was detected. (4) Conclusions: DIPplex Kit differences were high among populations worldwide. The InDel markers are highly discriminating for human identification purposes in the Polish population.

Introduction: In legal paternity cases, genetic testing holds crucial evidential value. The standard practice involves the participation of the mother, child, and alleged father in these tests. There is an approach that considers the child’s mother’s profile unnecessary for such tests. While testing fewer participants may be cost-effective, it is essential to obtain clear and conclusive results. Therefore, it is worth examining whether the absence of the mother’s profile in the tests negatively impacts the results of kinship analysis.Materials and methods: The results of disputed paternity genetic tests that included the mother, child, and alleged father were evaluated. These tests were conducted between 2018–2023 at the Department of Forensic Medicine of the Medical University of Warsaw. Genetic profiles were obtained using the PowerPlex® Fusion 6C System reagent kit (Promega, USA).Results: Analysis of 557 paternity tests revealed that 148 cases resulted in the exclusion of paternity, 406 confirmed paternity, and 3 cases remained unsolved. Further analysis of cases with paternity exclusions showed inconsistencies in an average of 14 loci. The most frequently excluding marker was SE33, while TPOX had the weakest excluding strength. No false positive results were obtained in tests that included the mother’s profile, and the percentage of unresolved cases was 0.54%. When simulating the results without the mother’s profile, 5.21% of cases remained unresolved, and it was determined that a false positive result could occur.Conclusions: The necessity of the mother’s participation in genetic paternity testing has been confirmed. Omitting the mother’s profile may lead to an inconclusive result or even an erroneous genetic opinion.