Application of X-STRs for Forensic Identification in Mixed DNA Profile: A Case Report

Autosomal polymorphisms (STRs) or Y-Chromosome polymorphisms (Y-STRs) are usually used for the study and deconvolution of mixed DNA profiles in forensic genetics, accompanying data interpretation with biostatistical evaluations (e.g., RMP, RMNE, LR). Sometimes, however, some mixed DNA profiles are so complex that autosomal and Y markers are not sufficient for correct discrimination and identification. In this work is reported a robbery case in which the analysis of the polymorphic markers of the X Chromosome (X-STRs) was applied to the mixed profiles obtained from the traces. This falls outside the classic use of the X-STRs. Indeed, the aim of the authors is to encourage the usage of X-STRs not only in parental relationships, but also in pure forensic cases for interpreting complex mixed DNA profiles, since their application in case resolution could be more decisive than autosomal STRs and Y-STRs.