Integrating RM Y-STRs into South African sexual offence casework: a narrative, problem-oriented review

Sexual and gender-based violence remains pervasive in South Africa, where rape incidence is among the highest globally. In sexual offence casework, conventional autosomal STR typing is often limited when male DNA is overwhelmed by female DNA, semen is absent, or samples are collected late. Y-chromosome STR (Y-STR) profiling provides a male-specific alternative for detecting male DNA in complex mixtures, while rapidly mutating (RM) Y-STRs improve discrimination between closely related males. However, Y-STRs also raise challenges relating to database design, match statistics, and ethical governance because Y-chromosomes are shared along paternal lines and may implicate unsampled male relatives. This narrative, problem-oriented review examines the staged implementation of Y-STR and RM Y-STR profiling in forensic services, particularly for sexual offence casework and the National Forensic DNA Database of South Africa (NFDD-ZA). It synthesises evidence on kinship and familial searching, laboratory workflows, software and databases, statistical interpretation, and legal-ethical safeguards. We propose a practical model for cautious implementation, showing that Y-STRs offer clear value in mixed or degraded samples, provided their use is supported by local population data, validated likelihood ratio frameworks, clear reporting standards, and strong constitutional safeguards.