Forensic Perspectives on Human Chimerism: Identification Challenges and Detection Strategies

Chimerism is a biological condition in which a single individual harbors two or more genetically distinct cell populations originating from different zygotes. This phenomenon may occur naturally due to errors during fertilization or early embryonic development, or it may arise artificially following medical interventions such as hematopoietic stem cell transplantation (HSCT) or in vitro fertilization (IVF). Chimerism is broadly categorized as natural or artificial, and its presence presents significant challenges in both clinical and forensic contexts. In transplant recipients, the coexistence of donor- and host-derived cells can generate misleading genetic test results and complicate post-transplant monitoring. In forensic investigations, individuals with mixed DNA profiles may be difficult to identify accurately, as standard genetic fingerprinting technologies can yield inconclusive or erroneous findings. These complications underscore the necessity of reliable detection methods capable of identifying and differentiating chimeric cell populations. This review consolidates current knowledge regarding the classification of chimerism and the available diagnostic techniques, emphasizing that improved understanding of this condition is essential for enhancing diagnostic precision, optimizing forensic identification, and minimizing the risk of misinterpretation that may adversely affect medical decisions and legal determinations.