Abstract

Forensic identification plays a pivotal role in criminal investigations and mass disaster scenarios. Traditional methods, such as dental records, fingerprints, and DNA profiling using short tandem repeats (STRs), have limitations in cases involving degraded samples, partial remains, or the need for investigative leads like age estimation. This review explores the emerging potential of saliva as a noninvasive, information-rich biological fluid and DNA epigenetics as a transformative tool in forensic science. Saliva is easily collectible and contains a diverse array of biomarkers, including genomic DNA, proteins, microbes, and cell-free DNA. Concurrently, DNA methylation, a stable epigenetic mark, provides a novel layer of information beyond the genetic code. This narrative review synthesizes current literature on the application of salivary biomarkers for body fluid identification, sex determination, and recent advances in age estimation. It further delves into the principles of DNA methylation, highlighting its forensic utility for constructing epigenetic clocks to predict chronological age and for differentiating body fluids through tissue-specific methylation patterns. The integration of salivary analysis with epigenetic profiling presents a powerful, complementary approach to traditional forensics. Key findings indicate that while these methodologies show immense promise, challenges regarding standardization, validation, and the influence of confounding factors remain. Future research should focus on developing robust, portable assays and expanding reference databases to facilitate the routine adoption of these tools in forensic practice.

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• 28.   Vidaki A, Ballard D, Aliferi A, Miller TH, Barron L, Syndercombe Court D. DNA methylation-based forensic age prediction using artificial neural networks and next generation sequencing. Forensic Science International Genetics. 2017 May 1;28:225–36.
• 29.   Thompson TM, Shariff F, Donnell O, Kidd D, Go JR, Kidd RC. Methylation QTLs in the developing brain and their enrichment in schizophrenia risk loci. Nat Neurosci. 2013;16(10):1348–54.
• 30.   Park J-L, Kim JH, Seo E, Bae DH, Kim S-Y, Lee H-C, et al. Identification and evaluation of age-correlated DNA methylation markers for forensic use. Forensic Sci Int Genet. 2016 July;23:64–70.
• 31.   Hong SR, Jung S-E, Lee EH, Shin K-J, Yang WI, Lee HY. DNA methylation-based age prediction from saliva: High age predictability by combination of 7 CpG markers. Forensic Sci Int Genet. 2017 July;29:118–25. .
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• 33.   Tost J. DNA methylation: an introduction to the biology and the disease-associated changes of a promising biomarker. Mol Biotechnol. 2010 Jan;44(1):71–81.
• 34.   Naue J, Hoefsloot HCJ, Mook ORF, RijlaarsdamHoekstra L, van der Zwalm MCH, Henneman P, et al. Chronological age prediction based on DNA methylation: Massive parallel sequencing and random forest regression. Forensic Sci Int Genet. 2017 Nov;31:19–28.
• 35.   Bruijns BB, Tiggelaar RM, Gardeniers H. The extraction and recovery of DNA from soil and sediment samples for forensic applications. J Forensic Sci. 2018;63(2):341–51.
• 36.   Tutton R. Sociological Perspectives on the Emergent Field of Forensic Epigenetics. Routledge Handbook of Social Studies of Forensic Science. 2018;245–58.
• 37.   Abboud A. Daubert v. In: Embryo Project Encyclopedia. Merrell Dow Pharmaceuticals, Inc; 1993.
• 38.   Samuel G, Kennett D. The ethical and legal landscape of forensic epigenetics. Forensic Epigenetics. 2020;255–70.
• 39.   Hansen HB, Damgaard PB, Margaryan A, Stenderup J, Lynnerup N, Willerslev E, et al. Comparing ancient DNA preservation in petrous bone and tooth cementum. PLoS One. 2017 Jan 27;12(1):e0170940.
• 40.   Freire-Aradas A, Phillips C, Mosquera-Miguel A, Girón-Santamaría L, Gómez-Tato A, Casares de Cal M, et al. Development of a methylation marker set for forensic age estimation using analysis of public methylation data and the Agena Bioscience EpiTYPER system. Forensic Sci Int Genet. 2016 Sept;24:65–74.
• 41.   Freire-Aradas A, Pośpiech E, Aliferi A, GirónSantamaría L, Mosquera-Miguel A, Pisarek A, et al. A comparison of forensic age prediction models using data from four DNA methylation technologies. Front Genet [Internet]. 2020 Aug 19;11. Available from: https:// www.frontiersin.org/article/10.3389/ fgene.2020.00932/full.