Estimating Time Since Deposition of Saliva Stains Using Selected Microbial Markers: A Pilot Study
International Journal of Medical Toxicology and Forensic Medicine,
Vol. 16 (2026),
1 January 2026
,
Page 1-7
https://doi.org/10.22037/ijmtfm.v16.53149
Abstract
Background: Forensic estimation of time since deposition (TsD) of biological evidence remains challenging in forensic investigations. Saliva is commonly found at crime scenes, and determining the age of old saliva stains using traditional methods is difficult. Recent advances in microbiome analysis suggest temporal changes in saliva-associated bacterial communities and may provide a promising tool to improve accuracy in forensic investigations. The aim of this work was to predict the time since deposition of saliva stains over a 21-day period using microbial markers.
Methods: Saliva stains were collected from ten healthy volunteers. Samples were spotted onto sterilized glass slides and kept at room temperature for molecular analysis at 0, 7, 15, and 21 days after deposition. Genomic DNA was extracted from saliva stains to detect microbial markers of selected microbes (Enhydrobacter, Paenisporosarcina, and Firmicutes).
Results: Linear mixed-model analysis showed that aging time significantly affected the relative abundance of Enhydrobacter , and Paenisporosarcina . In contrast, aging time had no statistically significant effect on Firmicutes, . Multiple linear regression demonstrated that Enhydrobacter and Firmicutes significantly predicted time since deposition, , explaining 85.9% of the variance ( ). The predictive equation was: .
Conclusion: Salivary bacterial markers undergo significant time-dependent succession over 21 days under ambient conditions. Enhydrobacter and Paenisporosarcina demonstrated marked decay post-deposition, whereas Firmicutes remained relatively stable. Combining candidate bacterial markers within a predictive linear framework yielded strong explanatory power ( ), establishing microbial profiling of saliva stains as a viable quantitative approach for estimating time since deposition in forensic investigations.
- Time since deposition, Saliva Stain, Microbial Markers, Enhydrobacter, Paenisporosarcina, Firmicutes
How to Cite
References
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