The establishment of postmortem interval is one of the most important aspects of forensic expertise. Microbes may provide a novel way to estimate the postmortem intervals in order to avoid many of these limitations. The oral cavity harbors one of the most diverse microbiomes that play a key role in the decomposition of corpses. In this study, the oral bacterial community showed obvious changes in relative abundance during the process of mice decomposition. Meanwhile, at different taxonomic levels, specific bacteria were found to be significantly correlated with the postmortem interval. Linear regression models between relative abundance and the postmortem interval were constructed. Among these species, Gamma-proteobacteria andProteuswere the best ones that can be used to infer the postmortem interval, especially late postmortem interval. Therefore, we suggest that succession of oral microbial community can be developed as a forensic tool for estimating the postmortem interval.

The identification of body fluids is important in forensic science. This paper describes the application of mid-infrared and Raman spectroscopies in the non-destructive identification of human blood and semen, where other detailed information can also be obtained in one single measurement. Samples of human blood and semen were probed and characterized utilizing Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and confocal Raman spectroscopies. The result shows their ability to identify an unknown substance to be human blood or semen without the use of chemical reagents. Age determination of dried blood and semen spots through their mid-infrared spectra was investigated, which could probably be used during forensic casework. Furthermore, the origin of the Raman scattering peaks of human semen at 2907 and 2968 cm⁻¹ is detailedly analyzed, which has not been studied in previous literature. Overall, this optical detection and identification method exhibits advantages over conventional chemical methods in terms of non-destruction, high sensitivity, rapid detection and direct confirmation.