Post-mortem interval estimation of skeletal remains using spectroscopic analysis: a systematic review

Recent advances in spectroscopy for post-mortem interval (PMI) estimation have shown spectroscopy to be a promising, timely and cost-effective tool. However, its degree of applicability has not been adequately addressed.

This systematic review aimed to synthesise studies on PMI estimation methods of skeletal remains using spectroscopic analysis published between 2015 and 2025.

A systematic database search was conducted adhering to PRISMA-2020 guidelines. The selected studies analysed changes in skeletal remains (bones and teeth) using spectroscopic methods to estimate PMI. Data extraction and risk-of-bias assessment (JBI) were performed independently by two reviewers. Results were synthesised narratively as heterogeneity prohibited meta-analyses.

A total of 19 studies were selected. The most used spectroscopic modalities were Fourier-transform Infrared Spectroscopy (FTIR) (n = 10) and Raman spectroscopy (n = 7), with FTIR generating the more consistent data. Common parameters studied included phosphate, carbonate, amide, and calcium levels, with variations in ratios. Differences were seen between archaeological and forensic remains. However, the differences were not always significant (p > 0.05), especially in skeletal remains with PMI timescales less than 90 days. Machine-learning models integrating obtained spectrums achieved 58-100% accuracy. Risk-of-bias was low, with all selected studies scoring 6.0 and above.

Whilst spectroscopy shows great potential as a PMI estimation tool, with selected parameters showing consistent trends across time, its degree of applicability remains questionable for differentiating skeletal remains of short PMI (less than 90 days). Future studies warrant considerations of protocol standardisation, external validation, multimodal integration, and the incorporation of machine-learning approaches to develop robust PMI estimation tools.