Estimation of postmortem interval using attenuated total reflectance: Fourier transform infrared spectroscopy in adipose tissues

Estimation of postmortem interval (PMI) is vitally important in forensic investigations. Although many studies have examined the chemical changes of various tissues over time, no reports using spectroscopic methods in adipose tissue are available. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was utilized to collect comprehensive biochemical information from human adipose tissues in vitro at different times. Thereafter, mice were used as samples for in vivo experiments for more detailed studies on PMI. Then, partial least squares (PLS) model for PMI estimation was established based on the acquired spectral dataset of mouse samples. The spectral variable associated with C=O arising from lipids and free fatty acids was most susceptible to PMI. Moreover, the PLS model appeared to achieve a satisfactory prediction with a root mean square error of cross-validation of 1.78 days, and the reliability of the model was determined in an external validation set with a root mean square error of prediction of 1.87 days. The study shows the possibility of application of ATR-FTIR methods in PMI estimation using adipose tissue.