Abstract: Objective To observe the postmortem degradation process in rat myocardium and skeletal muscle using Fourier transform infrared（FTIR） spectroscopy and to provide a new method for estimating postmortem interval（PMI）. Methods Left ventricle and skeletal muscles of rats dying of mechanical asphyxiated were sampled at different PMIs. The changes of different chemical functional group in the myocardium and skeletal muscle samples were measured by FTIR spectroscopy. The different absorbance（A） ratios of peaks were calculated and the curve estimation analysis between absorbance ratios（x） and PMI（y） were performed to establish six mathematical models. Results FTIR spectral absorption peak of rat myocardium and skeletal muscle showed three changes: increase, decrease and stable. The cubic model function showed the strongest correlation coefficient. The A_{1 080}/A_{1 396} ratio of skeletal muscle showed the strongest correlation coefficient （r=0.832） with more accurate determination of PMI. Conclusion FTIR spectroscopy can be potentially used as an effective method for estimating PMI in forensic practice using myocardium and skeletal muscle.

Key words: forensic pathology, spectroscopy, Fourier transform infrared, myocardium, muscle, skeletal, postmortem interval, rats