Study on estimation of postmortem interval using FTIR in rat lung

Fourier transform infrared spectroscopy (FTIR) was applied to study the decomposition process postmortem in rat lung tissue and provided a new method for the estimation of postmortem interval (PMI). The results demonstrated that, with the PMI increasing, the peak position of main absorbance bands showed no significant difference, but there was obvious variance of intensity: (1) The intensity of 1080 and 1241 cm^-1 related to nucleic acid tended to decrease. (2) The intensity ratio at Amide I (I₁₆₄₇) and II (I₁₅₄₁) decreased since death. The intensity of 1338 and 1313 cm^-1 increased lightly. (3) The intensity at 1460, 1400 and 1170 cm^-1 showed no significant difference. (4) A new band at 1120 cm^-1 appeared since 72 h after death and its intensity increased from 72 to 144 h postmortem. The authors' preliminary results suggest that it may be possible for FTIR to become an effective method to estimate the PMI in forensic practice.