Relationship between Postmortem Interval and FTIR Spectroscopy Changes of the Rat Skin.

Area of Science:

• Forensic Science
• Biophysics
• Analytical Chemistry

Background:

• Accurate postmortem interval (PMI) estimation is crucial in forensic investigations.
• Traditional methods for PMI determination have limitations.
• Spectroscopic analysis offers potential for objective PMI assessment.

Purpose of the Study:

• To develop a method for inferring postmortem interval (PMI) in rats.
• To utilize Fourier transform infrared (FTIR) spectroscopy for detecting spectral changes in dorsal skin.
• To establish a machine learning model for PMI estimation within 15 days postmortem.

Main Methods:

• Rats were maintained at controlled conditions (25°C, 50% RH) after sacrifice.
• FTIR spectral data were collected from dorsal skin at various postmortem intervals.
• Partial least squares (PLS) regression was employed for model construction.

Main Results:

• Peak intensities of FTIR spectra changed significantly with PMI, while peak locations remained consistent.
• The PLS regression model achieved a high accuracy with R² = 0.92 and RMSE = 1.30 days.
• Specific spectral bands (1760-1700, 1660-1640, 1580-1540, 1460-1420 cm⁻¹) were identified as key predictors.

Conclusions:

• FTIR spectroscopy effectively detects postmortem spectral alterations in rat skin.
• This technique provides a novel and promising approach for objective PMI estimation.
• Machine learning models enhance the accuracy and reliability of FTIR-based PMI determination.