Human decomposition and the reliability of a 'Universal' model for post mortem interval estimations

Area of Science:

• Forensic Science
• Thanatology
• Biological Anthropology

Background:

• Accurate post-mortem interval (PMI) estimation is crucial in medico-legal investigations.
• Existing methods based on body condition are unreliable.
• Recent universal formulas proposed for PMI estimation based on temperature and humidity.

Purpose of the Study:

• To validate two proposed universal formulas for estimating PMI.
• To assess the accuracy of these formulas for surface and buried bodies in a Canadian context.

Main Methods:

• Validation of 'Formula I' using 42 Canadian cases with known PMIs for surface decomposition.
• Examination of 'Formula II' using 22 Canadian burial cases.
• Comparison of decomposition rates across different stages for 118 cases (surface vs. buried).

Main Results:

• Formula I significantly overestimated PMI in warm temperatures and underestimated in cold (<4°C).
• Data limitations affected the validation of Formula II for buried bodies.
• Decomposition rates were inconsistent across stages, with buried bodies showing prolonged putrefaction.

Conclusions:

• The proposed universal formulas for PMI estimation demonstrated poor performance in the Canadian context.
• Regional variations in temperature and humidity likely impact decomposition rates, limiting formula universality.
• Additional, regionally specific variables likely influence human decomposition beyond temperature and humidity.