Assessment of consistency of minimum post-mortem intervals estimated by thermal summation-based methods in medico-legal cases associated with blowflies.

Background: This study is based on blow fly samples collected from 8 medico-legal cases in Tamil Nadu, India. The fly life stages were identified and the consistency of minimum post-mortem intervals (PMImin) estimated by different thermal summation-based methods was assessed.

Methods: PMImin of 8 medico-legal cases was estimated using six different thermal summation constants and lower developmental temperatures that are based on C. megacephala and C. rufifacies developmental data. Limits of agreement (LoA), intra class correlation coefficient (ICC) between PMImin values and margin of error of mean of difference between PMImin values were calculated.

Results: Intra-class correlation between the PMImin values estimated using different thermal summation constants based on C. megacephala ranged between 0.89 and 0.98 and coefficient of determination ranged between 0.93 and 0.98. Intra-class correlation between the PMImin values estimated using different thermal summation constants based on C. rufifacies ranged between 0.91 and 0.99 and coefficient of determination ranged between 0.95 and 0.99. The mean difference of PMImin values estimated using different thermal summation methods based on C. megacephala ranged between 1.8 hr and 6.6hr and margin of error ranged between 2.51 and 6.93hr. The mean difference of PMImin values estimated using different thermal summation methods based on C. rufifacies ranged between 3.33 and 31.33hr and margin of error ranged between 4.66 and 32hr.

Conclusion: Consistency of PMImin values estimated by different thermal summation methods was good to excellent. Thermal summation constants useful in estimation of PMImin with lowest mean difference and margin of error were described.