Résumé
Objective To explore the value of lipidic degradation in puparium cases of C.megacephala during weathering in postmortem interval estimation. Methods The puparium cases of reared C.megacephala were collected, and laid outdoor. They were taken back 5 days and 10 days later, and then be stored at -20℃. The samples of control group were cleaned and cryopreserved immediately. The spectra were collected and preprocessed. The peak position and peak height were read and performed statistical analysis by SPSS 19.0 software. Results Compared to control group, the positions of Vas CH3 band showed no shift, and the Vas CH2 band showed blue shift, meanwhile, the Vs CH2 band disappeared in both experimental groups, moreover, the Vs CH3 band showed red shift only in 10d group;except of the Vs CH3 band in 5d group, the intensities of both the other two lipidic bands reduced in both experimental groups. Compared with 5day group, the Vs CH3 band showed red shift in 10d group, meanwhile, the differences of all the lipidic bands had statistical signiifcance. Conclusion Detection of lipidic degradation in puparium cases of C. megacephala during weathering by micro-FTIR provides a novel way to estimate postmortem interval and performs its potential for forensic applications.
Résumé
OBJECTIVE@#To explore the postmortem changes of biomechanical properties of underwater corpses and value for estimating postmortem interval.@*METHODS@#SD rats were sacrificed by cervical vertebra dislocation and stored in the water at constant temperature. The vessel wall, skin, muscle, small intestine and colon were sampled at different postmortem time points (0h, 6h, 12h, 18h, 24h, 30h, 36h, 42h, 48h, 60h, 72h, 96h, 120h, 144h, 168h, 192h). The biomechanics properties of different soft tissues including ultimate load, strain, maximum stress were measured by electronic universal material testing machine.@*RESULTS@#Except for the vessel wall, the biomechanics properties of skin, muscle, small intestine and colon showed linear decrease gradually after death. Each tissue displayed its obvious "window period" for PMI estimation.@*CONCLUSION@#The time-sequential changes of biomechanical property parameters of soft tissue in underwater corpses are significantly correlated with PMI and it could be a simple and quantitive new technology for estimating PMI. The specific heat capacity of the heat-eliminating medium around the corpses probably is one of the physical factors to influence algor mortis, autolysis, putrefaction and biomechanics properties.