ABSTRACT
Postmortem interval (PMI) estimation is one of the most challenging problems in the field of forensic science. Vitreous humor is a hotspot which has been used for PMI estimation and postmortem chemical analysis in forensic pathology. In order to provide novel perspectives for the future research of PMI estimation using vitreous humor, the comparison between vitreous humor with other common body fluids, the effect of temperature on vitreous humor, vitreous humor detection method and data fitting method have been reviewed in this paper.
ABSTRACT
Objective To test the changes of the potassium(K+)and magnesium(Mg2+)concentrations in vitreous humor of rabbits along with postmortem interval(PMI)under different temperatures, and explore the feasibility of PMI estimation using mixed-effect model. Methods After sacrifice, rabbit carcasses were preserved at 5℃, 15℃, 25℃ and 35℃, and 80-100μL of vitreous humor was collected by the double-eye alternating micro-sampling method at every 12 h. The concentrations of K+and Mg2+in vitreous humor were measured by a biochemical-immune analyser. The mixed-effect model was used to perform analy-sis and fitting, and established the equations for PMI estimation. The data detected from the samples that were stoned at 10℃, 20℃ and 30℃ with 20, 40 and 65 h were used to validate the equations of PMI estimation. Results The concentrations of K+and Mg2+[f(x,y)] in vitreous humor of rabbits under different temperature increased along with PMI(x). The relative equations of K+and Mg2+concentration with PMI and temperature under 5℃~35℃ were fK+(x,y)=3.413 0+0.309 2 x+0.337 6 y+0.010 83 xy-0.002 47 x2 (P<0.000 1), and fMg2+(x,y)=0.745 6+0.006 432 x+0.033 8 y(P<0.000 1), respectively. It was proved that the time of deviation for PMI estimation by K+and Mg2+was in 10 h when PMI was between 0 to 40 h, and the time of deviation was in 21 h when PMI was between 40 to 65 h. Conclusion In the ambient temperature range of 5℃-35℃, the mixed-effect model based on temperature and vitreous humor sub-stance concentrations can provide a new method for the practical application of vitreous humor chemi-cals for PMI estimation.