Abstract: Objective To investigate the expression of caspase 3 and iNOS in different intervals and to provide evidence for estimation of injury intervals after brain contusion in human. Methods Thirty cases died of serious brain injury were included into the injury groups and 5 cases died of non-brain injury were served as control group. To analyze the changes of caspase 3 and iNOS expression in brain samples at different intervals(2 h, 4-8 h, 10-14 h, 1-2 d, 3-5 d, 8-11 d) by immunohistochemistry and auto-image analysis system. Results The level of caspase 3 expression started to increase in 2 hours after brain contusion compared to the control group(P<0.05). The level of caspase 3 expression continued to increase in 1-2 days and maintained high level in 3-5 days compared to the control group(P<0.05), then decreased gradually. There was no statistically significant difference between the expression level of iNOS in 2 hours with the control group(P>0.05). But the expression level of iNOS began to increase in 4-8 hours after brain contusion and reached its maximum in 1-2 days, then decreased. Weak expression of iNOS still could be detected in 8-11 days. Conclusion The expression of caspase 3 and iNOS can be used as effective evidence for human brain contusion interval.

Key words: forensic pathology, brain injuries, caspase 3, iNOS, wound age estimation