ABSTRACT
Objective To analyse the relationship between Fourier transform infrared （FTIR） spectrum ofrat's spleen tissue and postmortem interval （PMI） for PMI estimation using FTIR spectroscopy combinedwith data mining method. Methods Rats were sacrificed by cervical dislocation, and the cadavers were placed at 20 ℃. The FTIR spectrum data of rats' spleen tissues were taken and measured at different time points. After pretreatment, the data was analysed by data mining method. Results The absorption peak intensity of rat's spleen tissue spectrum changed with the PMI, while the absorption peak position was unchanged. The results of principal component analysis （PCA） showed that the cumulative contribution rate of the first three principal components was 96%. There was an obvious clustering tendency for the spectrum sample at each time point. The methods of partial least squares discriminant analysis （PLS- DA） and support vector machine classification （SVMC） effectively divided the spectrum samples with different PMI into four categories （0-24 h, 48-72 h, 96-120 h and 144-168 h）. The determination coefficient （R2） of the PMI estimation model established by PLS regression analysis was 0.96, and the root mean square error of calibration （RMSEC） and root mean square error of cross validation （RMSECV） were 9.90 h and 11.39 h respectively. In prediction set, the R2 was 0.97, and the root mean square error of prediction （RMSEP） was 10.49 h. Conclusion The FTIR spectrum of the rat's spleen tissue can be effectively analyzed qualitatively and quantitatively by the combination of FTIR spectroscopy and data mining method, and the classification and PLS regression models can be established for PMI estimation.
ABSTRACT
Objective To summarize the key points of forensic medicine appraisal by retrospectively analyzing the scene.Methods The data of 193 homicide cases in a district of Weinan from 2007 to 2016 were collected and analyzed.Results The majority of the criminal suspect and victims was male,aged 21-40 years old,local,farmers and primary school educational level.Infringement was the majority criminal motivation (52.8％).The most common injuries tools were sharp instruments (63.8 ％);multiple parts damage accounted for 32.1 ％;mechanical injury induced hemorrhagic shock and craniocerebral injury were the most common causes of death in these cases (87.0％).Conclusions The demographic characteristics of suspects,criminal motivation,injury instruments,distribution of injuries and cause of death in the district of Weinan showed similar general characteristics,which could provide experience and reference for detecting homicide cases in the future.