The Examination Of Soil Evidences And Research On Data Statistical Methods In Forensic Science

Soil widely exists in people's daily lives,even in today's highly urbanized areas,people still have a high probability of being exposed to soil material every day.When a criminal comes into contact with soil,the probability of soil evidence transferring from the crime scene to the tools of the crime,the victim body,and the body of the suspect increases.Comparing the collected soil samples allows investigators to correlate the case with the suspect or rule out the suspect,which makes soil evidence a more common type of trace evidence in forensic science.Till now,effective and efficient detection methods have been developed in soil evidence examination.But what is not commensurate with the development of identification technology is that the interpretation of soil evidence data,and no classification comparison standard has yet been established,which has greatly limited the application of soil evidence in case detection and the court trial.In order to solve the above problems encountered in the development of soil evidence examination,this article measured the content of the common elements in the soil samples extracted from different places through experiments,and selected the data interpretation methods for comparison and classification examination between soil samples.A total of 584 soil samples were collected from ten cities including Kunming,Guangzhou,Fuzhou,Hohhot,Jinan,Beijing,Changchun,Wuhan,Xi'an,and Lanzhou.The X-ray fluorescence spectrometry method most commonly used in domestic soil evidence examination was chose to measure the content of ten major common elements such as Al,Si,Fe,K,Na,Mg,Ca,P,Mn,and Ti in soil samples,and then this article analyzed the statistical methods that were most suited for the interpretation of elemental data from soil samples.The series of data measured by instrumental were screened and verified firstly.Then the common statistical methods in chemometrics including mean analysis,cluster analysis,principal component analysis and discriminant analysis were used to analyze the soil samples data.The likelihood ratio test method which had been generally recognized in the international counterparts was tried to analyze the XRF data.The kernel density function was used to improve the likelihood ratio method accuracy.Comparison of the advantages and disadvantages between various analysis statistical methods,it was concluded that the likelihood ratio method was superior to other traditional data analysis methods.Finally,the development direction of future data analysis in the field of soil evidence examination was put forward,and the methods of new indicators incorporated and the application of support vector machines in the field wereexplained briefly.