Construction and Evaluation of the Database for Likelihood Ratio Evaluation of Fingerprint Evidence
The establishment of a scientific quantitative evaluation system for fingerprint evidence,especially how to introduce the statistical method of likelihood ratio into the digital representation of fingerprint identification,is a hot issue in the current theoretical and practical research of forensic science.The construction of a scientific and effective likelihood ratio evaluation model for fingerprint evidence requires rich same-source and different-source fingerprint databases to obtain the likelihood function with a stable distribution law,thus,the quality of the same-source and different-source databases directly affects the performance of the likelihood ratio model.By using the live-scan fingerprint collector and screen recording software to obtain more than 1 000 distorted fingerprint images for each fingerprint in different distortion modes,a total of 200 000 same-source fingerprints are obtained from 200 simulated fingerprints,which constitutes the same-source fingerprint database;and the different-source fingerprint database consists of ten million people's ten-fingerprint database in policing practice.On this basis,the automatic fingerprint identification system is utilized for query and comparison,and the comparison score data are evaluated.The experimental results show that the fingerprint data of different distortion modes have significant differences;the degree of pressure and the impressing time have little effect on the comparison scores of fingerprints.From the results of statistical analysis of the total number of samples and the subsample data after different degrees of reduction,it can be seen that the number of same-source samples of each fingerprint can still form a stable distribution law when the number of fingerprints is as few as 155.Therefore,the database we built is rich in the number of same-source and different-source fingerprints,reasonable in structure,and has the data basis for forming a stable distribution law,which is helpful for the subsequent establishment of the likelihood ratio evaluation model.
万方数据
维普
