Research on likelihood ratio evaluation method of fingerprint evidence based on parameter estimation method

Abstract

Fingerprints with similar morphological characteristics but from different individuals can lead to errors in individual identification, especially when dealing with large databases containing millions of fingerprints. To address this issue and enhance the accuracy of similar fingerprint identification, the use of the likelihood ratio (LR) model for quantitative evaluation of fingerprint evidence has emerged as an effective research method. In this study, the LR fingerprint evidence evaluation model was established by using mathematical statistical methods, such as parameter estimation and hypothesis testing. This involved various steps, including database construction, scoring, fitting, calculation, and visual evaluation. Under the same-source conditions, the optimal parameter methods selected by different number of minutiae are gamma and Weibull distribution, while normal, Weibull, and lognormal distributions were the fitting parameters selected for minutiae configurations. The fitting parameters selected by different number of minutiae under different-source conditions are lognormal distribution, and the parameter methods selected for different minutiae configurations include Weibull, gamma, and lognormal distributions. The results of the LR model showed increased accuracy as the number of minutiae increased, indicating strong discriminative and corrective power. However, the accuracy of the LR evaluation based on different configurations was comparatively lower. In addition, the LR models with different numbers of minutiae outperformed those with different minutiae configurations. Our study shows that the use of LR models based on parametric methods is favoured in reducing the risk of fingerprint evidence misidentification, improving the quantitative assessment methods of fingerprint evidence, and promoting fingerprint identification from experience to science.

Key points: Likelihood ratio (LR) method based on parameter estimation was applied to scientific evaluation of fingerprint evidence with excellent discriminatory and calibration capabilities.Both the number of minutiae and configuration of minutiae have significant effects on the score-based LR method.Fingerprints from the same source contain many different patterns of deformation.Databases containing 10 million fingerprints from different sources have been used for building the LR model.

Keywords: evidence evaluation; fingerprints; hypothesis testing; likelihood ratio; parameter estimation; quantitative method.