The role and significance of the likelihood ratio concept in assessment and interpretation of the results of forensic activities

A brief review on using the Bayesian concept of the likelihood ratio (LR) in forensic activities is presented. It is proved that the use of the likelihood ratio provides assessing the measure of uncertainty regarding the truth or falsity of the assumption of expertise when taking into account a priori chances and new information appearing in the course of expert research. A possible simulation experiment is presented as an example to calculate a set of the likelihood ratio values from the validation database for forensic examination of sound recordings. Different approaches of using the likelihood ratio in assessing the trueness of the judicial evidence are considered. The concept of the likelihood ratio has been adopted as the standard procedure for different types of examinations used in the laboratory practice, including that of the European network of forensic institutes (ENFSI).