In recent years,many studies have been conducted in the field of firearm identification with the objective of providing an objective method of evaluating the comparison of cartridge cases.However,less attention has be...In recent years,many studies have been conducted in the field of firearm identification with the objective of providing an objective method of evaluating the comparison of cartridge cases.However,less attention has been paid to the objective evaluation of bullet comparisons.In this study,1000 registered Chinese Norinco QSZ-92 pistols were used,and a database of 2996 bullets was constructed.Both the receiver operating characteristic(ROC)curve and the score-based likelihood ratio method were used to objectively evaluate the similarity scores derived by the EvofinderVR system.The results indicate that this system has excellent ability to discriminate between the selected pistols.This paper proposes an objective evaluation method,which serves as a response to the ongoing debates regarding the foundation of the discipline.展开更多
The specificity of marks was evaluated by differences between marks left by the same firearm(within variability)and differences between marks left by different firearms(between variability).The within variability and ...The specificity of marks was evaluated by differences between marks left by the same firearm(within variability)and differences between marks left by different firearms(between variability).The within variability and between variability of firing pin impressions and breech face marks on cartridge cases from over 3070 consecutive firings of a Chinese Norinco QSZ‑929 mm pistol were investigated based on the automated ballistic identification system Evofinder®.The first 20 cartridge cases and one random specimen out of every set of 10 consecutive cartridge cases of the remaining 3050 cases were entered into the Evofinder®system.Thus,325 cartridges fired from the same pistol were used to estimate the within variability.Then,88 cartridges fired from 88 different pistols of the same model(one cartridge each)were used to estimate the between variability.This study established a database containing 413 cartridges.We used the 325 cartridges fired from the same pistol as a correlation baseline in the database.Both firing pin and breech scores and gaps between these scores were used to analyze the variability.In the score evaluation process,a likelihood ratio system was used to evaluate the likelihood ratio performance.The Evofinder®system correctly discriminated the matches,and the likelihood ratios provided strong support for the true state of the hypothesis.In addition,we found that the score gap was usually greater than the other score differences by more than 1000%in firing pin list and 100%in the breech list.Further analysis of the score and gap can help examiners use the Evofinder®system more efficiently.展开更多
基金This study received funding from the Opening Project of Shanghai Key Laboratory of Crime Scene Evidence[grant number 2018XCWZK18].
文摘In recent years,many studies have been conducted in the field of firearm identification with the objective of providing an objective method of evaluating the comparison of cartridge cases.However,less attention has been paid to the objective evaluation of bullet comparisons.In this study,1000 registered Chinese Norinco QSZ-92 pistols were used,and a database of 2996 bullets was constructed.Both the receiver operating characteristic(ROC)curve and the score-based likelihood ratio method were used to objectively evaluate the similarity scores derived by the EvofinderVR system.The results indicate that this system has excellent ability to discriminate between the selected pistols.This paper proposes an objective evaluation method,which serves as a response to the ongoing debates regarding the foundation of the discipline.
基金This work has received funding from the Opening Project of Shanghai Key Laboratory of Crime Scene Evidence(2018XCWZK18).
文摘The specificity of marks was evaluated by differences between marks left by the same firearm(within variability)and differences between marks left by different firearms(between variability).The within variability and between variability of firing pin impressions and breech face marks on cartridge cases from over 3070 consecutive firings of a Chinese Norinco QSZ‑929 mm pistol were investigated based on the automated ballistic identification system Evofinder®.The first 20 cartridge cases and one random specimen out of every set of 10 consecutive cartridge cases of the remaining 3050 cases were entered into the Evofinder®system.Thus,325 cartridges fired from the same pistol were used to estimate the within variability.Then,88 cartridges fired from 88 different pistols of the same model(one cartridge each)were used to estimate the between variability.This study established a database containing 413 cartridges.We used the 325 cartridges fired from the same pistol as a correlation baseline in the database.Both firing pin and breech scores and gaps between these scores were used to analyze the variability.In the score evaluation process,a likelihood ratio system was used to evaluate the likelihood ratio performance.The Evofinder®system correctly discriminated the matches,and the likelihood ratios provided strong support for the true state of the hypothesis.In addition,we found that the score gap was usually greater than the other score differences by more than 1000%in firing pin list and 100%in the breech list.Further analysis of the score and gap can help examiners use the Evofinder®system more efficiently.
