| The scientific reliability of firearms identification has been challenged in the last twenty years,including the lack of a representative database for this subject.With the rapid development of automatic identification technology,firearm examiners have conducted numerous researches with the automatic ballistic identification system as responses to the relevant disputes.Similar challenges also need to be overcome in domestic firearm identification work containing the identification of registered firearms.Due to the large number of registered firearms,the microscopic examination used by the firearm examiners is relatively inefficient and subjective,so the development trend is to establish a digital registered ballistic database.A registered ballistic database of Chinese Norinco QSZ-92 pistols with registered ammunition was established and its accuracy and implementation were evaluated through the Evofinder?system in this paper.To assess the performance of the registered ballistic database,1,000 Chinese Norinco QSZ-92 registered pistols from Beijing Municipal Public Security Bureau were selected and the registered ammunition of each pistol were also collected,including three fired bullets and three cartridge cases.Except four severely deformed bullets fired from four pistols and one missing cartridge case,all fired bullets and cartridge cases from each pistol were scanned by the automated ballistic identification system Evofinder?.That is 2,996 bullets and 2,999 cartridge cases in total.The bullets labeled with“B1”and the cartridge cases labeled with“C1”were randomly chosen from each pistol's three ammunition and then correlated against the rest of the2,995 fired bullets and 2,999 fired cartridge cases respectively,and the correlation results?including bullets and cartridge cases?of the 1,000 registered pistols were collected.Besides,50“B1 bullets”and 50“C1 cartridge cases”were randomly selected and correlated against randomly composed databases of 30,150,300,600,1200,1800,and 2400 records,and the correlation time and results for each comparison were analyzed by Minitab?17 and MedCalc?18.Based on the correlation results of 1,000 bullet and 1,000 cartridge case,both known matches were found in the top 2 rankings in each list?100%?.On the whole,the similarity scores of the known matches were distributed with higher scores than those of known non-matches generally.In a correlation list,the similarity score of known matches were generally“outstanding”.In addition,as the size of the database increased:on the one hand,the average time for correlation increased and the standard deviation increased as well;on the other hand,the known matches were consistently at the top of the correlation list,while the rankings of known non-matches showed a linear growth,and the similarity scores of known matches and known non-matches did not change.Based on this behavior,an extrapolation of the average correlation time and correlation results in a larger or smaller database could be roughly estimated.The implementation of a registered ballistic database based on Chinese Norinco QSZ-92pistols was proven to be accurate,effective,efficient and convenient for forensic firearms examination in this paper.The result of the experiment could serve as a reference for the digital archive of Chinese Norinco QSZ-92 pistols.Besides,the difference of firearms marks within1,000 Chinese Norinco QSZ-92 registered pistols were also illustrated in various quantitative forms through Evofinder?system,which could provide the basic experimental support for the examination of the individuality of firearms marks. |
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