The validation of 3D virtual comparison microscopy (VCM) in the comparison of expended cartridge cases.

In this study, the Cadre TopMatch-3D scanner and associated virtual comparison software was evaluated to determine whether this technique is a valid and reliable method of conducting cartridge component comparisons. That is, if virtual comparison microscopy (VCM) produces results at least equivalent to those generated through traditional light comparison microscopy (LCM), the method would be deemed valid for use in an operational setting. Particular emphasis was placed on the capability to render same source conclusions. Of the 40 true identifications available to each examiner, corresponding to a total of 520 comparisons, positive identifications were made more frequently using VCM as compared to traditional LCM where inconclusive conclusions were provided at a higher rate. VCM produced a higher sensitivity (88.41%) and specificity (13.64%) rate than LCM, 80.08% and 12.50%, respectively. Based on the findings of the study, considered together with the benefits that VCM offers in the name of efficiency, it became apparent that Cadre's 3D scanning microscope and its associated virtual comparison software tested in this study is an appropriate and valid technique for conducting comparisons of expended cartridge cases and can be implemented into routine casework for that purpose.

Latent fingermark development on fired and unfired brass ammunition under controlled and blind conditions.

There has been growing interest in the Foster+Freeman RECOVER® Latent Fingerprint Technology system to develop fingermarks from fired ammunition. Over a six-month period, 1540 fingermarks were deposited on brass.223 ammunition, the majority of which were then fired after different time intervals. Samples were subjected to a cleaning protocol and/or processed with disulfur dinitride, cyanoacrylate/Brilliant Yellow 40, and/or vacuum metal deposition. Overall, 121 out of 1304 (9.3%) of natural fingermarks deposited were deemed identifiable post-firing and processing. This translated to 102 out of 652 (15.6%) of fired cartridges having identifiable fingermarks. A pseudo-operational study, which involved processing 1000 fired brass ammunition of various caliber using disulfur dinitride with and without a cleaning protocol, was conducted; only 18 (1.8%) comparable fingermarks were developed. This study demonstrates the need for more robust research involving this challenging substrate and novel technology, with which several issues were identified.

Guidelines for the use and statistical analysis of the Home Office fingermark grading scheme for comparing fingermark development techniques.

This paper provides guidance on how to properly analyse data generated from the Home Office fingermark grading scheme. The core of the issue is that it creates ordinal data and should therefore not be analysed using averages. To reduce confusion, it is recommended to label the different degrees of fingermark development as classes rather than numerical scores. Appropriate statistical tests are provided to properly analyse Home Office fingermark grading scheme data, however, not using statistical tests is perfectly acceptable so long as conclusions are worded appropriately and do not exaggerate the significance of the findings. Some guidance is provided on estimating sample size and optimal methods for presenting results.

Building a ground-truth fingerprint dataset for proficiency testing and research.

This article outlines the process used to collect fingermarks in a controlled environment, encode, and store the fingermark images. It was important that the fingermarks resemble the type of evidence that would be found at a crime scene. This meant using a variety of substrates, development techniques, and residues. The dataset also includes non-mates; the manner in which close non-matches were found using an Automated Fingerprint Identification System (AFIS) will be discussed. An efficient workflow was created which allowed the RCMP to capture 3011 fingermark images from 62 individuals. This is the foundation of the dataset that will be used for future research and proficiency testing by the RCMP. Two vital lessons learned during the process were, the importance of thoroughly cleaning objects before use and to ensure proper quality control checks were in place, including verification through a fingerprint comparison. Since the data is being used in proficiency testing, it is currently unavailable for public use.