Conventional development of latent fingerprints is compromised when the prints are decomposed by extreme temperatures, such as those encountered when a weapon cartridge is fired, an improvised explosive device is detonated, and/or in arson cases. Understanding how these extreme temperatures alter the chemical and physical properties of latent fingerprint residue could aid in the discovery of a reagent that could effectively develop these decomposed fingerprints. To mimic scenarios where fingerprints may be exposed to high heat conditions, standards of the five most abundant amino acids in fingerprint residue as well as extracted fingerprint residue were pyrolized under controlled conditions. Compounds identified as pyrolytic decomposition products were 3,6-dimethylpiperazine-2,5-dione (from alanine), maleimide, and 2,5-furandione (from aspartic acid). The pyrograms and selected ion traces show these products to hold promise as indicators of decomposed fingerprint residues and, therefore, may serve as good candidate substrates for a developing reagent.

This paper presents a combined DWT and LSB based biometric watermarking algorithm that securely embeds a face template in a fingerprint image. The proposed algorithm is robust to geometric and frequency attacks and protects the integrity of both the face template and the fingerprint image. Experimental results performed on a database of 750 face and 750 fingerprint images show that the algorithm has the advantages of both the existing DWT and LSB based algorithms. A multimodal biometric algorithm is used as a metric to evaluate the combined performance of both face and fingerprint recognition.

The forensic science pattern comparison areas, including fingerprints, footwear, and firearms, have been criticized for their subjective nature. While much research has attempted to move these disciplines to more objective methods, examiners are still coming to conclusions based on their own training and experience. To complement this subjectivity, black box studies are necessary to establish the accuracy of these featurecomparison methods. However, when cartridges are fired by a firearm to create cartridge case test sets there may be significant variability within the resulting impressions. This can result in different participants receiving test sets with varying levels of difficulty based on differences in impression quality. Therefore, comparison of accuracy between examiners is not straightforward. To compare accuracy between examiners, a method called double-casting was used to create plastic cartridge case reproductions. Double-casts of twenty-one test sets of master cartridge cases were created and mailed to firearm examiners. The double-casts ensured that all participants were comparing exhibits with the same level of detail. The examiners were tasked with determining if the unknown cartridge case in each set was fired by the same firearm as the three knowns. Automated comparisons were also used to compare the cartridge cases within each set. The results from this study showed that there are differences in examiner conclusions when examining the same evidence. Furthermore, it was shown that automated comparison metrics would benefit examiners as a quality control measure to correct any potential errors and strengthen conclusions. K E Y W O R D Sblack box study, breech face, cartridge case variability, congruent matching cells, doublecasting, error rates, firearm tool mark, firearms identification Highlights• Comparison accuracy was analyzed between examiners using cartridge case double-casts.• Automated comparisons were performed to compare to the examiner conclusions.• Variability in examiner conclusions when evaluating the same evidence was observed.• Automated methods would fit well into the comparison process as a quality control measure.

Due to the shot-to-shot variability in tool mark reproduction on fired cartridge cases, a method of replication is needed for the creation of training and testing sets. Double-casting is one method that has been used for this application, but the accuracy and variability of this method needs to be characterized. Three firearms were used to fire 25 cartridges each to create the master cartridge cases. The double-casting method consists of creating a silicone mold of the master cartridge case. A plastic resin mix is then poured into the mold to create the double-cast reproduction. Fifteen double-casts of each of the 75 fired cartridge cases were created across different silicone molds to analyze withinand between-mold variability. The master cartridge cases and double-casts were scanned with a confocal microscope (Sensofarâ S neox) to create three-dimensional representations of the surfaces. Two similarity metrics were used for the objective comparison of the double-casts to their master cartridge cases: the areal correlation coefficient (ACCF MAX) and the number of congruent matching cells (CMC). The ACCF MAX and CMC data, along with visual examinations, showed that the double-casting method produces accurate reproductions. Within-mold variability was found to be minimal, and between-mold variability was low. These results illustrate that double-casting can be applied for training and testing purposes.

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