Framework of techniques for developing latent fingermarks from fired cartridge cases and brass metal plates in Ghana

Abstract

Firearm-related injuries resulting from firearm-related crimes such as homicide, suicide, accidental gun firing, and armed robbery have been a persistent and chief cause of mortality across all age groups globally. For example, an estimated 18,000 people aged 17 years and below in the United States die annually from firearm-related crime. In South Africa’s KwaZulu-Natal province, about 19%, representing 4,087 out of 22,910 of all deaths, were ascribed to firearm-related injuries. Only 1.7% (n = 90) of firearm-related fatalities were recorded in Ghana following 5359 autopsies conducted between 2008 and 2013. The commonly encountered forensic evidence in such firearm-related scenes comprises fired cartridge cases, unfired cartridges, fired projectiles (bullets), and often firearms. During crimes involving firearms, it is not uncommon for the perpetrator to leave behind their fingermarks on the firearm and cartridge case. The ability to develop latent fingermarks on these challenging fired cartridge cases can be crucial in resolving crime cases and advancing forensic investigations and human identification. Despite the success in a few forensic cases, the recovery of identifiable fingerprints with continuous ridges on fired cartridge cases remains challenging. Furthermore, there is a current lack of agreement on the most efficient standalone or sequential fingermark detection technique to use for recovering fingermarks from fired and unfired cartridge cases in real-life case scenarios. The main objective of the study was to compare and establish a framework of techniques for developing latent fingermarks from fired cartridge cases and brass metal plates in Ghana. The specific objectives of the study were to: 1. determine the ability of an optimised locally made fuming chamber in developing latent fingerprints from fired cartridge cases, and brass metal plates; 2. determine an optimal framework of techniques for developing latent fingermarks on fired cartridge cases; 3. compare the efficiency of three different sets of sequential fingermark detection techniques for developing latent fingermarks on fired cartridge cases and brass metal plates; 4. determine the impact of age since fingermark deposition on the development of latent fingermarks on fired cartridge cases; and 5. determine the best-acidified hydrogen peroxide formulations for visualising fresh and aged latent fingermarks from brass metal plates. A quantitative research design (exploratory design) was employed to investigate the capabilities of different fingermark detection techniques for enhancing latent fingermarks on fired cartridge cases and brass metal plates. The study was conducted at the Department of Forensic Sciences Laboratory at the University of Cape Coast (UCC), Cape Coast, in the Central Region of Ghana. The simple random sampling technique was employed to recruit fifteen (n = 15) participants (fingerprint donors) for the study. Only participants with 10 normal fingers and without any form of deformation or injury were included in the study. Five (5) different calibers of brass ammunition were purchased and used as substrates for the study. Natural latent fingermarks were obtained from all the eligible participants. To achieve this, the fingermark donors were instructed to first wash their hands thoroughly with soap and water and then resume their normal routine for exactly 30 minutes prior to donating their fingermarks on the selected ammunition. The cartridges to be fired were randomly selected from their original boxes without undergoing any form of preparation (such as precleaning). The assigned fingermark donors were guided to deposit their natural latent fingermark (from the right thumb) on the cartridge cases before it was carefully loaded into the firearm’s magazine for the firing process by a certified armorer. A homemade cyanoacrylate fuming chamber with dimensions 48 mm × 28 mm × 82 mm was used for the cyanoacrylate fuming process. The cyanoacrylate fuming was performed at room temperature and ambient pressure using 5 drops of local super glue known as the “Everbond cyanoacrylate adhesive” (with batch number 202010001) at a developing time of 45 minutes. Following the cyanoacrylate fuming process, the developed prints were subsequently enhanced using other fingermark detection techniques in series, such as fluorescent dyeing (with Ardrox (AR), Rhodamine 6G (R6G), Basic Yellow 40 (BY40)), and acidified hydrogen peroxide (AHP). The developed fingermarks following each set of enhancement techniques on the casings were first visually examined using a magnifying lens by the researcher. Blinded grading was further performed by an independent fingerprint examiner (with over 10 years of working experience in fingerprint science) at the UCC, Ghana. The independent examiner was not involved in any part of the present study. The fingermark grades recorded by the two examiners were in resonance. The graded fingermarks were photographed using a Canon EOS Rebel T7 digital single-lens reflex (DSLR) camera with an appropriate alternative light source (ALS) and viewing filter. The Home Office fingermark grading scheme, with suggested modification, was adopted as the scale to assess and grade the quality of the developed fingermarks in the present study. It bears noting that the grading was done for the enhanced fingermarks on the cartridge cases directly and not on the photographed images. The scores for each developed fingermark were manually entered into Microsoft Excel running on Windows 16 for data visualization. Although the grading scale was numerically presented, each numerical value (class) denotes a label that is arbitrary and categorical. The result for each category was presented in frequencies and illustrated with the aid of a bar graph. Ethical approval (Reference number: 4198) was obtained from the College of Law Research Ethics Review Committee (CLAW_RERC) of the University of South Africa (UNISA). Written informed consent was sought from all participants after the purpose of the study was explained, before recruiting them for the study. The results of the study disclosed that the homemade cyanoacrylate fuming chamber showed exceptional efficiency in the development and visualisation of latent fingermarks, yielding significantly enhanced fingerprint images on all substrates (fired cartridge cases and brass metal plates). Latent fingermarks were successfully developed on the fired cartridge cases and the brass metal plates, with the resulting fingerprint patterns displaying high contrast and fine ridge detail (Score of 3 on fired cartridge cases and 4 on the brass metal plates). The sequential application of cyanoacrylate (CA) fuming, followed by Basic Yellow 40 (BY40), and acidified hydrogen peroxide (AHP), was the most effective technique for developing fingermarks aged for 1 day, 7 days, and 14 days on the fired cartridge cases. This was followed by the sequential application of cyanoacrylate fuming, followed by rhodamine 6G, and AHP (CA + R6G + AHP), and the least efficient was cyanoacrylate fuming,followed by ardrox, and AHP (CA + AR + AHP). The results of the current study disclosed a consistent and expected relationship between time elapsed since fingermark deposition and the quality and frequency of the latent fingermark recovered. Using the CA + BY40 + AHP development technique, the results showed that the recovery rate of latent fingermarks was highest at one day after deposition, decreased slightly at seven days, and was lowest at fourteen days. This finding was consistent when CA + R6G + AHP and CA + AR + AHP were employed for the development of aged latent fingermarks from all spent cartridge cases. The findings also revealed that AHP formulations 1, 3, and 5 had a greater prospect of developing successive latent fingermarks on brass metal plates. The efficiency of the five different formulations was recorded in the order: formulation 3 >formulation 1, and formulation 4 > formulation 2 > formulation 5. The findings of this study provide significant advancements in forensic fingerprint development on fired cartridge cases and brass metal surfaces. By designing a cost-effective, homemade fuming chamber, forensic practitioners, particularly in resource-limited settings, can now have an affordable and efficient method for developing latent fingerprints. Additionally, the study highlights the effectiveness of sequential chemical treatments, such as Basic Yellow 40, Ardrox, and acidified hydrogen peroxide, in enhancing fingermark visibility after cyanoacrylate fuming. These techniques provide forensic experts with alternative approaches for improving ridge detail clarity, especially when initial fuming results are suboptimal. The findings of this study highlight the need for further research into the long-term stability and chemical interactions affecting latent fingermarks on brass metal surfaces.