Volume 23. Number 1
December 2024

Original Articles

 Lea Hui Lim, Ph.D.; Ahmad Fahmi Lim Abdullah,  Ph.D.; Kah-Haw Chang, Ph.D.

Abstract： Gunshot residues (GSR) produced from different ammunitions upon firing using the same firearm could be varied according to the compositional ingredients used to make the propellant powder. Due to the introduction of non-toxic ammunition, the conventional detection of lead, barium and antimony has also reported obstacles for the confirmative determination of GSR. In such cases, the organic profiles of GSR could serve as the supporting evidence to prove a firing activity and to differentiate the ammunitions. This study was aimed to profile the organic GSR from spent cartridge cases by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) for forensic comparison. In this study, eleven spent cartridges were subjected to SPME-GC-MS and the chemical attribution signatures in each profile were identified. Subsequently, the organic GSR profiles across various ammunition types were compared, and a screening methodology for classification of GSR profiles was proposed. Our SPME-GC-MS analysis on the spent cartridge cases had detected five key compounds, namely the diphenylamine, dibutyl phthalate, ethyl centralite, tributyl acetylcitrate, and butyl citrate, that possessed important roles in propellant powders. Comparison of organic GSR profiles revealed the choice of stabilisers and plasticisers used were found to be varied among manufacturers. Based on the proposed screening methodology, five distinct categories were formed. By applying such screening methodology, unknown samples could be associated with potential ammunition types or distinguished based on the specific sources. To conclude, the study had successfully profile the organic GSR from spent cartridge cases, and the screening method could serve as a useful tool to classify and distinguish GSR samples, assisting forensic investigation in criminal cases involving firearm.

Keywords: Gunshot residue, spent cartridge cases, organic gunshot residue, solid phase microextraction (SPME), gas chromatography-mass spectrometry (GC-MS).

The Influence of Reduced Powder Charge on the Forensic Examination of Fired Cartridge Cases

Wen-Nan Yu, M.Sc.; Hsien-Hui Meng, Ph.D.

Abstract： It is currently impossible for domestic forensic laboratories to determine the wounding potential of a questioned firearm unless the weapon is seized. To break through this limitation, we conducted a series of firing tests utilizing one short recoil operated pistol and one gas-delayed blowback pistol and cartridges with varied amounts of powder charge. The muzzle velocity (v) and energy density (ED) of the fired bullets were determined based on a ballistic chronograph. The breechface marks, firing pin aperture marks, firing pin aperture shear marks, and chamber marks on fired cartridge cases were examined. The results indicated that the ED and the distribution length (L) of striated chamber marks were proportional to the amount of powder charge. And the ED was also proportional to the barrel length of fired pistol. Correlation analysis revealed that L was linearly correlated with logarithm transformed value of ED (ln ED). The coefficient of determination (R²) between L and ln ED was greater than 0.99. Two-variable linear equation was used to calculate the evaluated energy density (ED_E). Verification firing tests were conducted using one blowback pistol and seven rounds of reducing-powder-charged cartridges. To calculate ED_E, we employed L and the linear equation. The percentage differences between ED and ED_E were all less than 3.5%. These results demonstrate that the method developed in this study is effective and practical for evaluating the wounding potential of a questioned firearm through the examination of cartridge cases fired from it. 

Keywords: firearms examination, reduced powder charge, breechface marks, firing pin aperture marks, firing pin aperture shear marks, chamber marks, muzzle energy density

Wounding Potential Evaluation of Low-power Weapons via Ballistic-soap Deformation

Wen-Nan Yu, M.Sc.; Hsien-Hui Meng, Ph.D.

Abstract：  Miscellaneous firearms that capable of firing metal projectiles to inflict penetrating injuries are regarded as controlled weapons in Taiwan. Aluminium witness plates have been used to evaluate the wounding potential of airguns by local crime laboratories. In this study, the entrance diameters (d), penetration depths (D), and volumes (V) of gunshot cavities in ballistic soaps were used to evaluate the muzzle energy density (ED), and hence the wounding potential, of airguns and unmodified blank pistols. A series of firing tests were conducted using two airguns and two types of projectiles. The velocity (v), kinetic energy (KE), and energy density of the projectiles fired at ballistic soaps were determined using a ballistic chronograph. The results of correlation analysis between the mean values of d and v, D and ED, and V and KE, respectively, showed that the coefficients of determination (R²) ranged 0.9411 to 0.9991. The results of verification firing tests using airguns and unmodified blank pistols demonstrate that the linear equations obtained to model the relationship between the mean values of d and v, D and ED, and V and KE, respectively, were all useful for calculating the evaluated impact energy density (ED_E) and the percentage differences between ED and ED_E were found to be ≤ 16.8%, 2.8%, and 11.5%, respectively. The results also indicate that V is more suitable than d and D for use in the firing tests to evaluate the wounding potential of low-power weapons. Additionally, we developed a non-destructive, fast, accurate, and costless method to determine the volume of gunshot cavity in ballistic soap. The results in this study are expected to assist crime laboratories in determining the legal status of low-power weapons with respect to the legal power limit of controlled firearms. 

Keywords: firearms examination, airgun, blank pistol, ballistic soap, temporary cavity volume, impact energy density, wounding potential

Transference of Fingerprint between the Adhesive Side of an Adhesive Tape and Ziplock Bag

Wee-Beng Lim, M.S.; Chun-Chieh Chen, Ph.D.; Eugene Lee, M.S.; Wei-Ling Stella Tan, M.S.

Abstract：  Adhesive tapes, including duct and insulation tapes, and Ziplock bags are common packing materials for illicit drugs, such as diamorphine, methamphetamine, and cocaine for distribution purposes. These illicit drugs are often packed in Ziplock bags and taped with adhesive tapes into bundles, usually to avoid detection, before they are moved down the supply chain to consumers. When a drug bundle is seized by law enforcement agencies such as the Central Narcotics Bureau in Singapore, fingerprint and deoxyribonucleic acid (DNA) analyses are commonly deployed by investigators or forensic specialists to determine who touched and/or possessed the drug bundles. However, due to the destructive nature of these two forensic tools, investigators often perform DNA analysis over fingerprint analysis even though the presence of fingerprint evidence on the tapes, especially on the adhesive side, is highly incriminating. The present study examines the transference of fingerprints between a tape’s adhesive side and a Ziplock bag’s surface. Our findings conclusively showed that fingerprints could be transferred between the tape’s adhesive side and Ziplock bag’s surface. Moreover, retrieving useful prints for examination from the tape’s adhesive side using the Wet Powder™ method is more likely to achieve better quality prints. If the lifted print had an identical minutiae pattern with the reference print, it was considered a print directly deposited onto the surface, whereas if the lifted print had a symmetrical minutiae pattern as compared to the reference print, it was considered a print that was transferred from the opposing surface.

Keywords: forensic science, fingerprint, transference, adhesive tapes, transferred, DNA