Small particle reagent (SPR) is a technique performed to detect latent fingerprints left on wet and moist surfaces based upon the reaction between fatty acid residuals present in the traces and hydrophobic tails of the specific reagent. Those tails are linked to a hydrophilic head of zinc carbonate based formulation to give coloured precipitate. In the present study, we have prepared a novel SPR formulation constituting of zinc carbonate based on basic fuchsin dye for development of latent fingerprints on wet surfaces. It was shown to develop clear, sharp and detailed fingerprints on non-porous surfaces after these were immersed in water for up to 45 days. The ability of the present formulations to detect weak and chance prints not only enhances its utility, but also its potentiality in forensic case work investigations. The raw materials used to prepare the SPR are cost-effective and non-hazardous. ª 2015 Hosting by Elsevier B.V. on behalf of The International Association of Law and Forensic Sciences (IALFS).
Small particle reagent (SPR) is a widely used method for developing latent fingerprints on non-porous wet surfaces. SPR based on zinc carbonate hydroxide monohydrate, ZnCo 3 AE 2Zn(OH) 2 AEH 2 O -also called basic zinc carbonate -has been formulated. The other ingredients of the formulation are crystal violet dye and a commercial liquid detergent. The composition develops clear, sharp and detailed fingerprints on non-porous items, after these were immersed separately in clean and dirty water for variable periods of time. The ability of the present formulation to detect weak and faint chance prints not only enhances its utility, but also its potentiality in forensic case work investigations. The raw materials used to prepare the SPR are cost-effective and non-hazardous.ª 2014 Production and hosting by Elsevier B.V. on behalf of Forensic Medicine Authority.
Abstract
Simulations of free-flight trajectories of seven different 7.62mm/.308 rifle bullets (designated B0-B6) have been carried out by the numerical solution of the equations of motion. The average drag force coefficients (CD) for B0-B6 have been calculated by scaling the variation of CD with the Mach number of flight with reference to the G7 standard projectile. The Point-Mass trajectory model and its Flat-Fire approximation have been studied with and without the effect of range winds. The solutions of the systems of equations have been carried out by writing scripts in the Python programming language. It is observed that an increase in the bullet weight and consequently the sectional density lowers the CD. Furthermore, a hollow-point adds to the drag, while a plastic tip on the bullet reduces the drag, when compared to a FMJ or Spitzer bullet. As expected, it is seen that the bullet with the highest drag (B0) has the shortest range and lowest apogee, while lower drag bullets fly further and higher. The crossover of trajectories is observed at ~30 angle of gun elevation, which implies that the maximum range is not achieved when fired at 45, as is the case with vacuum trajectories. Flat-fire approximation of the point-mass model was also solved to observe trajectories and crosswind deflections of the bullets when fired at 5 angles of elevation. The simulated trajectories exhibit rigid trajectory behaviour about the origin/gun muzzle.
Polycarbonate is widely used as structural material due to its extreme resistance to impact and perforation. In a crime involving firearms, the bullet may impact various objects fitted with or made of polycarbonate sheets leaving high chances of discovering the fractured PC sheets and fragments at the scene of crime hence these objects may become objects of the criminal investigation. In the present work the perforation pattern of PC sheets of thicknesses 8mm, 10mm, 12mm and 15mm at firing ranges 5m and 10m when impacted against 9×19mm Full Metal Jacket (FMJ) bullet were examined. It was observed that after impact the PC sheet develops entry hole smaller than the calibre of bullet; formation of crack zone, plastic zone; and petalling on the distal face were observed. It was found that as the thickness of the sheet increases, the diameter of the entry hole increases. The diameter of the exit hole initially increases and then becomes constant. At 5m range of fire the trend of crack zone becomes nearly constant from 8mm to 15mm thickness, however, at 10m range of fire crack zone increases from 8mm to 15mm thickness. Furthermore, the diameter of plastic zone increases as the thickness of the sheet increases (from 8mm to 15mm respectively).
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