Abstract. The vacuum vaporization technique is widely used to develop of visualized latent fingerprints on substrate surface for forensics investigation. In this study, we reported the first utilization of lawsone in the vacuum vaporization technique. The lawsone was sublimation in vacuum and showed the detected latent fingerprints on thermal papers. The method involves hanging the thermal paper samples 5, 10, 15 cm above a heating source with dispersed lawsone solids in a vacuum chamber. The optimized condition for lawsone sublimation are 50, 100, 150 mg with low-vacuum (0.1 mbar) and vaporizing temperature at 40-60°C. The sample fingerprints were left for 1, 3, 7 and 30 days before examination comparison between lawsone and fingerprint ink pad using an Automated Fingerprint Identification (AFIS). The resulted showed that using 100 mg lawsone sublimation on thermal paper at the range of 10 cm evidenced the clear, detectable minutiae which can be used for visualization and identification of latent prints without the background black staining known. Thus, this study might be interested application for developing latent fingerprints as a solvent free technique and non-hazardous materials. IntroductionThe vacuum vaporization is a technique of thin-film deposition in which the metals were brought into the gas phase by thermal sublimation and deposited to the surface of substrate for a thin film. This process is widely used in the semiconductor, microelectronic and optical industries. Currently, this technique is applied for visualized latent fingerprints as known as Vacuum Metal Deposition (VMD) [1][2][3][4]. For example, gold was deposited on polyethylene substrates to develop fingerprints [5], copper and gold can deposit on the polymer banknotes to visualize latent fingerprints [6] and gold/Zinc VMD was also successful to visualized the fingerprints on fabrics [7]. Moreover, the organic chemicals were also succeeded to develop latent fingerprints instead of metals e.g. the use of solid ninhydrin used develop the latent fingerprints on porous surface [8]. Thus, the organic chemicals that can undergo thermal sublimation and visualization are of interest to study for the vacuum vaporization. Lawsone is a naphthoquinone natural products from the leaves of Lawsonia inermis has been used as a skin and hair dye as its reacts with amino acids of keratin. The lawsone solution can also react with latent fingerprint deposits on paper surfaces to show purple-brown impressions of ridge details which are also photo luminescent [9]. Detection of latent fingerprints on thermal paper is an
Thermal paper is a special type of paper that is coated with chemicals on the paper layer to change color when exposed to heat. When discovering fingerprints by using chemical reagents such as ninhydrin solution with thermal paper, it shows black staining background on the heat-sensitive front side. Thus, the latent fingerprints cannot be discovered. In this study, we have reported the first utilization of ninhydrin with water glue in different ratios for the development of latent fingerprints on the thermal papers. The results showed that at 0.020-0.060 g/mL of water glue in ninhydrin solution reduced the black strain after tested with thermal paper and made the appearance of the fingerprint more clearly. So, the detectable minutiae can be used for visualization and identification of latent prints. Using an Automated Fingerprint Identification System (AFIS), it is showed between 59-87 points of minutiae. As the results, this method could be used as an alternative method to developing latent fingerprints with non-hazardous materials, reduce costs and easy to find.
The bullet hole traces from both entrance and exit at the crime scene are important data which can be used in the investigation. Most of the analytical investigation will be mostly considerably on the physical appearance e.g. tear, traces of gunshot, the size of the entrance and exit bullet holes. The purpose of this research was to study the pattern and the difference of marks on the metal target caused by the collision of gunshots using 4 types labeled as A is Full Metal Jacketed (FMJ) 135 gr. of Thai Arms., B is Jacketed Hollow Point (JHP) 230 gr., C is Full Metal Jacketed (FMJ) 230 gr. and D is Lead Semi Wad Cutter (LSWC) 200 gr. all of Bullet Master, shot from a Colt Gold Cup 11 mm caliber at 7 different distances as 0.00, 0.15, 0.50, 1.00, 1.50, 2.00 and 2.50 meters to records a diameter of bullet hole. In this experiment, the shot at the close range could be seen most clearly physically. On the metal target, ring of the black gunshot residue around the collapse entrance of bullet holes and a tear at the exit of the bullet was appeared. The physical properties of bullet hole on the metal sheet of each bullet type are different that can basically inform about type of bullet (p < 0.05), at the 95% confidence level but the size of bullet hole can’t use for identity shooting distance.
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