Various casting methods (Plaster, Moulage, Faxfilm (Cowres, Davm L, Dodge, James K. A Method for Comparison of Tool Marks, 1948; Science and Practice Committee Report, 1949), plasticine (Kirk, 1953; O'hara & Osterbtrn, 1949), thermoplastics (Kirk, 1953), wax and electroplating (Tarko, 1948)) have been proposed for reproduction and comparison of individual characteristics marks on fired cartridge cases as an aid to firearms and tool mark identification. Most of the proposed methods had little or limited success due to time-consuming techniques and unsatisfactory results. In 1938, Moritz proposed a technique utilizing cellulose acetate with an acetone or amyl-acetate vehicle for the reproduction and comparison of the individual characteristics on cartridge cases, bullets and breech faces (Morrrz, 1938; Biasotti, 1956). The only advantage of the technique was preparation of flexible, translucent cast that could be flattened and viewed by transillumination thus reducing or obviating the difficulties inherent in the direct observation of curved or inaccessible surfaces by reflected illumination. Later, Faxfilm (trade name) became a commercial adaptation of the technique proposed by Moritz. It had larger application in studying the quality of finish on machined metal parts. The use of Faxfilm in law enforcement work has been reported, but literature on its practical application is meager (Science and Practice Committee Report, 1949; Biasotti, 1956). Cowles and Dodge have reported the successful application of Faxfilm to tool mark recovery and comparison and have pointed out its limitations when applied to deep impressions or to painted surfaces (Cowres, Davm L, Dodge, James K. A Method for Comparison of Tool Marks, 1948). Later another method for to form replicas of the fired bullets were proposed using sheets of vinyl thermoplastic varying in thickness from 0.030 to 0.125" (depending on the depth of the mark). The disadvantage of the method was the application of heat (100 to 125 °C.) and pressure (Kirk, 1953). An infrared lamp or electric hot plates were used for heating. These replicas were flattened and viewed by transillumination as either a positive or negative image. Accurate, reproducible replicas, free from air bubbles, shrinkage, and warping were obtained. However, the necessity of applying heat and pressure simultaneously, which may not be a serious disadvantage in the laboratory, makes this method rather impractical to use at the crime scene in the recovery of tool marks. Another material commonly used for lifting firing pin impression is plasticine, it is also used for replication of rifiling marks of fired bullet (Jain et al., 2004).
In the present study, plasticine and lead surfaces were used. The advantage of current method with previous methods reported is accurate, reproducible replicas, free from air bubbles and non application of heat and pressure for reproduction of marks. On comparison of firing pin and breech face impression of crime cartridge case with the impression of firing pin and breech face taken on plasticine. Three points in a match were found to be reproduced on the plasticine impression. Point-1 shows the periphery of the firing pin. Point-2 shows a horizontal line passing through the middle of firing pin impression. Point-3 shows a line at 7 O’Clock position (Fig. 4). However, the same impression was reproduced on lead surface was much pronounced than plasticine surface. Five match points were seen on the lead surface with clear demarcation (Fig. 5). Point-1 shows firing pin impression at 12 O’Clock position. Then moving down point-2 is a line at 2 O’Clock position. Point-3 shows an arc at 3 O’Clock position. In the middle a line crossing shows point-4. Point-5 is again a clear demarcation of firing pin impression at 6 O’Clock position.
