Fingerprints Development with Cyanoacrylate Followed by Fluorescent Enhancement Technology--Taking Synthetic Leather for Example

• Main Authors: Wu,I -Nong, 吳宜濃
• Other Authors: Pai,Chung-Yen
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/pwuv4b

碩士 === 中央警察大學 === 刑事警察研究所 === 107 === The leather products (for example, wallets and handbags) are one of the most frequent theft cases encountered in Taiwan. The fingerprints from the thief can be used to investigate the burglar’s identity; however, the evelopment of latent fingerprints left on the item surface often failed in practice. We aimed to enhance the readability of fingerprints on such physical evidences by using the cyanoacrylate fuming method and then fluorescent reagents development coupled with alternate light source. The experimental design was divided into three stages. The first one compares the appearance degree of fingerprints on synthetic leather items by three fluorescent methods (BY40, MBD, and fluorescent powder). All the synthetic leather samples were first developed with cyanoacrylate fuming, and the treated with the reagents of BY40, MBD as well as fluorescent powder. The results were recorded by cut into half-and-half comparison. The best reagent from stage one was then compared with rhodamine 6G fluorescent reagent, frequently used in practice. The result was also recorded using the same half-and-half comparison strategy. The third stage focused on the multiple factors on appearance effectiveness, for examples, different ages and genders, the influence of deposited days of the fingerprint samples, decay of developed fingerprints, and different manufactured leather surface (deep, light, smooth and matte). The commercially available synthetic leather (PU material) samples were focused in this study. The result of stage one showed that BY40 (using 420nm light coupled with yellow filter) was the best, MBD (using 365nm light coupled with orange filter) was the second, and the fluorescent powder was the worst. In stage two, the BY40 (using 420nm, 445nm, and 470nm light coupled with yellow filter) was still better than rhodamine 6G (using 495nm, 515nm, and 530nm light coupled with orange filter). As for the stage three, the experimental results showed that fingerprints of different ages and genders have no obvious difference in the appearance of synthetic leather; while the longer the days of fingerprint placement on the leather surface, the worse the sharpness of the fingerprint ridge. Fluorescent fingerprint stability can last for at least one month. In addition, the fingerprint ridge clarity on the smooth leather is clearly better than the matte surface. Our results would be beneficial for the development of latent fingerprints on the leather surface items in practice.