In order to improve the development effect of latent blood fingerprint, this paper attempts to introduce fuorescent labeling technology into latent blood fngerprint development. By taking advantage of the characteristics of strong esterification activity of N-hydroxy-succinimide ester, easy reaction with the amino group of protein to form amide chemical bond and stable structure, a new fluorescence derivative 5-carboxyfluorescein-N-hydroxy-succinimide ester (CFSE) was synthesized and applied to latent blood fngerprint development area for the frst time. In this paper, the developing ability of CFSE on latent blood fingerprint will be systematically explored. By setting a series of gradients, using comparative experiments, hypothesis testing and other methods, the operation method and optimal reagent formula of the fuorescein to develop latent blood fngerprints were determined. CFSE can be widely used in the development of latent blood fngerprints on non-permeable complex backgrounds and dark background objects, and has little effect on sample DNA extraction, and compared with acid yellow, the results showed that the fneness of the lines and the contrast with the background were higher. In addition, the study also determined the order of using CFSE in combination with the common methods for developing latent blood fngerprints. CFSE has the advantages of strong fuorescence brightness, high fneness, obvious contrast with the background, less fuorescence stains, and easy washing, and the overall effect is better, which provides a new method for latent blood fngerprints development.

In order to study the feasibility of using fluorescein to develop latent blood fingerprints based on fluorescent labeling technology and explore the optimal conditions for its development, we selected two cselected used fluoresceins (FITC fluorescein and DCFH-DA fluorescein) as the main research objects of this experiment, to design the method and procedure of developing latent blood fingerprints on non-porous surfaces with fluorescein, based on the principle of fluorescent labeling technology. On this basis, PBS buffer was used to change the pH environment of fluorescein solution, and acetone was used to dilute the two fluorescein solutions by 5 times, 10 times and 100 times, respectively, in order to explore the best developing conditions of latent blood fingerprints. The results showed that both FITC fluorescein and DCFH-DA fluorescein were effective in developing latent blood fingerprints on non-porous surfaces. The best conditions for FITC fluorescein to develop latent blood fingerprints on non-porous surfaces are: the developing time being 10 minutes, the pH environment value being 9.35, and the concentration being the original concentration; The best conditions for DCFH-DA fluorescein to develop latent blood fingerprints on non-porous surfaces are: the developing time being 20 minutes, a pH environment value being 13.01, and the concentration being the original concentration. Therefore, it is feasible for the fluorescence labeling technology to develop latent blood fingerprints on non-porous surface, but it is still necessary to further explore the preservation time of prepared fluorescein solution and the damage of DNA detection in blood fingerprints by this technology, and comprehensively analyze its practical application value.