Small Particle Reagent Technique of Fingerprint Development

SPR can be used for wet and non-porous surfaces and it gives very effective results. It has certain advantages and some limitations too.

1. Small Particle Reagent (SPR)

2. Rituja R. Gharote Masters of Science in Forensic Science Sem III, Fingerprints Unit 1: Powder Methods Submitted to: Miss Hansi Bansal Ma'am

3. Sr. No. CONTENTS 1 Introduction of Small Particle Reagent (SPR) 2 Surfaces on which SPR can be used 3 Development of prints using SPR 4 Lifting and Photographing the prints developed by SPR 5 Types of SPR 6 Advantages and Disadvantages of SPR 7 Comparison of SPR with other Techniques 8 References

4. 1.1) Small Particle Reagent: The method is based on the adherence of fine particles of treating solution to the oily or fatty components of latent fingermark residues. It interacts with the water insoluble sebaceous components of latent fingermark residues. Conventionally, SPR consists of a suspension of fine molybdenum disulfide particles in an aqueous medium containing detergent solution (as surfactant). These particles adhere to fatty components of latent fingermark residues and form a gray deposit. This method is also considered as wet powdering method.

5. 1.2 ) The reagent used for development of prints using SPR: Surfactant and suspension material are the main components of conventional SPR composition. Surfactant is a surface active agent and a synthetic detergent . It reduces the surface tension of water , enhances the moisture on surface and uniformly distributes the suspension material of moist surface. Suspension material adheres to fatty components of residue and provides color to them. The use of tergitol-7 detergent in combination with choline chloride in molybdenum disulfide is preffered.

6. 1.3) Preparation of working solution: In order to prepare SPR composition, dissolve the suspension material in distilled water and add 3 drops of surfactant to it and shake the solution well to ensure that suspe n sion material has gone into solution. Pre-treatment of surface with volatile bases such as ethanolamine or triethylamine was recommended before development of latent fingermarks on acidified non-porous substrates with SPR. Post-Treatment : The wiping of SPR treated non-porous substrates with paper towel was recommended in order to improve the effectiveness of SPR process in significant manner.

7. 2) Surfaces on which SPR can be used: 1. SPR is useful on wet surfaces (where drying is not possible). 2. Also on surfaces covered with a residue, like salt (close to sea shores) or dirt /grease. 3. It can also be applied on waxed materials, plastics like polyethylene bags as well as polystyrene (packaging material). 4. It is also preferable for development of prints on the sticky side of tape. 5. It can also be used on wood, metal, glass and vinyl surfaces.

8. 3) Process of Development using SPR: Spray Application: In th is spray process , the area where fingerprints are suspected is sprayed with working solution, using a spray unit . The nozzle of the spray unit is adjusted to g ive a cone-shaped jet . Shake the spray unit before and between sprays. The powder in the suspension will settle in a few minutes. Therefore, the solution has to be agitated frequently to keep the powder in susp ension,

9. 2. Dish development Th is method uses a container / dish with working solution in which the article, on which fingerprints are suspected, is submerged. The working solution for dish development is less concentrated than the working solution for spray application. S ubmerging the article after the solution is thoroughly stirred and le ave in the solution for 30 seconds and then removed. Do not agitate the solution while in the container. Many articles will have to be immersed twice, once for each side.

10. 4) Lifting and P hotographing : Before lifting, the prints should be allowed to dry. The molybdene disulfide powder from black SPR moves easily, so if the air stream is too powerful false ridges can be created. The ease with which the powder flows, makes it necessary to be extra careful in lifting. Prints are easily damaged. P hotographing before lifting is recommended in important cases or if lifting is done from difficult surfaces. Prints can be lifted, once dry, with black Gellifters.

11. (1) SPR White SPR Black SPR UV (2) (3) 5) Types Of Small Particle Reagent:

12. 1 ) SPR White: SPR White is a suspension of white powder in water with a detergent. It contains titanium dioxide. It provides better contrast on dark surfaces like black electric tapes both adhesive and non-adhesive sides. Background staining is more pronounced with white SPR. Rinsing with water after appl ying white SPR works best.

13. Close up of a print developed by SPR white. Image Source: https://www.bvda.com/en/small-particle-reagent

14. 2) SPR Black: SPR Black is a suspension of molybdenedisulfide powder in water with a detergent. U se of xerox powder, lead oxide, cobalt oxide and graphite in place of molybdenum disulfide particles as an alternative . The powder particles adhere to a fingerprint as does a fingerprint powder. The gray, shiny prints that are developed with SPR can be lifted (after drying) with Gel - lifters, Instant Lifters or tape. The SPR method has the advantage that it can be used on wet and/or dirty/greasy surfaces.

15. SPR black developed prints on White Surface Image Source: https://www.bvda.com/en/small-particle-reagent

16. 3) SPR UV: S PR UV is a suspension of light coloured UV fluorescent pigment in water with a detergent. It is used in the same way as the black and white version . A light source emitting long wave UV light (365 nm) is needed to view the developed marks in fluorescence. SPR UV may provide better contrasting marks on multi coloured surfaces.

17. SPR Uv developed prints on blue Metal Surface Image Source: https://www.bvda.com/en/small-particle-reagent

18. 6.1) Advantages of SPR: 1) SPR technique is a convenient, cost-effective and efficient method to develop latent fingermarks on wide range of wet, non-porous surfaces. 2)The present technique is simple and even an amateurish hand can operate it without any requirement of specialized equipment. 3) Contents of SPR doesn't affect the wet surfaces (e.g, bloodied surfaces). The samples are found non-contaminated while performing STR Typing for DNA Profiling.

19. 1) SPR cannot be used on porous surfaces like paper or cardboard. 2) SPR is very messy and can be difficult to remove from porous surfaces, care should be taken to avoid property damage. 3) Concentration of reagents should be optimized as higher concentration of surfactant develops weaker prints. 4) Fresh fingermarks responded better than aged fingermarks to SPR processing. 5) The working solution is for one time use, one cannot store it. 6) It is highly sensitive amd harmful to an user and environment. 6.2) Disadvantages of SPR:

20. 7) Comparison of SPR with Other Techniques: 1) P owder suspensions will develop more clear prints than SPR . 2) SPR is more effective than cyanoacrylate fuming on water soaked firearms but results are converse in case of dry surfaces. 3)White SPR method is more effective than Swedish soot mixture powder for developing aged latent prints on wet surfaces. 4) CA fuming method is more effective than SPR in developing aged (upto 168 h) latent fingerprints on glass and metal surfaces immersed in stagnant water. 5) SPR is preffered over Vaccum-Metal Deposition.

21. 8) RE FERENCES:- 1) BVDA - Small particle reagent. Bvda.com. (2020). Retrieved 8 December 2020, from https://www.bvda.com/en/small-particle-reagent. 2) Bvda.com. (2020). Retrieved 8 December 2020, from https://www.bvda.com/images/content/downloads/SPR_instructions_for_use_EN.pdf. 3) Sodhi, G., & Kaur, J. (2012). A novel fluorescent small particle reagent for detecting latent fingerprints on wet non-porous items. Egyptian Journal Of Forensic Science, 2, 45-47. Retrieved 8 December 2020, from https://www.researchgate.net/publication/257737214_A_novel_fluorescent_small_particle_reagent_for_detecting_latent_fingerprints_on_wet_non-porous_items.

22. 4) Jasuja, O., Toofany, M., Singh, G., & Sodhi, G. (2009). Dynamics of latent fingerprints: The effect of physical factors on quality of ninhydrin developed prints — A preliminary study. Science And Justice, 8-11. Retrieved 8 December 2020, from https://www.researchgate.net/publication/23421613_Small_particle_reagents_Development_of_fluorescent_variants. 5) Ncids.com. (2020). Retrieved 8 December 2020, from http://www.ncids.com/forensic/labs/Latent/Technical/SPR.pdf.

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