Fingerprint Collection Methods
Describe the different methods used to collect fingerprint evidence from hard/non-absorbent surfaces and soft/porous surfaces
Fingerprint collection is a sensitive forensic process that is determined by a broad range of factors, including visibility (patent vs. latent) and surface (rough, porous, and nonporous) (Abebe, Murthy, Amare, & Dessie, 2020). The present piece offers a brief explanation of key techniques used to obtain fingerprint evidence from non-absorbent and porous surfaces. It should be clarified that the key techniques include high-resolution photography for patent fingerprints on non-absorbent surfaces and chemical developers for porous surfaces.
Non-absorbent surfaces are typically hard and compact. Common examples of this type of surface include materials such as glass, metal, and plastic. These surfaces often have visible (patent) prints due to their hardness. In such cases, forensic specialists use straightforward methods such as photography to develop high-resolution images of the print. Alternate light sources, mainly LED and laser devices can be used to enhance visibility and image quality (Hytinen, Solomon, Miller, & Cruz, 2017). When fingerprints on such surfaces are not desirably visible, the investigator can utilize the dusting technique by applying powders such as aluminum flake, black granular, or black magnetic print powder to enhance clarity. In this case, a clear adhesive tape is used to transfer the powdered print to a latent lift card for the sake of preservation.
When dealing with porous surfaces, investigators rarely find patent prints, unless the finger/surface was in contact with adhesive elements such as blood, paint, or wax among others. Since most of these prints are latent, the most appropriate technique is chemical developer reaction. Forensic specialists use chemicals such as ninhydrin to foster reaction with invisible residue from the latent print (Abebe, Murthy, Amare, & Dessie, 2020). For instance, ninhydrin turns the components to purple, thus enhancing visibility for photography. Another common chemical is 2-diazafluoren-9-one, which glows upon reaction to fingerprint residues (Abebe, Murthy, Amare, & Dessie, 2020). Noteworthy is the fact that this glow is visible under blue-green bulbs.
In conclusion, fingerprint collection is an interesting process through which prints are obtained from surfaces regardless of their visibility and/or the materials on which they reside. Straightforward photography is common in non-absorbent materials while chemical developers are often applied to porous surfaces.
Abebe, B., Murthy, H. C. A., Amare Zereffa, E., & Dessie, Y. (2020). Latent Fingerprint Enhancement Techniques: A Review. Journal of Chemical Reviews, 2(1), 40-56.
Hytinen, M. E., Solomon, A. D., Miller, M. T., & Cruz, T. D. (2017). Methods for Obtaining High-Quality Touch DNA from a Nonporous Surface after Latent Fingerprint Collection. Journal of Forensic Identification, 67(1).