There are many different fingermark visualization techniques available, and the choice of methodology employed may be dependent on the surface type. This comprehensive review of the scientific literature evaluates the methodologies of fingermark enhancement methods that are applicable to metallic surfaces; optical, physical, chemical, and physicochemical methods are critically discussed. Methods that are currently used and those that have the potential to reduce the cost and time required to process evidence and increase the recovery rates are considered and are assessed against the Centre for Applied Science and Technology (CAST) and the International Fingerprint Research Group (IFRG) guidelines. The use of chemical imaging techniques in particular has increased the potential to recover fingermarks of sufficient quality for identification purposes. Presently, there appears to be a lack of detailed research pertaining to validation and thorough casework studies for fingermark enhancement techniques. Further studies incorporating these guidelines are recommended.KEYWORDS: forensic science, fingermarks, fingerprints, enhancement techniques, metallic surfaces, latent fingermarks Fingermarks are considered one of the most valuable types of physical evidence recovered from a crime scene. Fingermark casework is still the most common casework for forensic scientists despite the increase in use of DNA (1) to identify/exonerate suspects via bodily fluids (2). The ridge patterns found in fingermarks are permanent and can be used to individualize or exclude suspects from an investigation.Detection of fingermarks on metallic surfaces will be dependent upon the compounds remaining from the fingermark residue. Several detailed reviews have already been published on fingermark composition, but none have focused on fingermarks deposited on metallic surfaces (3,4).Generally, there are two types of fingermarks found at crime scenes: visible fingermarks, usually formed by fingers contaminated by a substance such as oil, fruit, grease, paint or blood, which are deposited on a surface; and latent fingermarks, which are invisible to the naked eye and are the most abundant type of fingermarks at crime scenes. Metallic surfaces are also commonly encountered in crime scenes and are ubiquitous in the environment. Surfaces such as the door of a car, objects like handles, weapons, and tools are usually made of steel. Cartridge cases are frequently recovered from crime scenes and are usually made of brass or nickel (5). There are a number of different techniques that can be applied to a surface to visualize latent fingermarks. The selection of a suitable technique depends on different factors, such as the expected composition of a fingermark, the ability of the chosen technique to be used in tandem with other techniques, and the nature of the substrate. In this review, the focus will be on fingermarks deposited on metallic surfaces, and the optical, physical, chemical, and physicochemical visualization techniques that can be used ...

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In order to assess the efficacy of vacuum metal deposition (VMD) as a technique to develop fingermarks on ballistic metallic surfaces, a preliminary study using six donors (three male & three female) was conducted. Using a sequential metal deposition process, two metal combinations were studied—gold/zinc and silver/zinc. Results indicate the potential of this technique, by developing identifiable fingermarks on brass metal disks aged from a few days up to more than a month old. As the development of fingermarks on fired (brass) cartridge cases is an area of interest, a further study was conducted where a total of 20 fingermarks were deposited on cases. After firing, second level fingermark characteristics were successfully observed on cartridge cases highlighting its potential as a fingermark enhancement method for ballistic brass materials. Further work is required to fully evaluate the VMD process and its reliability as a fingermark enhancing method on ballistic surfaces.

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