Relevant visualization technologies for latent fingerprints on wet objects and its challenges: a review <s> General powder suspensions <s> Physical developer (PD) is a fingermark development technique that deposits silver onto fingermark ridges. It is the only technique currently in routine operational use that gives results on porous substrates that have been wet. There is a reasonable understanding of the working solution chemistry, but the chemical constituent(s) contained in fingermark residue that are specifically targeted by PD are largely unknown. A better understanding of the PD technique will permit a more informed selection of alternative or complementary detection methods, and greater usage in operational laboratories. Recent research by our group has shown that PD does not selectively target the lipids present in the residue. This research investigated the hypothesis that PD targets the eccrine constituents in fingermark residue. This was tested by comparison of PD and indanedione-zinc (Ind-Zn) treated natural fingermarks that had been deposited successively, and marks that had been deposited with a ten second interval in between depositions. Such an interval allows for the regeneration of secretions from the pores located on the ridges of the fingers. On fingermark depletions with no time interval between depositions, PD and Ind-Zn treated depletions successively (and comparatively) decreased in development intensity as the amount of residue diminished. Short time intervals in between successive depletions resulted in additional secretions from the pores intermittently occurring, the increased development of which was visualised by treatment with both PD and Ind-Zn. The changes in development intensity were seen with both techniques on the same split depletions in a series, comparably and proportionately. These results indicate that the components targeted by PD are contained in the material excreted by the friction ridge pores through its mirrored development with Ind-Zn. Repetition of the experiments on marks that only contained eccrine material showed good Ind-Zn development but poor results with PD. This indicates that there are other constituents contained in "natural" fingermarks that are required to be present for PD to be able to target constituents in the eccrine sweat. It may be that the required constituents in the natural residues are non-water soluble, and that these protect the eccrine constituents from solubilisation in the aqueous washes employed in the PD method. Further research is being undertaken to determine whether PD is targeting specific compounds in the pore secretions, or a mixture of compounds consisting of the eccrine material, epidermal lipids and sebaceous lipids typically present in latent fingermark residues. <s> BIB001 </s> Relevant visualization technologies for latent fingerprints on wet objects and its challenges: a review <s> General powder suspensions <s> Friction ridge examination is one of the bedrock disciplines in forensic science and has been employed for over 100 years. It is considered the pre-eminent method of individualization in forensic science. That status, however, has recently been upset by court challenges and high-profile misidentifications. Friction ridge examination will no doubt continue as a mainstay of forensic science, but changes in methodology and interpretation may be on the horizon. How the discipline weathers these changes depends on the willingness of the profession to critically examine their foundations, procedures, and methods. <s> BIB002 </s> Relevant visualization technologies for latent fingerprints on wet objects and its challenges: a review <s> General powder suspensions <s> Fingerprints have been used for human identification in criminal investigation for over 100 years. The detection of invisible or latent marks at crime scenes has been one of the great scientific challenges in forensic science and there have been considerable advances in this capability. The technological age and increasing power of computing has had a major influence on fingerprint identification providing the capacity to search large databases and provide rapid identification of persons of interest. This chapter discusses the important contribution of fingerprints to criminal investigation. <s> BIB003
Historically, the development of conventional black powder suspensions (which later commercialized as Sticky-side Powder™) for developing fingerprints on the sticky side of tape was first introduced by  . Beneficially, powder suspension techniques work best on sticky-side of the adhesive tapes where common powder methods are futile. As the name implies, this technique is based on suspended powder particles (carbon-, titanium dioxide-, or iron-based) in a mixture of water and diluted detergent (e.g., Kodak Photo-Flo™ or Liquinox™), which is basically similar to that of SPR except for its thicker (paint-like) consistency   ). This technique has been reported suitable for enhancing fingerprints on wet non-and semi-porous surfaces    ) via spraying, painting, and dipping BIB001 . Because the traditional black powder suspension produced poor background contrast on dark surfaces,  investigated the potential combination of Kodak Photo-Flo with white SPR (titanium dioxide-based powder) where better quality of visualized fingerprints on both sides of black tape was observed than the use of white SPR alone. Similar efficiency of such reagent was also further supported by  . It has been speculated that the successful visualization of fingerprints using this technique is associated with its interactions with that of the water-soluble constituents encapsulated within the non-water soluble constituents  . Unlike any other powder-based method, wet powder suspension techniques have been reported to work best on aged latent fingerprints  .  reported that the concentration of the surfactant in the iron-based reagent plays a major role in determining the clarity of the quality of visualized fingerprints, probably because surfactant helps to control the preferential deposition of suspended powder particles onto the constituents of fingerprints by forming stable micelles  . For multi-colored surfaces, fluorescent powder suspensions (e.g., rhodamine 6G and basic yellow 40) were introduced. Despite its usefulness in visualizing wet latent fingerprints, the mechanism behind the successful visualization remains a subject of debate. Chemical visualization methods: iodine fuming, physical developer, multi and single metal depositions, as well as Oil Red O Since the choice of chemical methods relies largely on the available constituents of fingerprints as well as the sequence of application  BIB001 BIB002 BIB003 , careful selection of such methods must be made, as one method might preclude the other or reveal more fingerprints than one process alone BIB003 .