Waterways are popular locations for the disposition of criminal evidence because the recovery of latent fingerprints from such evidence is difficult. Currently, small particle reagent is a method often used to visualize latent fingerprints containing carcinogenic and hazardous compounds. This study proposes an eco-friendly, safranin-tinted Candida rugosa lipase (triacylglycerol ester hydrolysis EC 3.1.1.3) with functionalized carbon nanotubes (CRL-MWCNTS/GA/SAF) as an alternative reagent to the small particle reagent. The CRL-MWCNTS/GA/SAF reagent was compared with the small particle reagent to visualize groomed, full fingerprints deposited on stainless steel knives which were immersed in a natural outdoor pond for 30 days. The quality of visualized fingerprints using the new reagent was similar (modified-Centre for Applied Science and Technology grade: 4; p > 0.05) to small particle reagent, even after 15 days of immersion. Despite the slight decrease in quality of visualized fingerprints using the CRL-MWCNTS/GA/SAF on the last three immersion periods, the fingerprints remained forensically identifiable (modified-Centre for Applied Science and Technology grade: 3). The possible chemical interactions that enabled successful visualization is also discussed. Thus, this novel reagent may provide a relatively greener alternative for the visualization of latent fingerprints on immersed non-porous objects.

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Fingerprint has been one of the powerful evidence in forensic investigation as it is useful for human identification, associating an individual to an item and/or location of interest, as well as reconstructing the crime scenes. Considering that latent fingerprints are commonly found at crime scenes and that it requires the use of fingerprint visualization methods due to its hidden nature, continuous research in developing suitable methods has been reported. However, the underlying physical and/or chemical interactions for certain visualization methods that have successfully visualized wet fingerprints remains unreported. This is probably because previous studies were primarily focused on establishing the fingerprint contrast rather than the comprehension of the physical and chemical aspects behind it. A good understanding on such aspects may prove useful in guiding future improvements, or modifications of existing fingerprint visualization methods. Hence, this review paper focuses on wet latent fingerprints, difficulties in the available wet fingerprint visualization methods, as well as its overview of the challenges and future insights.

Considering the significant evidential values of fingerprints in underwater criminal investigations and the need to visualise them using a user-and environmentally-friendly reagent, development of a novel, rapid and relatively greener nanobio-based reagent (NBR) is deemed beneficial. Lipase from the commercial Candida rugosa immobilised onto acid-functionalised multi-walled carbon nanotubes (NBR) was used as the safer and cheap lipid-sensing reagent to visualise groomed whole/split fingerprints on non-porous objects immersed in stagnant tap water for up to days under a laboratory-controlled setting. Attenuated Total Reflectance-Fourier Transform Spectrometry, Field Emission Scanning Electron Microscopy and bioinformatics (molecular docking and molecular dynamics simulations) were employed to characterise and confirm the attachment of NBR onto the lipid constituents of wet fingerprints. Chromatographic results further confirmed the presence of n-hexadecanoic and octadecanoic acids on fingerprints up to days of immersion. Thus, NBR may potentially be useful as the future state-of-the-art fingerprint visualisation technology. ©

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