Latent Fingerprint detection

 When fingertips touch any surface they deposit minute quantities of chemicals exuded through the pores as a solution in sweat. Typical components deposited on contact include a range of organic molecules: peptides, lactic acid, branched chain hydrocarbons,  glucose, riboflavin and traces of DNA. Some of these molecules can act as nucleation sites for the common technique of super-glue (cyano-acrylate) fuming that results in a white deposit to outline the previously invisible fingerprint.

fingerprint image

 This technique is only effective on a limited range of substrates, soft materials such as fabrics, human skin and paper pose a major challenge to the forensic investigator attempting to retrieve latent fingerprints.

We are collaborating with a team led by Prof. Claude Roux from the University of Technology Sydney on novel methods based on delayed luminescence imaging for the detection of latent fingerprints. Our proposal is to use a 'smart' phone with a high resolution imaging capability (8 megapixel) and fit it with a modified GALD device. The image shown below was taken of a latent fingerprint produced by coating a finger with a very dilute solution of a luminescent europium compound. The fingerprint image was captured on a HTC smartphone to prove the feasibility of using the phone as a low cost handheld fingerprint capturing tool.

latentfingerprint detection 

 The image on the left shows a latent fingerprint on white paper that fluoresces intensely when illuminated with a strong UV source from the GALD. When this same area is viewed through the GALD the latent fingerprint can be clearly seen - the native autofluorescence of the paper is completely supppressed.

This was a proof-of-concept test, we now need to identify a technique to selectively bind the europium dye to the chemical components within latent fingerprints - this is an ongoing research project !

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