Several new methods for the development of latent and blood fingerprints
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Several new methods for the development of latent and blood fingerprints have been investigated as well as a preliminary appraisal of a technique for the estimation of post-mortem interval and age of blood stains. The utilisation of coordinatively-unsaturated (six-coordinate) europium and terbium complexes as reactive reagents for the direct visualisation of latent fingerprints on porous and non-porous surfaces has been investigated. The main complex investigated in this study was tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III) [Eu(fod)₃] and was the only one which proved to be effective in the fluorescent visualisation of latent fingerprints using a one step process. Eu(fod)₃ was found to work for fingerprints on porous paper and to a limited extent on aluminium drink cans and galvanized iron. The use of the two and three ringed analogues of ortho-phthalaldehyde (OPA) for the fluorescent enhancement of latent fingerprints was also investigated. Solution trials proved that the reaction products of 2,3-naphthalenedicarboxaldehyde (NDA) and 2,3- anthracenedicarboxaldehyde (ADA) with analine produce favourable “red-shifts” in emission wavelengths which would make them stand out from the blue background emissions commonly obtained from paper. However, poor results were obtained when NDA and ADA were trailed on latent fingerprints on paper. 2,2’-azino-di-[3-ethylbenzthiazolinesulfonate(6)] diammonium salt (ABTS), ortho-phenylenediamime (OPD), and para-phenylenediamine (PPD) have been found to be successful reagents in the visual enhancement of blood fingerprints. Colours obtained from the oxidised products are green, orange, and purple respectively. A comparison with the commonly-used and hazardous 3,3’-diaminobenzidine (DAB) has proved all three reagents to be effective, safer alternatives with the added bonus of ABTS being (as far as is known) non-toxic. A preliminary appraisal has indicated that fluorescein diacetate (FDA) may be useful in estimating the post-mortem interval or age of blood stains and blood prints. Of the range of techniques and processes investigated with the aim of improving fingerprint visualisation, some proved unsuccessful, yet provided some useful information. These included attempts to improve the colloidal gold technique of latent fingerprint visualisation, increase the chemiluminescence from luminol-treated blood fingerprints in the presence of bromide ions, increase the colour development of ABTS-treated blood fingerprints using an albumin antibody conjugated to peroxidase, an attempt to force fluorescein into the lipid component of a latent fingerprint by acidification of an alkaline solution of fluorescein, and an attempt to stain blood fingerprints with a fluorescent protein stain called SYPROᵀᴹ Orange.
The University of Waikato
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