Milutin Stoilovic

Synthesis of Ninhydrin Analogues and Their Application to Fingerprint Development: Preliminary Results

Abstract The synthesis of ninhydrin analogues and their application to the development of latent fingerprints on paper surfaces has been investigated. The substituted ninhydrins developed latent fingerprints with a sensitivity similar to that of ninhydrin itself (with print colours ranging from pink to dark green to black). Photoluminescent complexes were formed by secondary metal salt treatment and spectral data are reported. Preliminary results indicate that some of the analogues may be useful on surfaces where background luminescence precludes successful enhancement of ninhydrin-developed prints.

Improved enhancement of ninhydrin developed fingerprints by cadmium complexation using low temperature photoluminescence techniques.

Fingerprints developed with ninhydrin form stable, colored complexes when treated with various metal salts. Many of these colored complexes can be used to increase the sensitivity of detection of latent prints because of photoluminescent properties. The intensity of this photoluminescence is increased at low temperature (77K), and this is a common characteristic of each of the complexes formed with salts of the IIb group of the Periodic Table. Spectral characteristics of these Group IIb metal complexes and the influence of environmental factors on their formation are reported. These data have helped determine optimal conditions for the enhancement of ninhydrin developed fingerprints. Taking into account spectral characteristics, solubility, versatility, stability, and reproducibility, the use of the cadmium nitrate tetrahydrate complex is advocated for general use for fingerprint enhancement. The use of zinc nitrate is favored if toxicological considerations are paramount, but ninhydrin development has to be carefully controlled if optimal results are to be obtained. Limited applications for mercuric complexes are found when a red shift is desired to remove background effects.

A SIMPLE LUMINESCENT POST-NINHYDRIN TREATMENT FOR THE IMPROVED VISUALISATION OF FINGERPRINTS ON DOCUMENTS IN CASES WHERE NINHYDRIN ALONE GIVES POOR RESULTS

Abstract Increased fingerprint ridge detail can be produced from ninhydrin prints on documents using a secondary chemical treatment. This involves conversion of the ninhydrin print into a luminescent metal complex by treatment with zinc chloride where even weak ninhydrin prints yield ridge detail which can be readily photographed. Several technical advances are offered in the present report which make it attractive to a range of fingerprint departments: (1) the treatment need not be carried out until normal ninhydrin (NFN) evaluation has been made; (2) the method does not require especially expensive equipment; (3) the luminescence is produced using a xenon arc lamp following cooling of the document print to liquid nitrogen temperatures; (4) a laser light source is not required; (5) prints can be recorded using normal photographic equipment; and (6) the method has been applied to casework studies.

Synthesis and evaluation of ninhydrin analogues as reagents for the development of latent fingerprints on paper surfaces

Abstract Thirteen ninhydrin analogues have been synthesized and evaluated as amino acid-specific fingerprint reagents. All of the ninhydrin analogues tested developed latent fingerprints on paper surfaces in a manner similar to ninhydrin itself. The photoluminescent enhancement of prints developed with each reagent was assessed after treatment with zinc(II) or cadmium(II). The results obtained have been related to the effects of substitution on the ninhydrin skeleton. Two compounds in particular, 5-methoxyninhydrin and benzo[f]ninhydrin, were shown to offer operational advantages over ninhydrin on a number of difficult surfaces. Prints developed with either reagent show stronger room temperature luminescence after zinc(II) or cadmium(II) treatment in comparison with equivalent prints developed with ninhydrin. Both 5-methoxyninhydrin and benzo[f]ninhydrin have been shown to be effective on surfaces where background luminescence precludes the successful enhancement of ninhydrin-developed prints.

Two simple staining procedures which improve the contrast and ridge detail of fingerprints developed with “Super Glue” (cyanoacrylate ester)

Abstract The use of cyanoacrylate ester vapour (Super Glue) has become a popular technique for the development of latent fingerprints. This paper describes two staining procedures for improving the contrast of weak Super Glue fingerprints based on the selective absorption of the stain by the polymerised Super Glue. One procedure uses Gentian Violet and is particularly suited to clear polythene. The other is a fluorescent method using a laser dye Coumarin 540 and is particularly suited to reflective surfaces such as aluminium foil and chrome.

An evaluation of the reagent NBD chloride for the production of luminescent fingerprints on paper: I. Support for a xenon arc lamp being a cheaper and valuable alternative to an argon ion laser as an excitation source

Abstract Strongly luminescent fingerprints can be produced on paper by initial treatment of the latent print with the chemical reagent NDB chloride (4-chloro-7-nitrobenzofurazan), followed by excitation with a 150-W xenon arc lamp filtered to transmit light in the 475-nm spectral region. The fingerprint quality and ridge detail obtained using the xenon arc lamp was equal to that obtained using a 3-W argon ion laser. The marked cost and operational advantages of the xenon arc lamp clearly offsets the small increased photographic exposure time (about 6-fold) needed to obtain photographic records with this light source compared with the laser. Each source produces fluorescent images suitable for visual examination of test objects, with the xenon lamp requiring less stringent eye protection facilities than the laser. Some of the limitations of this reagent are discussed.

An evaluation of the reagent NBD chloride for the production of luminescent fingerprints on paper: II. A comparison with ninhydrin

Abstract The effectiveness of the fluorogenic reagent NBD chloride has been compared with the popular colour reagent ninhydrin for the development of fingerprints on paper. NBD chloride was found to be more sensitive than ninhydrin for moderately old fingerprints (3–9 months) and never inferior to ninhydrin in all other cases. A qualitative evaluation technique was used to establish the relative efficiency of each method. This is based on the number of points of identification, assessed on a 1–4 scale, where 4 represents a courtworthy print (> 12 points) and 1 represents a print containing no identification points.