Evaluation of 1,2-indanedione and 5,6-dimethoxy-1,2-indanedione for the detection of latent fingerprints on porous surfaces

The ability of 1,2-indanedione and 5,6-dimethoxy-1,2-indanedione to detect latent prints on porous surfaces, as compared to DFO and ninhydrin, has been evaluated. Comparisons of prints developed under various conditions determined the optimum development conditions for the new reagents. The indanediones tested were found to have lower detection limits for glycine. The carrier solvent used was found to affect the quality of the prints developed. In Arklone, the new reagents developed prints that displayed superior luminescence to those developed with DFO. In HFE 7100, 1,2-indanedione and 5,6-dimethoxy-1,2-indanedione gave superior luminescence to DFO after zinc salt treatment and cooling with liquid nitrogen, both of which improve the luminescence of prints developed with 1,2-indanediones. 1,2-Indanediones could offer less expensive but effective alternatives to DFO. With further optimization, the new reagents may supersede DFO as the method of choice for the detection of latent fingerprints on porous surfaces.     

Detection of semen and blood stains using polilight as a light source.

Photoluminescence spectra of dry untreated semen have been measured and a suggested method for rapid detection of untreated semen stains is derived from these measurements. The method is presented in the form of a flow chart to cover most crime scene situations. The absorption spectrum of dry untreated blood has also been measured and a suggested method for enhancement and photography of blood stains is derived from this measurement. The method is presented in the form of a flow chart. Both methods are based on the use of a high intensity light source such as the Polilight.     

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

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.     

Vacuum metal deposition: visualisation of gold agglomerates using TEM imaging

Vacuum metal deposition (VMD) is a well-established technique that can be used for the development of latent fingermarks on a range of polymer surfaces, including polyethylene (PE) bags exposed to harsh environmental conditions. The technique has also proved to be effective on difficult semi-porous surfaces such as the polymer banknotes in circulation in Australia and in an increasing number of other countries. VMD is a two-stage technique. In the first stage, a small amount of gold is deposited under high vacuum onto the exhibit. This is then followed by the deposition, onto the gold layer, of a much thicker layer of zinc. Normal VMD development is characterised by zinc depositing all over the surface except on the fingermark ridges themselves. A phenomenon of reverse development (zinc on the ridges but not on the surface) has been reported by many authors. Recent studies indicated that this phenomenon might occur on low-density polyethylene (LDPE) when the amount of deposited gold is above an optimum quantity. The results suggested that the size of the gold agglomerates formed on the surface of the polymer plays a critical role. This preliminary study was aimed at visualising, by transmission electron microscopy (TEM), the formation of gold agglomerates on polymer surfaces to gain an appreciation of how the density and size of these agglomerates changes with an increasing amount of evaporated gold.     

Optimisation and evaluation of 1,2-indanedione for use as a fingermark reagent and its application to real samples

1,2-indanedione is an emerging fingermark reagent used on porous surfaces. The general consensus is that this reagent is at least as sensitive as DFO, with some research showing higher sensitivity for 1,2-indanedione as opposed to DFO. However, a number of discrepancies existed in the literature as to which formulation and which development procedure produces optimal results. This project set out to investigate the best formulation and development procedure under Australian conditions, encompassing all published recommendations as well as some novel approaches. 1,2-indanedione formulations were compared with respect to initial colour, fluorescence, concentration of reagent, acetic acid concentration, and the effect of different carrier solvents. Numerous development conditions were investigated, including a conventional oven, a heat press and humidity. Further enhancement using metal salt treatment and liquid nitrogen was also evaluated. The heat press set at 165 degrees C for 10s proved to give the best initial colour and most intense luminescence. Secondary metal salt treatment improved initial colour and luminescence. The Polilight, the VSC 2000, and the Condor Chemical Imaging macroscope have been used to detect the fingerprints developed with 1,2-indanedione on a variety of high- and low-quality porous and semi-porous surfaces, with impressive results overall. Laboratory and field tests were conducted to compare 1,2-indanedione with DFO and ninhydrin as well as to investigate the position of 1,2-indanedione in the sequence of reagents for fingermark detection on porous surfaces. Overall, 1,2-indanedione proved to be a viable alternative to traditional methods for the detection of fingermarks on porous surfaces, with more fingermarks being developed using this reagent on real samples than both DFO and ninhydrin and a combination of the two reagents.     

Improved method for DFO development of latent fingerprints

A new formulation has been developed for DFO stock solution. The working DFO solution, based on the new stock solution, appears to be more stable, has a longer shelf life, and has little effect on inks (and therefore does not cause inks to run). Photoluminescence spectra of latent fingerprints developed with DFO reagent have been measured and the choice of filters for excitation and emission (barrier) have been derived from these measurements. Comparisons of latent fingerprints developed with ninhydrin and DFO have been made using various papers and at various intensities. These comparisons show the much greater sensitivity of DFO developed latent fingerprints. Although enhanced ninhydrin and DFO develop latent fingerprints with similar sensitivity, the DFO process is much simpler.     

Vacuum metal deposition: factors affecting normal and reverse development of latent fingerprints on polyethylene substrates

Vacuum metal deposition (VMD) is an established technique for the development of latent fingerprints on non-porous surfaces. VMD has advantages over cyanoacrylate fuming, especially in circumstances where prints are old, have been exposed to adverse environmental conditions, or are present on semi-porous surfaces. Under normal circumstances, VMD produces 'negative' prints as zinc deposits onto the background substrate and not the print ridges themselves. A phenomenon of 'reverse' development, when zinc deposits onto the print ridges and not the background, has been reported by many authors but its causes have not been conclusively identified.Four plastic substrates were used in this study and these could be easily divided into two groups based on the types of development observed as the amount of deposited gold was increased. On group I plastics, identified as low-density polyethylene (LDPE), normal development then reverse development and finally no development resulted with increasing gold. On group II plastics, identified as high-density polyethylene (HDPE), normal development then over-development and finally poor-quality normal development resulted with increasing gold. Our results suggest that the difference between these plastic types causes variations in the gold film structure which in turn dictates the nature of the zinc deposition.On group I plastics, the structure and thickness of the gold film has been identified as the critical factor in the occurrence of normal or reverse development. Thin gold films on plastic substrates form small 'clusters' (or agglomerates) rather than the atoms being uniformly spread over the surface. The size and shape of these clusters is critical. Once the clusters reach a certain morphology, they no longer act as nucleation sites for zinc, and hence, zinc will not deposit onto the substrate.On group II plastics, results suggest that the gold clusters are smaller and more densely packed. Hence, even though the same amount of gold has been deposited, the gold clusters in this case do not reach the critical morphology and so continue to act as nucleation sites for zinc.Typically, zinc will not deposit onto the fingerprint ridges as the gold nucleation sites are buried within the print residue. However, when more gold is deposited, gold emerges at the surface of the latent print allowing zinc deposition onto the ridges.The rate of gold evaporation was found not to affect the structure of the gold film, although a slower rate of evaporation resulted in more effective deposition.     

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.     

The influence of polymer type, print donor and age on the quality of fingerprints developed on plastic substrates using vacuum metal deposition.

This study investigated fingerprint development on five different polymer substrates using vacuum metal deposition (VMD). The conditions required for optimum development are shown to depend on a number of factors. No one set of conditions will result in good development in all situations. Polymer type has been confirmed as a major factor in determining the types of development that will occur and the optimum VMD conditions required. For more consistently successful VMD development, polymer type should be determined before selecting conditions. While polymer type is a key factor in determining optimum development conditions, there may be variation of the optimum conditions within a polymer type, most likely due to the presence of additives in the plastic. The heaviness of a latent print, i.e. amount of residue that constitutes the print, also affects the VMD conditions required. The donor, manner of deposition, and age of a print affect the heaviness of the deposit. The heavier the print, the higher the gold count necessary for successful VMD development. The occurrence of 'empty prints' (i.e. zinc deposition on the general background but not on or between the print ridges) was found to be related to polymer type and print heaviness. Heavy prints on PVC and PET are the most likely to be 'empty' after VMD treatment. The development of empty prints may be due to the diffusion of print residue into the print valleys. Pre-treatment with cyanoacrylate fuming was also found to affect VMD development. In particular, it was shown that cyanoacrylate pre-treatment was beneficial for print development on PET and PVC. The results of this study were used to formulate guidelines for use as an aid by laboratories using VMD in casework.