The recoverability of fingerprints on paper exposed to elevated temperatures - Part 1: comparison of enhancement techniques

This research investigates the recoverability of fingerprints which have been exposed to elevated temperatures in order to mimic the environment a piece of paper may be exposed to within an arson scene. Arson is an expensive crime, costing the UK economy, on average, £53.8 million each week [1]. Anything which may give rise to the identity of the fire setter should be analysed and as such, unburnt paper may be a potential source of fingerprints. While it is true that even a moderate fire will obscure and render partially useless some types of evidence, many items, including fingerprints, may still survive [2-4]. This research has shown that fingerprints are still retrievable from paper which has been subjected to the maximum testing conditions of 200˚C for 320min. In fact, some fingerprints naturally enhance themselves by the heating process. This investigation has also shown that the most effective enhancement technique was found to be 1,8-diazafluoren-9-one (DFO) for exposure temperatures upto 100˚C. Physical developer (PD) is the most effective enhancement technique for exposure temperatures from 100˚C to 200˚C. For porous surfaces, there are fingerprint development techniques which are effective at enhancing fingerprints exposed upto a temperature of 200˚C, irrespective of the firefighting extinguishing technique, as PD, in addition to developing fingerprints exposed to high temperatures, is one of the few processes which will enhance fingermarks on wetted surfaces

A comparison of six fingerprint enhancement techniques for the recovery of latent fingerprints from unfired cartridge cases

This work compared the effectiveness of six different enhancement methods on six different sizes of brass cartridges. One sebaceous fingerprint was deposited onto twenty-five of each size of cartridge to enable a statistical evaluation of the enhancement methods for each cartridge size to be undertaken. The enhancement methods compared were superglue followed by BY40, superglue followed by gun blue followed by BY40, gun blue only, superglue followed by palladium deposition, palladium deposition only, and powder suspension. The six different cartridges used in this study were .22s, .32s, 9mm, .38s, ribbed shotgun, and smooth shotgun. The study found that more potentially identifiable fingerprints were enhanced on the larger cartridge cases. This was due to the surface area on the smaller cartridges, and in particular the .22s provided little ridge detail. Two techniques provided the best results - superglue followed by gun blue followed by BY40, and superglue followed by palladium deposition. This showed that the combination of the cyanoacrylate fuming and the metal oxidation reactions is increasing the yield of potentially identifiable fingerprints compared with the use of the techniques separately. Both techniques were also found to give reproducible results. These two enhancement techniques were also compared statistically and no statistical difference in their effectiveness was found suggesting both techniques are equally as effective at enhancing fingerprints on brass cartridge cases

The recoverability of fingerprints on paper exposed to elevated temperatures - Part 2: natural fluorescence

Previous work by the authors [1] investigated the recoverability of fingerprints on paper which had been exposed to elevated temperatures by comparing various chemical enhancement techniques (ninhydrin, 1,8-diazafluoren-9-one (DFO), and physical developer (PD)). During that study, it became apparent, as a consequence of observations made in operational work [2], that fingerprints on paper subjected to 150˚C fluoresced under examination with green light of waveband 473-548nm with a 549nm viewing filter. This work examined the three types of prints (eccrine, sebaceous, and ungroomed) after 20 min exposure to the temperature range 110˚C to 190˚C (in 10˚C increments) and found that the eccrine fingerprints fluoresced more brightly. This indicated that it was a component of the eccrine deposit which was causing the fluorescence. Luminance measurements found that the maximum fluorescence was experienced at 170˚C on both types of paper. As a consequence, eccrine heat-treated fingerprints were viewed under violet-blue (350-469nm), blue (352-509nm), and green light (473-548nm) which indicated that the greatest luminance intensities were obtained under blue light and the smallest under green light. In order to determine what component of the eccrine fingerprint was causing this fluorescence, five of the most prevalent amino acids (alanine, aspartic acid, glycine, lysine, and serine) [3-4] were exposed to this temperature range. The luminance measurements were taken under exposure to the green light in order for the minimum fluorescence to be observed, with an assumption that blue-violet or blue illumination will provide brighter fluorescence in practice. The results indicated that four of the amino acids are behaving similarly across the temperature range, but with slightly different luminance measurements, but all are exhibiting some level of fluorescence. Thermal degradation products of alanine and aspartic acid have been suggested by Richmond-Aylor et al. [5]. The structure of these thermal degradation products is cyclic in nature, and as such, there is a possibility that two of these products would fluorescence. Sodium chloride and urea were also exposed to the temperature range and they also fluoresced to some extent. This work shows that eccrine fingerprints that have been exposed to temperatures of between 130˚C to 180˚C will fluoresce under violet-blue, blue, and green light. This level of fluorescence for ungroomed fingerprints is much less but this will be dependent on the individual, the more eccrine the deposit, the stronger the fluorescence. This work shows that the amino acids, sodium chloride, and urea present in fingerprint deposits are all contributing to the fluorescence of the print, but may not be the sole contributor as other eccrine components have not yet been tested

The recoverability of fingerprints on nonporous surfaces exposed to elevated temperatures

Previous work by the authors compared the effectiveness of ninhydrin, 1,8-diazafluoren-9-one (DFO), and physical developer (PD) as enhancement reagents for fingerprints deposited on paper that had been exposed to elevated temperatures. This research extends the previous study and investigates the recoverability of fingerprints deposited onto glass and ceramic surfaces in order to mimic the environment these surfaces may be exposed to within a fire scene. This research has shown that ridge detail is still retrievable from ceramic after exposure to 800 °C (1472 °F) for 20 minutes, although, at temperatures in excess of 350 °C (662 °F), ridge detail would only survive if the fingerprints had been protected from direct exposure to radiant heat and direct air flow across the surface. This investigation has shown that the most effective enhancement technique overall was found to be superglue followed by BY40 at all temperatures except 200 °C (392 °F) in which case, iron powder suspension was superior. However, superglue followed by BY40 may have to be excluded as a prospective enhancement technique for many situations because the nonporous surface may become wet during firefighting activity. The use of silver vacuum metal deposition has been demonstrated to develop fingerprints after exposure to higher temperatures and may have future potential for this application

Search results of heat-distorted fingerprints using sagem metamorpho AFIS

This research investigated the identification of fingerprints which had been distorted by heating the recipient surface. Fingerprints were deposited on uPVC which was then exposed to sufficient heat to cause distortion of the surface. The fingerprints were distorted vertically and horizontally as a consequence of the flow of uPVC resulting from the exposure to heat. Photographic images were taken of the fingerprints before and after distortion and both sets of images where loaded into the Sagem Metamorpho™ AFIS. Successful identifications were obtained in a number of cases. The results indicated that the quality of the fingerprint before heating influenced the identification of the distorted fingerprint. The results also showed that the vertically distorted fingerprints were more readily identified than horizontally distorted fingerprints. This research has shown that successful identifications can be achieved from fingerprints distorted by heat providing the pre heated fingerprint is of good quality

The recoverability of fingerprints on non porous surfaces exposed to elevated temperatures

Previous work by the authors compared the effectiveness of ninhydrin, 1,8-diazafluoren-9-one (DFO), and physical developer (PD) as enhancement reagents for fingerprints deposited on paper that had been exposed to elevated temperatures. This research extends the previous study and investigates the recoverability of fingerprints deposited onto glass and ceramic surfaces in order to mimic the environment these surfaces may be exposed to within fire scene. This research has shown that ridge detail is still retrievable from ceramic after exposure to 800˚C (1472˚F) for 20min, although it would only survive if the fingerprints had been protected from direct exposure to radiant heat and direct air flow across the surface at temperatures in excess of 350˚C (622˚F). This investigation has shown that the most effective enhancement technique overall was found to be superglue followed by BY40 at all temperatures except 200˚C (392˚F) where iron powder suspension was superior. However, superglue followed by BY40 may have to be excluded as a prospective enhancement technique for many situations as the non porous surface may become wet during firefighting activity. The use of silver vacuum metal deposition has been demonstrated to develop fingerprints after exposure to higher temperatures and may have future potential for this application