A further study to investigate the detection and enhancement of latent fingerprints using visible absorption and luminescence chemical imaging

This study investigated the application of chemical imaging to the detection of latent fingerprints using the Condor macroscopic chemical imaging system (ChemImage Corp., Pittsburgh, USA). Methods were developed and optimised for the visualisation of untreated latent fingerprints and fingerprints processed with DFO, ninhydrin, cyanoacrylate, and cyanoacrylate plus rhodamine 6G stain. The results obtained with chemical imaging were compared to the detection achieved using conventional imaging techniques. The Condor significantly improved the detection of many prints, especially those that might be considered poor quality or borderline prints. Prints on newspaper treated with ninhydrin and DFO, and prints on white and yellow paper treated with ninhydrin, benefited the most from chemical imaging detection. In many cases, fingerprints undetectable using conventional imaging techniques could be visualised with chemical imaging. Ridge detail from untreated prints on yellow paper was also detected using the Condor. When prints of high quality were examined, both detection techniques produced quality results. The results of this project demonstrate that chemical imaging offers advantages over conventional visualisation techniques when examining latent fingerprints, especially those that would be considered difficult, such as weak prints or prints on surfaces that produce highly luminescent backgrounds. Standard testing procedures for the detection and enhancement of fingerprints by chemical imaging are presented and discussed.     

A Modified Electrostatic Adsorption Apparatus for Latent Fingerprint Development on Unfired Cartridge Cases

Visualization of latent fingerprints on metallic surfaces by the method of applying electrostatic charging and adsorption is considered as a promising chemical‐free method, which has the merit of nondestruction, and is considered to be effective for some difficult situations such as aged fingerprint deposits or those exposed to environmental extremes. In fact, a portable electrostatic generator can be easily accessible in a local forensic technology laboratory, which is already widely used in the visualization of footwear impressions. In this study, a modified version of this electrostatic apparatus is proposed for latent fingerprint development and has shown great potential in visualizing fingerprints on metallic surfaces such as cartridge cases. Results indicate that this experimental arrangement can successfully develop aged latent fingerprints on metal surfaces, and we demonstrate its effectiveness compared with existing conventional fingerprint recovery methods.     

胺端基型CdS／PAMAM潜在显现指印的应用

目的探索一种新型纳米荧光材料的制备方法及其在潜在指印显现方面的应用前景。方法以聚酰胺-胺（PAMAM）树形分子为模板，原位合成CdS纳米簇。并使用荧光光谱法对产物进行表征：应用这种新型荧光材料对多种客体表面、不同陈旧程度的潜在指印进行显现．并将显现结果与传统荧光染料进行比对。结果该荧光材料在365nm紫外光激发下可以发出很强的可见荧光：与传统的荧光染料相比。-NH2端基型CdS／PA—MAM可以同指印残留物进行靶向结合．其荧光强度高、背景干扰小，指印纹线与客体反差大。结论-NH2端基型CdS／PAMAM可以有效地显出非渗透性客体表面的潜在指EP。     

The application of infrared chemical imaging to the detection and enhancement of latent fingerprints: method optimization and further findings

Fourier transform infrared (FTIR) chemical imaging allows the collection of fingerprint images from backgrounds that have traditionally posed problems for conventional fingerprint detection methods. In this work, the suitability of this technique for the imaging of fingerprints on a wider range of difficult surfaces (including polymer banknotes, various types of paper, and aluminum drink cans) has been tested. For each new surface, a systematic methodology was employed to optimize settings such as spectral resolution, number of scans, and pixel aggregation in order to reduce collection time and file-size without compromising spatial resolution and the quality of the final fingerprint image. The imaging of cyanoacrylate-fumed fingerprints on polymer banknotes has been improved, with shorter collection times for larger image areas. One-month-old fingerprints on polymer banknotes have been successfully fumed and imaged. It was also found that FTIR chemical imaging gives high quality images of cyanoacrylate-fumed fingerprints on aluminum drink cans, regardless of the printed background. Although visible and UV light sources do not yield fingerprint images of the same quality on difficult, nonporous backgrounds, in many cases they can be used to locate a fingerprint prior to higher quality imaging by the FTIR technique. Attempts to acquire FTIR images of fingerprints on paper-based porous surfaces that had been treated with established reagents such as ninhydrin were all unsuccessful due to the swamping effect of the cellulose constituents of the paper.     

PAMAM G7.0的制备及在非渗透性表面手印显现中的应用

目的探索一种非渗透性表面手印显现的新方法。方法根据现有方法合成第七代聚酰胺-胺（PAMAM G7.0）树形分子材料,并使用荧光光谱法对产物进行荧光测试;将合成材料对多种客体表面、不同遗留时间的手印进行显现,并将显现结果与粉末法和传统的荧光染料法进行比对。结果实验表明该荧光材料在365nm光激发下可以发出较强的可见荧光;与粉末法和传统的荧光染料法相比,PAMAM G7.0可以同手印残留物进行高选择性结合,手印纹线与背景之间的反差大。结论PAMAMG7.0可以有效地显出非渗透性客体表面的手印。     

基于PolyCyano UV粉末显现手印的新技术

目的介绍1种新型PolyCyano UV粉末显现非渗透性光滑客体表面潜手印的新技术。方法选取多种常见客体,由志愿者在客体上捺印指印,将PolyCyano UV粉末加热至230℃使其升华,待该粉末在手印纹线上聚合后使用长波紫外线照射若干时间,然后在蓝光激发下使用滤色镜观察并拍照。结果绝大部分非渗透性光滑客体表面上的潜手印均有很好的显现效果,尤其是对浅色或白色客体有十分明显的荧光效果,对陈旧手印也有较好的显现效果。结论该方法熏显操作简便、显现时间短、无需二次染色增强、不破坏生物检材、显现效果明显,适合推广使用。     

Optimization and initial evaluation of 1,2-indandione as a reagent for fingerprint detection

1,2-Indandione has been used to develop fluorescent fingerprints on porous materials such as paper. The compound reacts with amino acid residues to produce highly fluorescent fingerprint ridges. An optimized formulation and treatment protocol for using the reagent is presented here. The reagent is applied as a solution in HFE7100 containing acetic acid and ethyl acetate. Treated articles are heated at 100 degrees C for 10 min at ambient humidity and stored in the dark before recording the fingerprints using fluorescence photography or digital imaging. Photodecomposition of the fluorescent fingerprints has been observed. Storage in the dark reduces degradation, extending the lifetime of the fingerprints. Other chemical methods to stabilize the fingerprints proved unsuccessful. Comparisons of the performance of 1,2-indandione with DFO in CFC113 performed on a limited range of substrates indicated that the reagent might be an effective method for the development of latent fingerprints despite the new reagent producing less intense fluorescence.     

A scanning beam time-resolved imaging system for fingerprint detection

A highly sensitive confocal scanning-beam system for time-resolved imaging of fingerprints is described. Time-resolved imaging is a relatively new forensic procedure for the detection and imaging of latent fingerprints on fluorescent substrates such as paper, cardboard, and fluorescent paint. Ordinary fluorescent imaging of latent fingerprints on these surfaces results in poor contrast. Instead, the specimens are treated with a phosphorescent dye that preferentially adheres to the fingerprint which allows time-resolved discrimination between the fingerprint phosphorescence and the background fluorescence. Time resolved images are obtained by synchronizing the digital sampling of the specimen luminescence with the on-off cycle of the chopped illumination beam. The merit of this technique is illustrated with high contrast images of fingerprints obtained from the fluorescent painted surface of a Coke can.     

Effects of CBRN Decontaminants in Common use by First Responders on the Recovery of Latent Fingerprints—Assessment of the Loss of Ridge Detail on Glass

Following a CBRN incident, first responders use decontamination procedures to reduce the risk of exposure. The effect of decontamination on forensic trace material has, however, not been fully examined. This study sought to evaluate the effect of five different physical or chemical decontamination materials on the recovery of latent fingerprints. Fingerprints were deposited on glass slides, decontaminated, and assessed on the presence of ridge detail. The results demonstrate that decontamination affects the quality of latent fingerprints substantially. On at least 61% of the fingerprints, a reduced amount of ridge detail was observed upon decontamination. Furthermore, development with cyanoacrylate appeared not to succeed anymore. Instead, the ability of vacuum metal deposition to successfully develop decontaminated fingerprints is demonstrated. The results from this study may contribute to an increased forensic awareness regarding decontamination and emphasize the necessity for further research into new item decontamination procedures or new forensic initiatives prior to decontamination.     

Characterization of Digital Cameras for Reflected Ultraviolet Photography; Implications for Qualitative and Quantitative Image Analysis During Forensic Examination

Reflected ultraviolet imaging techniques allow for the visualization of evidence normally outside the human visible spectrum. Specialized digital cameras possessing extended sensitivity can be used for recording reflected ultraviolet radiation. Currently, there is a lack of standardized methods for ultraviolet image recording and processing using digital cameras, potentially limiting the implementation and interpretation. A methodology is presented for processing ultraviolet images based on linear responses and the sensitivity of the respective color channels. The methodology is applied to a FujiS3 UVIR camera, and a modified Nikon D70s camera, to reconstruct their respective spectral sensitivity curves between 320 and 400 nm. This method results in images with low noise and high contrast, suitable for qualitative and/or quantitative analysis. The application of this methodology is demonstrated in the recording of latent fingerprints.     

上转换发光微粒悬浮液显现手印技术初探

目的 建立NaYF4∶Er,Yb微粒悬浮液显现手印技术方法并界定适用范围与条件.方法 用NaYF4∶Er,Yb微粒悬浮液显现瓷砖、玻璃等19种（各50枚）不同客体上皮脂汗手印,并对结果进行分析比较.结果 该方法对背景复杂的非渗透性客体上的油汗手印显现良好,其效果优于普通ZnO小颗粒悬浮液.结论 该方法操作简便、适用客体广泛、背景干扰少,适合进一步研究推广.     

碘热升华喷枪显现潜手印的应用研究

本文提出一种以石英灯为加热器的碘热升华喷枪显现潜手印的新方法。实验表明,该技术方法操作简便,适用范围广,手印显出率高,尤其是显现遗留在墙面、本色铝合金表面、UPVC表面的潜手印效果明显。     

Advanced solvent-free application of ninhydrin for detection of latent fingerprints on thermal paper and other surfaces

This work presents the first known experiments of ninhydrin sublimation in vacuum to detect latent fingerprints on thermal paper. In this method, latent fingerprints become visible in rich detail without the background black staining known from the application of ninhydrin solutions to thermal paper. The method involves hanging the thermal paper samples 15 cm above a heating source with dispersed ninhydrin crystals in a vacuum chamber. The optimized conditions for ninhydrin sublimation are 50 mg ninhydrin, 2 to 5 mbar vacuum, and 150 degrees C heating source temperature for 30 min. The application of this method is also successful on the new euro notes. Latent fingerprints can be developed across the transitions from paper to optical variable device (OVD).     

Infrared spectroscopic imaging for noninvasive detection of latent fingerprints

The capability of Fourier transform infrared (FTIR) spectroscopic imaging to provide detailed images of unprocessed latent fingerprints while also preserving important trace evidence is demonstrated. Unprocessed fingerprints were developed on various porous and nonporous substrates. Data-processing methods used to extract the latent fingerprint ridge pattern from the background material included basic infrared spectroscopic band intensities, addition and subtraction of band intensity measurements, principal components analysis (PCA) and calculation of second derivative band intensities, as well as combinations of these various techniques. Additionally, trace evidence within the fingerprints was recovered and identified.     

茚三酮固体介质法显现不同纸张表面潜指纹

茚三酮是显现渗透性客体上潜在汗液手印的最常用方法之一,采用微量物证提取纸和茚三酮溶液有机结合制作的茚三酮固体介质可以有效避免客体表面背景着色,不容易引起纸张油墨扩散,另外避免使用的溶剂易燃。能够更便捷的显现现场指纹,并且能够突破茚三酮只能显现渗透性客体的局限,拓宽茚三酮显现客体的范围,在热敏纸上潜指纹的显现方面有独特的应用优势。     

Luminous lip-prints as criminal evidence

Luminescence is specially a useful property for the search of invisible evidences at the scene of a crime. In the latent fingerprints particular case, there are at one's disposal fluorescent reagents for their localization. The study of latent lip prints (that is lip prints from protective lipstick, or permanent or long-lasting lipstick that do not leave any visible marks) is more recent than fingerprints study. Because of the different composition of both types of prints, different reagents have been tried out on their developing. Although, lysochromes are particularly useful reagents to obtain latent lip prints, it may occur on coloured or multicoloured surfaces, the developing is not perceived due to contrast problems between the reagent and the surface where the print is searched. Again, luminescence offers the possibility to solve this problem. Nile Red is being studied as a potential developer for latent lip prints. The results on very old prints (over 1year) indicate that this reagent is highly efficient to get latent lip prints.     

The Use of Liquid Latex to Recover Latent Fingerprints that are Covered in Debris from Exterior Glass Surfaces of Vehicles

The purpose of this research is to determine if latent fingerprints deposited on the exterior glass surfaces of vehicles, then covered in debris, can be recovered. Past research used liquid latex to lift soot to recover trace evidence. Recently, liquid latex has been used to recover latent fingerprints along the bottom of vehicles. In this study, a total of 216 latent fingerprints were deposited on the exterior windows of three vehicles. Three control and three experimental latent fingerprints were placed on each side window. The vehicles collected debris for either 2, 3, or 4 weeks. After debris collection, liquid latex was applied to the experimental sections. The underlying fingerprints were developed with white granular powder. Control fingerprints were developed directly with white granular powder. A chi-square test revealed a significant difference in fingerprint recovery between the control and liquid latex method (X² = 9.026, d.f. = 1, p = 0.003). An odds ratio determined that the control method increases the probability of latent fingerprint recovery by 2.68. Fisher's exact test indicated that there is no statistically significant difference between the detail of the recovered control and experimental fingerprints (p = 0.065). This study demonstrates that recovery of fingerprints is possible using the liquid latex method; however, the control method recovers more fingerprints on the glass exterior of vehicles. If latent fingerprints are thought to be present on the exterior glass surfaces of vehicles, the control method should be used to improve vehicle processing by investigators.     

Visualization of latent fingerprints using fluorescence lifetime imaging on paper emitting strong fluorescence

Latent fingerprints were successfully visualized using fluorescence lifetime imaging (FLIM) on paper which emits strong fluorescence with a lifetime close to that of fingerprints and thus from which it is difficult for time-resolved spectroscopy to visualize fingerprints. Latent fingerprint samples on paper were excited using a 450 nm or 532 nm nanosecond pulsed-laser, and time-resolved fluorescence images were obtained at a delay time of 6–16 ns in intervals of 1 ns, to the excitation pulse. The excitation beam was expanded using a lens, and the fluorescence from the fingerprints was captured using an intensified CCD camera. Because of the large fluorescence intensity of the background paper of approximately two to four orders of magnitude larger than that of the fingerprint, the fingerprint was not visualized on each fluorescence image by time-resolved spectroscopy. However, the fingerprint was visualized in a FLIM image constructed using a series of the fluorescence images for the case with the fluorescence intensity of the background paper being four orders of magnitude larger than that of the fingerprint. The difference in fluorescence lifetime in the FLIM image of the visualized fingerprint and background paper was in the order of 0.1 ns, which was an order of magnitude smaller than the inherent fluorescence lifetime of a few nanoseconds for the fingerprints and paper. It was demonstrated that, at a background fluorescence intensity with a certain order of magnitude larger than that of fingerprints, FLIM has the potential to visualize latent fingerprints which cannot be visualized by time-resolved spectroscopy.     

Diimide-enhanced fingerprint detection with photoluminescent CdS/dendrimer nanocomposites

The chemical development of latent fingerprints by nanocomposites that involve photoluminescent cadmium sulfide nanoparticle aggregates with Starburst dendrimer is demonstrated. The dendrimer bonds to fingerprint residue via its terminal functional groups. When these are amino groups (generation 4 dendrimer), the binding is enhanced by fingerprint pre-treatment with diimide. The diimide converts carboxylic acid moieties of the fingerprint residue to esters that then react with the dendrimer amino groups to form amide linkages. The cadmium sulfide/generation 4 dendrimer development of fingerprints is enhanced by elevated temperature also. Finally, fingerprint development with carboxylate-functionalized cadmium sulfide/generation 3.5 dendrimer nanocomposites is examined. Here, diimide treatment of the dendrimer itself aids the subsequent fingerprint labeling, which involves amino acid of the figerprint residue. Nanocomposite fingerprint detection is compatible with time-resolved imaging for background fluorescence elimination.