A Systematic Study to Understand the Effects of Particle Size Distribution of Magnetic Fingerprint Powders on Surfaces with Various Porosities

This study intends to design magnetite (Fe₃O₄)‐based magnetic fingerprint powders with different particle size distributions. It also investigates the influence of particle size distribution on the visualization of latent fingermarks with as little background staining as possible on the surfaces with various porosities in a systematic way. Two strategies were used to prepare the magnetic fingerprint formulations for this study: milling of coarse magnetite particles for different durations, and mixing of sieved fine particles with different size ranges with coarse particles. Particle size analyses of the prepared magnetic powders, optical microscopy‐based roughness analysis of the surfaces and SEM measurements of the visualized fingerprints and representative powders were performed. Mag2 of the formulations prepared through milling and Mag5 and Mag6 of the formulations prepared through sieving and mixing were more successful in the development of latent prints than the rest of the solutions.     

利用CdSe巯基乙酸溶液显现水浸客体表面潜手印

目的研究水浸客体表面潜指纹的显现方法;方法利用CdSe巯基乙酸溶液显现被水浸泡过的黄色封箱胶带、黑色塑料袋、玻璃等常见非渗透性客体上的潜手印,讨论影响水浸非渗透性客体上潜手印显现效果的各种因素,并与传统方法进行比较,初步探讨了CdSe巯基乙酸溶液显现水浸非渗透性客体表面潜手印的方法;结果使用巯基乙酸包覆CdSe纳米复合材料显现潜在手印,使每分子纳米复合材料外表包覆足够数量的羧基,则可以提高它同手印残留物的结合能力,从而得到更高清晰度、更高分辨率的手印显像;结论巯基乙酸包覆CdSe纳米复合材料可以很好的显现水浸塑料、胶带等表面潜指纹。     

新型亲油性纳米二氧化硅粉末在手印显现中的应用

目的 比较新型亲油性纳米二氧化硅粉末显现手印的效果.方法 应用亲油性纳米二氧化硅粉末与现场勘查箱内金粉、银粉和黑色磁性粉显现非渗透性客体表面油汗混合手印,并在自然光下观察比较显现效果.结果 亲油性纳米二氧化硅粉末显现出的手印图像纹线清晰连贯,背景反差好.结论 亲油性纳米二氧化硅粉末显现手印具有一定的优势.     

Evaluation of Four Fingerprint Development Methods for Touch Chemistry Using Matrix‐Assisted Laser Desorption Ionization/Time‐of‐Flight Mass Spectrometry,

Four preparation techniques for MALDI/TOF mass spectrometry were compared to determine the ability to gather intelligence for investigations through the chemical analysis of latent fingerprints, defined as “touch chemistry.” Compatible fingerprint development processes used for identification along with new techniques are necessary to evaluate touch chemistry. Ten volunteers deposited fingerprints from solvent residues containing drugs and explosives onto microscope slides. The developers included (A) fingerprint powder, (B) MALDI matrix, (C) fingerprint powder and lifting, and (D) cyanoacrylate fuming with fingerprint powder. Qualitative identification was based on ion images and spectra. The highest average detection rates (88%) were found using methods A and B. Methods C (52%) or D (18%) had limited success. Results demonstrate the importance of imaging coupled to extracted mass spectral data in detecting analytes in deposited fingerprints. Overall, the results suggest continued development of touch chemistry applications could prove useful for gathering intelligence and forensically relevant information.     

A Simple Computer‐assisted Quantification of Contrast in a Fingerprint

A simple method for quantification of contrast in a fingerprint is proposed. Contrast is defined as the average difference in intensity of pixels between valleys and ridges in a fingerprint. It is quantified from a scanner‐acquired image of the fingerprint using a histogram function of Adobe Photoshop. The method was validated with black inked prints and marks developed with aluminum powder. Moreover, we tested resistance of the method to rater‐dependent errors and dependence of the measurements on the resolution of an image and the model of the scanner. For both groups of fingerprints, the method gave coherent and easily interpretable quantitative values for contrast. There were no significant differences between measurements performed by different raters and by the same rater in a test–retest procedure. However, the method was found to be instrument dependent, as measurements were significantly affected by image resolution and the model of the scanner.     

The use of liquid latex as a pre-treatment to recover debris-covered latent fingerprints from exterior surfaces of vehicles

This study evaluated the effectiveness of using liquid latex as a pre-treatment for fingerprint recovery from the exterior surfaces of vehicles in summer. The sample of this study was 540 sebaceous latent fingerprints deposited on the lower body of three vehicles. Thirty control and thirty experimental fingerprints were deposited on each vehicle, and the experiment was repeated three times. The three vehicles were driven daily for either 2, 3, or 4 weeks after the deposition of fingerprints. After the vehicles reached their designated debris accumulation duration, the latent fingerprints in the control groups were developed with black fingerprint powder. Liquid latex was applied onto the fingerprints in the experimental groups, and they were subsequently developed with black fingerprint powder. A chi-sure test indicated that there was a significant difference in fingerprints recovery performance between two methods (X² = 4.903, d.f. = 1, p = 0.027). An odds ratio test indicated the control method increases the probability of fingerprint recovery by 1.54 times. A Fisher's exact test was used to evaluate the quality of fingerprints recovered from both methods and it indicated that there is no significant difference in quality using the two methods (p = 0.058). This study indicated that the traditional fingerprint powder method performed better for fingerprint recovery from exterior surfaces of vehicles in summer.     

Lifting techniques for finger marks on human skin previous enhancement by Swedish Black powder — A preliminary study

An examination was done to investigate whether certain lifting techniques can lift recovered latent fingerprints on human skin surfaces of living subjects. For recovery Swedish Soot powder mixture (Swedish Black) was used.Donors intentionally placed fingerprints on the skin surface of living subjects. Finger marks were then in all cases recovered with Swedish Black powder. The procedure was repeated after 1 h and 4 h. Treated finger marks were secured and preserved as latent fingerprint evidence by different lifting processes. Having examined skin surfaces and finger marks we observed that the lifters such as white instant lifter, white fingerprint gelatin, black fingerprint gelatin, silicone, transparent adhesive tape, are suitable. Moreover, white fingerprint gelatin and white instant lifter proved to be very good at lifting treated finger marks. Black fingerprint gelatin was very good also, but finger marks were examined by slant light.     

浅色调湿粉显现手印方法的研究

目的探索新的手印显现方法,祛除传统手印显现方法对使用者的健康危害;方法用浅色调湿粉采用不同操作对不同客体表面手印、不同物质手印及不同遗留时间手印进行显现,通过显现效果的比较,得出湿粉显现手印的适用范围、最佳操作方法及其显现效果;结果显出的手印清晰、流畅,与背景反差强;结论该方法适用于光滑非渗透性客体表面及潮湿或粘性表面的汗潜、油潜、蛋白手印的显现,使用方便有效。     

Recovery of Latent Fingerprints and DNA on Human Skin*

Abstract: The project “Latent Fingerprints and DNA on Human Skin” was the first systematic research in Europe dealing with detection of fingerprints and DNA left by offenders on the skin of corpses. One thousand samples gave results that allow general statements on the materials and methods used. The tests were carried out according to a uniform trial structure. Fingerprints were deposited by natural donors on corpses. The latent fingerprints were treated with magnetic powder or black fingerprint powder. Afterward, they were lifted with silicone casting material (Isomark^®) or gelatine foil. All lifts were swabbed to recover DNA. It was possible to visualize comparable and identifiable fingerprints on the skin of corpses (16%). In the same categories, magnetic powder (18.4%) yielded better results than black fingerprint powder (13.6%). The number of comparable and identifiable fingerprints decreased on the lifts (12.7%). Isomark^® (14.9%) was the better lifting material in comparison with gelatine foil (10.1%). In one‐third of the samples, DNA could be extracted from the powdered and lifted latents. Black fingerprint powder delivered the better result with a rate of 2.2% for full DNA profiles and profiles useful for exclusion in comparison with 1.8% for the magnetic powder traces. Isomark^® (3.1%) yielded better results than gelatine foil (0.6%).     

Visualization of latent fingerprint corrosion of metallic surfaces

Abstract:  Chemical reactions between latent fingerprints and a variety of metal surfaces are investigated by heating the metal up to temperatures of ∼600°C after deposition of the fingerprint. Ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The degree of fingerprint enhancement appears independent of the elapsed time between deposition and heating but is very dependent on both the composition of the metal and the level of salt secretion by the fingerprint donor. Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge. The corrosion of the metal surface is further exploited by the demonstration of a novel technique for fingerprint enhancement based on the electrostatic charging of the metal and then the preferential adherence of a metallic powder to the corroded part of the metal surface.     

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.     

Initial Results on the Composition of Fingerprints and its Evolution as a Functionof Time by GC/MS Analysis

Abstract: Determining the time since deposition of fingermarks may prove necessary to assess their relevance to criminal investigations. The crucial factor is the initial composition of fingermarks, because it represents the starting point of any aging model. This study mainly aimed to characterize the initial composition of fingerprints, which show a high variability between donors (inter‐variability), but also to investigate the variations among fingerprints from the same donor (intra‐variability). Solutions to reduce this initial variability using squalene and cholesterol as target compounds are proposed and should be further investigated. The influence of substrates was also evaluated, and the initial composition was observed to be larger on porous surface than nonporous surfaces. Preliminary aging of fingerprints over 30 days was finally studied on a porous and a nonporous substrate to evaluate the potential for dating of fingermarks. Squalene was observed to decrease in a faster rate on a nonporous substrate.     

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.     

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.     

Evaluation of DNA Extraction Methods for Processing Fingerprint Powder-Coated Forensic Evidence

In unison, fingerprinting and DNA analysis have played a pivotal role in forensic investigations. Fingerprint powders that are available on the market can come in a range of colors and with specific properties. This study evaluated the efficiency of DNA extraction from samples coated with 3 brands of fingerprint powders: Lightning, Sirchie, and SupraNano, covering a range of colors and properties. A total of 23 fingerprint powders were tested using the Chelex, Promega DNA IQ™, and Applied Biosystems™ PrepFiler™ DNA extraction protocols. The DNA IQ™ and PrepFiler™ methods extracted higher yields of DNA in comparison to Chelex, which also accounted for better quality of PowerPlex x00AE; 21 DNA profiles recovered. There were no signs of degradation or inhibition in the quantification data, indicating that samples returning low DNA yield was due to interference during DNA extraction and not PCR inhibition. DNA profiles were recovered from the majority of fingerprint powders with only a single powder, Sirchie Magnetic Silver, failing to produce a profile using any of the methods tested. A link was observed between the DNA extraction chemistry, fingerprint powder property, that is, nonmagnetic, magnetic and aqueous, and the brand of fingerprint powder. Overall, the DNA IQ™ method was favorable for nonmagnetic fingerprint powders, while magnetic fingerprint powders produced more DNA profiles when extracted with the PrepFiler™ chemistry. This study highlights the importance of screening DNA extraction chemistries for the type of fingerprint powder used, as there is not a single DNA extraction method that suits all fingerprint powder brands and properties.     

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.     

荧光二氧化硅纳米粒子的制备及在手印显现中的应用

目的制备二氧化硅纳米粒子并探索其在手印显现中的应用。方法先制备亲油性二氧化硅纳米粒子,然后加入不同的荧光物质,通过控制变量法筛选出最佳的纳米粉末与荧光粉末的质量比。将制备出的荧光二氧化硅纳米粉末与纳米粉末、荧光粉末进行手印显现效果的比较。结果荧光二氧化硅纳米粒子对多种不同载体表面的潜手印有良好的显现效果。结论荧光二氧化硅纳米粉末与传统粉末相比,在显现有背景干扰客体上的手印有明显优势;与普通荧光粉末相比,荧光二氧化硅纳米粉末具有与手印物质结合效果好,毒性小,不易刷糊,成本低的优势。     

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。     

Contactless Visualization of Latent Fingerprints on Nonporous Curved Surfaces of Circular Cross Section—A Statistical Evaluation on the Materials as Plane Mirror

A new contactless technique for latent fingerprint visualization on nonporous curved surfaces of circular cross section was introduced by Low et al. (1). The technique utilizes a plane mirror to convey the light rays toward the inspected surfaces for latent fingerprint visualization. This research activity came up as an extension of the previous study which utilized an aluminum plate as the plane mirror to illuminate the inspected surfaces. Dulling spray was used to increase the diffuse component of the reflective aluminum plate. However, the amount of dulling spray will affect the uniformity of the illumination on the inspected curved surfaces. In this study, a study on the new materials for the plane mirror was carried out. Coated aluminum, opal, and ground glass diffusers were selected as the new materials. The performance of the new materials was compared to the aluminum based on the quality of the captured images on various nonporous cylindrical surfaces. A statistical approach known as randomized complete block design was used to design the experiment. The quality of the captured images was obtained using Spectral Image Validation and Verification. Two‐way analysis of variance and Fisher's least significant difference test were used to analyze the quality of the images. From the results of the statistical analysis, coated aluminum has the best performance compared to aluminum, opal, and ground glass diffusers.     

Development of Latent Fingermarks on Various Surfaces Using ZnO‐SiO2 Nanopowder

Fingermarks are one of the most useful forms of evidence in identification and can provide generalized proof of identity in crime investigation. They are developed using various conventional powders. The novel nanopowder ZnO‐SiO₂ was synthesized via the conventional heating method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy‐dispersive X‐ray (EDX) analysis, transmission electron microscope (TEM), and X‐ray diffraction (XRD). The mean particle size of ZnO‐SiO₂ nanopowder calculated through TEM was 32.9 nm. The development of fingermarks was carried out by powder dusting and small particle reagent (SPR) methods. Powder dusting method was used for the development of latent fingermarks on various dry, nonporous, and semi‐porous surfaces. The SPR method was also applied to wet nonporous surface. The developed latent fingermarks using ZnO‐SiO₂ nanopowder were found to have excellent quality with very clear third‐level ridges detail and had better visibility than commercially available white powder.