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).     

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.     

Chemical development of latent fingerprints: computational design of ninhydrin analogues

The design of chemical compounds for development of latent fingerprints is explored computationally. Our main findings are: (a) We show why past attempts to improve the widely used ninhydrin gave relatively small improvements (referring to color only). The optical transition is connected with a "transition core" and therefore is influenced little by substitution on the aromatic rings. (b) We propose new analogues of ninhydrin with a significant potential such as thiono derivatives.     

京尼平与茚三酮显现手印方法的比较研究

目的对京尼平与茚三酮两种手印显现方法进行综合评价。方法用两种方法显现不同遗留客体上不同遗留时间的手印,并对显现效果、显出手印的稳定性及纸张字迹油墨扩散等现象进行考察。结果京尼平与茚三酮有着相似的的显现原理、适用范围和熏显条件,但在显现效果、显出手印稳定性、试剂成本和安全性能方面存在差异。结论京尼平相比茚三酮方法更安全、绿色环保、显出的手印稳定性更强。     

Reagents for the chemical development of latent fingerprints: scope and limitations of benzo[f]ninhydrin in comparison to ninhydrin

Benzo[f]ninhydrin was compared to ninhydrin for fingerprint development on paper. Overall, the performance of ninhydrin on exhibits was slightly better than that of benzo[f]ninhydrin. The significant advantages of the benzo[f]ninhydrin over ninhydrin were the much stronger fluorescence it gave after treatment with zinc salts and a slightly quicker reaction under ambient conditions. This fluorescence is, however, similar to that obtained with other reagents, such as DFO or ninhydrin analogs. These advantages apparently are not sufficient to justify regular usage of benzo[f]ninhydrin, especially when one considers its low solubility and high cost.     

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

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.     

茚三酮显现汗潜指印的三种操作方法对DNA检测的影响

目的探讨并比较茚三酮显现汗潜指印的3种操作方法,即溶液浸泡法、涂抹法和喷雾法对后续DNA检测带来的影响。方法取16名志愿者的指印分4组,分为茚三酮浸泡法、涂抹法和喷雾法以及空白组,然后提取DlNA进行定量和STR分型检测。结果3种操作方法都会减少汗潜指印DNA的量,喷雾法的损失量最大,浸泡法和涂抹法结果比较接近。结论现场可疑指印检材,应根据检验需要决定指印显现和DNA提取的先后顺序。     

硝酸银、茚三酮、DFO法显现纸张上指印的效果比较

目的为有效的提高纸张上汗潜手印的显现率。方法根据汗潜手印的显现原理,针对不同的纸张,分别运用硝酸银、茚三酮与DFO（1,8-二氮芴-9-酮）3种显现方法进行了实验,并对实验结果进行了分析比较。重点分析了这3种方法在显现不同纸张、不同遗留时间、不同汗液量的汗潜手印时的效果及其适用范围。结果为改善渗透性客体上的汗潜手印显现效果,提供科学的依据。     

Latent fingermark development on a range of porous substrates using ninhydrin analogs--a comparison with ninhydrin and 1,8-diazofluoren

Three relatively new reagents for developing latent fingermarks on porous substrates, 1,2-indandione (IND), 5-methylthioninhydrin (5-MTN), and lawsone, are compared with the more widely used ninhydrin and 1,8-diazofluoren (DFO). Developed latent fingermark visualization on 10 different substrates comprising colored papers, cardboard, and cellophane rather than conventional printer and writing/notepad paper is assessed using latent fingermark deposits from 48 donors. Results show improved fluorescent fingermark visualization using IND compared with DFO on a range of colored cardboards and thick white paper, thus extending the range of substrates known to yield improved visualization with IND. Adding zinc chloride to IND failed to yield any further improvement in fluorescent fingermark visualization. 5-MTN (with and without zinc chloride posttreatment) showed no improvement in visualization compared with ninhydrin and DFO although visible fingermarks were developed. Lawsone produced fluorescent visible fingermarks only with white substrates, which were inferior to those produced with DFO.     

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.     

On the detection of fingerprints by laser excited luminescence

Two surveys were carried out to determine the percentage of latent fingerprints detectable by their inherent luminescence under laser illumination. Less than one-fifth of 240 samples each containing four prints on paper gave luminescent prints. The luminescence from these was weak and only detectable under close scrutiny. Similar results were obtained for 120 samples each containing one print on glass. Forty-one of the samples showing no luminescence were sprayed, approximately one month after deposition, with a solution containing the fluorescent tagging agent 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD chloride). After treatment with NBD chloride, 37 of these samples gave luminescent prints, many of which were intensely luminescent and contained good ridge detail.     

纳米材料在潜指纹显现中的应用

本文综述了纳米材料以均匀分散的液体或粉末形式在法庭科学潜指纹显现领域的研究现状,重点阐述了金属纳米材料、金属氧化物纳米材料及半导体纳米材料显现多种遗留客体上不同状况的潜指纹,并对纳米材料在法庭科学领域的应用前景进行了展望。     

Visualizing latent fingerprints on color-printed papers using ultraviolet fluorescence

Laser detection of latent fingerprints on a white paper has been performed, previously. Ultraviolet fluorescence from various kinds of printer toner and ink used for home printers were measured to study fluorescence imaging of fingerprints on a color-printed white paper. The experimental system consisted of a nanosecond pulsed tunable laser and a cooled CCD camera. Excitation wavelengths are 230 and 280 nm. Fourteen printers consisting of three color laser printers, three color inkjet printers, five monochrome laser printers, two monochrome copy machines, and a color copy machine were tested. Toner and ink of most printers exhibited fluorescence in the region from 360 to 550 nm. In most cases, clear fluorescence images were obtained by time-resolved imaging with a band-pass filter and 280-nm excitation. However for toners from laser color printers that showed strong fluorescence, better results were obtained with 230-nm excitation. Latent fingerprints on a photograph page and a black-character page of a newspaper were also imaged.     

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.     

Some observations on Japanese and American policing

The highly successful Japanese and less than successful American policing situations were compared in terms of: historical background, police organization and format, cultural environment, social-cultural background of officers. training, police socialization, and general nature of policing. Positive influences upon Japanese policing were found to be: the nature of the Japanese people; their deliberate recruitment of ideal police candidates—especially recruiting from samurai families; the highly respected paternalistic and benevolent image in Japan of the police as governmental officials; their deliberate socialization of officers into the police fraternity by using pride. duty, and responsibility to ensure professionalism; and their very extensive and thorough academy training in continuity with later field training and performance. It was suggested that in the United States we begin to address our problems in both selection and training by formulating and then enforcing national guidelines similar to those in Japan.     

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.     

紫外光谱成像技术显现潜在油汗混合指印的初步探索

目的研究运用紫外光谱成像技术显现潜在油汗混合指印的可行性和方法。方法使用紫外光谱成像仪获取典型潜在油汗混合指印的光谱影像数据资料,比较不同数据处理软件的分析结果。结果紫外光谱成像技术具有显现潜在油汗指印的能力。结论紫外光谱成像技术能够成功显现非渗透性客体表面潜在油汗混合指印。