Source Camera Identification for Heavily JPEG Compressed Low Resolution Still Images*

Abstract: In this research, we examined whether fixed pattern noise or more specifically Photo Response Non‐Uniformity (PRNU) can be used to identify the source camera of heavily JPEG compressed digital photographs of resolution 640 × 480 pixels. We extracted PRNU patterns from both reference and questioned images using a two‐dimensional Gaussian filter and compared these patterns by calculating the correlation coefficient between them. Both the closed and open‐set problems were addressed, leading the problems in the closed set to high accuracies for 83% for single images and 100% for around 20 simultaneously identified questioned images. The correct source camera was chosen from a set of 38 cameras of four different types. For the open‐set problem, decision levels were obtained for several numbers of simultaneously identified questioned images. The corresponding false rejection rates were unsatisfactory for single images but improved for simultaneous identification of multiple images.     

Visualization of Latent Fingerprint Corrosion on a Discharged Brass Shell Casing

Abstract:  Latent fingerprint visualization on discharged shell casings can provide good forensic evidence, particularly if the casing is recovered at the scene of a crime where a firearm has been discharged. Unfortunately, visualization of such latent fingerprints when they were deposited prior to discharge of the firearm is problematic as both increased temperature and abrasive friction can inhibit fingerprint visualization with conventional techniques. We present a case study that demonstrates latent fingerprint visualization on a discharged shell casing recovered 14 years ago from the scene of a homicide. Previous cyanoacrylate fuming of the casing had failed to reveal any fingerprints. We use a visualization technique in which a conducting carbon powder adheres preferentially to latent fingerprint corrosion of the casing surface, following the application of a potential of 2.5 kV to the casing. This technique presents opportunities for the review of old cases and for consideration of its use in current cases.     

Visualization of Latent Fingerprint Corrosion of Brass

Abstract:  Visualization of latent fingerprint deposits on metals by enhancing the fingerprint-induced corrosion is now an established technique. However, the corrosion mechanism itself is less well understood. Here, we describe the apparatus constructed to measure the spatial variation (Δ V ) in applied potential ( V ) over the surface of brass disks corroded by latent fingerprint deposits. Measurement of Δ V for potential of 1400 V has enabled visualization of fingerprint ridges and characteristics in terms of this potential difference with Δ V typically of a few volts. This visualization is consistent with the formation of a Schottky barrier at the brass-corrosion product junction. Measurement of the work function of the corroded brass of up to 4.87 ± 0.03 eV supports previous results that suggested that the corrosion product is composed of p-type copper oxides. A model for the galvanic corrosion of brass by ionic salts present in fingerprint deposits is proposed that is consistent with these experimental results.     

浅谈手印DNA技术

手印是犯罪现场上重要而又常见的痕迹物证之一,素有“证据之首”之美称。随着生物DNA技术的不断发展．从现场手印中提取到DNA已成为可能。但目前的手印DNA技术仍然面临着很多困难和挑战,在一定程度上阻碍了其发展。随着DNA的提取和分型扩增技长以及计算机信息技拳的不断发展,手印DNA技术将会给招纹学带来前所未有的飞跃。     

氨基黑显现常见客体上潜血足迹研究

目的研究氨基黑显现潜血足迹所适用的常见客体。方法选择14种常见客体,制作潜血足迹样本,用氨基黑进行显现。结果浅色非渗透性客体的效果优于其他客体。结论氨基黑可以很好的显出某些渗透性客体和非渗透性客体表面的潜血足迹。     

Development of Latent Fingermarks on Surfaces of Food‐A More Realistic Approach

Latent fingermark developing methods from food (mandarin, egg, banana, apple, potato, carrot, eggplant, onion, bell pepper, and tomato) surface has been studied by 10 methods, including powdering method, small particle reagent method, and cyanoacrylate fuming method. The foods were stored under two conditions (room temperature and refrigerator) before fingermark deposition and aged for 2, 24, 48, and 72 h before fingermark development. In most of the food surfaces used in this study, cyanoacrylate fuming with 80% relative humidity was superior to the powder or small particle reagent methods. The quality of the fingermarks varied depending on the storage conditions before the fingermark deposition (in the refrigerator or at ambient temperature) and the time elapsed since the fingermark deposition. However, the storage conditions before the fingermark deposition and the time elapsed since the fingermark deposition did not show any correlation with the quality of the fingermark.     

Fixing Transient Iodine on Developed Latent Fingermarks

In the present study, a simple and novel fume–mist technique is described which can be used efficiently to fix the latent fingermarks developed using iodine. It is well known that the residues left over in the fingermarks interact with iodine to give transient brown impressions which disappear in a short time. Also, iodine forms colored complexes with various organic solvents. Based on iodine–fingermark interaction and iodine–solvent complex formation, latent fingermarks were developed on paper surface using iodine fumes which were subsequently fixed by spraying polar and nonpolar solvents. The fingermarks developed with this technique were not only clear but also permanent in nature. The interaction of fingermark residue, iodine, and solvent forming a ternary structure is believed to be a possible reason for the stability of iodine‐developed fingermarks. Ease of method, availability of chemicals, and minimum training make the method adaptable in routine development of forensic fingermarks present on paper surface.     

Faux Blood Fingermark on Pistol: Latent Fingerprint Developed by Whole Blood

We present a case of a faux blood fingermark, wherein a natural latent fingerprint on the pistol at the crime scene was enhanced by the whole blood of the victim. A male was shot to death. The crime scene investigator did not find any blood fingermark during the collection of evidence, but a blood fingerprint was noticed in the firearms examination. We identified that the fingerprint was of the victim; a series of experiments on the nonporous substrate were then conducted; the death in this case was classified as a suicide. The phenomenon is interesting, and thus, calls for attention of the forensic community.     

Ridge Width Correlations between Inked Prints and Powdered Latent Fingerprints

A methodology to estimate the time of latent fingerprint deposition would be of great value to law enforcement and courts. It has been observed that ridge topography changes as latent prints age, including the widths of ridges that could be measured as a function of time. Crime suspects are commonly identified using fingerprint databases that contain reference inked tenprints (flat and rolled impressions). These can be of interest in aging studies as they provide baseline information relating to the original (nonaged) ridges’ widths. In practice, the age of latent fingerprints could be estimated following a comparison process between the evidentiary aged print and the corresponding reference inked print. The present article explores possible correlations between inked and fresh latent fingerprints deposited on different substrates and visualized with TiO₂. The results indicate that the ridge width of flat inked prints is most similar to fresh latent fingerprints_, and these should be used as the comparison standard for future aging studies.     

汗潜指印DNA提取方法的初步研究

目的建立渗透性载体及非渗透性载体上汗潜指印DNA的提取和检验方法。方法采用C-有-柱法及SiO2法两种DNA提取方法,PCR扩增后310型遗传分析仪检测。结果载玻片上3枚汗潜指印采用2种方法均可扩增出Amel及9个STR位点;纸上3枚汗潜指印用SiO2法检见Amel及9个STR位点,而用C-有-柱法检验结果不稳定。渗透性及非渗透性载体上1及2枚汗潜指印,采用上述两种DNA提取方法,检验结果均不稳定。结论所建立的方法可以检见渗透性及非渗透性载体上汗潜指印DNA,并达到同一认定的程度。