Confocal Raman imaging and chemometrics applied to solve forensic document examination involving crossed lines and obliteration cases by a depth profiling study

This article describes a non-destructive analytical method developed to solve forensic document examination problems involving crossed lines and obliteration.

Near infrared hyperspectral imaging for forensic analysis of document forgery

Hyperspectral images in the near infrared range (HSI-NIR) were evaluated as a nondestructive method to detect fraud in documents. Three different types of typical forgeries were simulated by (a) obliterating text, (b) adding text and (c) approaching the crossing lines problem. The simulated samples were imaged in the range of 928-2524 nm with spectral and spatial resolutions of 6.3 nm and 10 μm, respectively. After data pre-processing, different chemometric techniques were evaluated for each type of forgery. Principal component analysis (PCA) was performed to elucidate the first two types of adulteration, (a) and (b). Moreover, Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used in an attempt to improve the results of the type (a) obliteration and type (b) adding text problems. Finally, MCR-ALS and Partial Least Squares-Discriminant Analysis (PLS-DA), employed as a variable selection tool, were used to study the type (c) forgeries, i.e. crossing lines problem. Type (a) forgeries (obliterating text) were successfully identified in 43% of the samples using both the chemometric methods (PCA and MCR-ALS). Type (b) forgeries (adding text) were successfully identified in 82% of the samples using both the methods (PCA and MCR-ALS). Finally, type (c) forgeries (crossing lines) were successfully identified in 85% of the samples. The results demonstrate the potential of HSI-NIR associated with chemometric tools to support document forgery identification.

Validation of LAB color mode as a nondestructive method to differentiate black ballpoint pen inks

Nondestructive digital processing methods such as lab color mode (available in Adobe Photoshop) are emerging as alternative methods for forensic document examiners to use when attempting to differentiate writing instrument inks. Although these techniques appear to be viable, little data currently exists regarding the known or potential error rates associated with these techniques. Without adequate data, the validity and reliability of these techniques, including lab color, can not be established. In an attempt to begin to address these issues, 44 black ballpoint ink pens were obtained and used to create 990 pen-pair samples for analysis using established lab color mode techniques. No erroneous findings of "different" were reported following the examination of the known pen-pair combinations in which the same pen was used to create the samples (n = 44). Of the remaining 946 samples, 737 pen-pair samples were differentiated using the lab color mode method, while 209 samples were unable to be differentiated and were recorded as either being "similar" (n = 153) or "unsure" (n = 56). Comparison of the lab color mode results with the results obtained through additional testing using traditional infrared reflectance and infrared luminescence test methods showed that lab color differentiated 102 pen-pair samples (11%; 102/946) that were not differentiated using a VSC-4C.

Diary of an Astronaut: Examination of the Remains of the Late Israeli Astronaut Colonel Ilan Ramon's Crew Notebook Recovered After the Loss of NASA's Space Shuttle Columbia

Two months after the fatal re-entering into the Earth's atmosphere of Columbia flight STS-107, the remains of Israeli astronaut Colonel Ilan Ramon's Crew Notebook were found strewn in a field in San Augustine County, TX. The random pile of papers was found to have survived the calamity of the Shuttle's disintegration remarkably well. Most of the papers recovered were torn and/or washed out to varying degrees but only mildly charred around the edges. The sheets of paper could be categorized into four groups: Group I: eight sides of paper written while in space in black ink and in pencil--Ramon's personal diary; the writing on these eight sides of paper survived well and is only missing where the pages were torn. Small fragments found in the field were physically matched to holes in the pages thus locating their original positions in the text. Group II: six sides of technical preparation notes written by Ramon before the mission. The writing on these pages was washed out entirely, but much of it was visualized using infrared luminescence. Group III: eight sides of personal notes prepared by Ramon before the mission written in blue ink. The writing on these pages was barely visible to the naked eye and not visualized by infrared luminescence, but was made largely legible by digital enhancement imaging. Group IV: a few sides of printed technical information. These pages were mostly intact and were not examined at length as they contained standard printed material. After completion of examinations at the Questioned Document Laboratory of the Israel Police, the diary was transferred to the Paper Conservation Department of the Israel Museum for preservation and strengthening treatments.

Color Separation in Forensic Image Processing

In forensic image processing, it is often important to be able to separate a feature from an interfering background or foreground, or to demonstrate colors within an image to be different from each other. In this study, a color deconvolution algorithm that could accomplish this task is described, and it is applied to color separation problems in document and fingerprint examination. Subtle color differences (sometimes invisible to the naked eye) are found to be sufficient, which is demonstrated successfully for several cases where color differences were shown to exist, or where colors were removed from the foreground or background. The software is available for free in the form of an Adobe Photoshop-compatible plug-in.