Williams Mazzella

Differentiation of Blue Ballpoint Pen Inks by Laser Desorption Ionization Mass Spectrometry and High‐Performance Thin‐Layer Chromatography

ABSTRACT: The differentiation of inks on a questioned document can highlight a fraudulent insertion and is usually carried out by optical comparison and thin‐layer chromatography (TLC). Laser desorption ionization mass spectrometry (LDI‐MS) may also be used for the analysis of dyes from ink. This analytical technique was compared with a standard method of high‐performance TLC (HPTLC) according to their capacity to differentiate blue ballpoint inks. Ink entries on paper from 31 blue ballpoint pens have been analyzed and their dye ink formulations compared. The pens were classified into 26 classes by LDI‐MS against 18 for HPTLC. LDI‐MS proved to be a more powerful method for differentiating ink formulations because it provides information about dye structures (molecular weights) and relative quantification of dye classes (peak areas). Sample preparation was minimal and analysis time was short in contrast to the more complex extraction, application, and development steps of the HPTLC method. However, only basic dyes and pigments were identified using positive mode LDI‐MS, while HPTLC did yield additional information about acid dyes.

Classification and Identification of Photocopying Toners by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS): I. Preliminary Results

A diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique has been employed to record the IR spectra of 152 different black and color toners used in photocopiers and laser printers. Based on characteristic absorption bands in the infrared (IR) spectra, 149 of these toners were classified into 36 distinct groups. A small sample of toner was removed from the surface of a questioned document (produced on a photocopier or laser printer), the IR spectrum was recorded using the diffuse reflectance technique, and the class of toner was determined by comparison with a collection of standard spectra. A knowledge of the compatibility of each type of toner can then be employed to provide a list of photocopying machines (or laser printers) that could have produced the questioned document. The technique does not appear to be affected by the age of the photocopy, the batch or toner, or the prior treatment of the questioned document with a fingerprint development reagent such as ninhydrin.

A New Europium Chelate as a Fluorescent Dye for Cyanoacrylate Pretreated Fingerprints—EuTTAPhen: Europium ThenoylTrifluoroAcetone Ortho-Phenanthroline

The use of luminescent dyes to enhance fingerprints developed with cyanoacrylate is now a well established procedure in most fingerprint laboratories. Misner, Wilkinson and Watkin [1] have proposed a new fluorescent dye using an Europium complex (TEC). The purpose of the present paper is to report on further studies of this dye (TEC) and some analogues. Preliminary tests on cyanoacrylate pretreated fingerprints showed that a formulation of EuTTAPhen (Europium ThenoylTrifluoroAcetone ortho-phenanthroline) was the most efficient complex giving the best luminescence intensity of the treated fingerprints, a Stokes shift of 262 nm and reduced practical drawbacks.

Statistical discrimination of black gel pen inks analysed by laser desorption/ionization mass spectrometry.

Pearson correlation coefficients were applied for the objective comparison of 30 black gel pen inks analysed by laser desorption ionization mass spectrometry (LDI-MS). The mass spectra were obtained for ink lines directly on paper using positive and negative ion modes at several laser intensities. This methodology has the advantage of taking into account the reproducibility of the results as well as the variability between spectra of different pens. A differentiation threshold could thus be selected in order to avoid the risk of false differentiation. Combining results from positive and negative mode yielded a discriminating power up to 85%, which was better than the one obtained previously with other optical comparison methodologies. The technique also allowed discriminating between pens from the same brand.

STUDIES OF TECHNIQUES FOR ANALYSIS OF PHOTOCOPY TONERS BY IR

A study was undertaken to examine three measurement techniques for the analysis of photocopy toners by microscopical infrared spectrometry (IR) and to compare these techniques to studies previously done by Diffuse Reflectance (DR). Based on our preliminary studies, analysis of photocopy toners may be successfully performed by DR, microscopical Attenuated Total Reflectance (ATR) with a germanium Internal Reflection Element (IRE) or by microscopical Reflection-Absorption (R-A) techniques with a variety of reflecting media including mirrored slides, low emissivity glass, and aluminum foil. Selection of the analysis technique can be made based on equipment availability, budgetary constraints, ease of sample preparation, speed of analysis, and importance of the original photocopied document to determine if a mildly destructive technique can be used.

A simple combined technique for the analysis of toners and adhesives

A simple but efficient procedure has been developed for the extraction and analysis of adhesives and toners on questioned documents. From the single extraction of a sample of document equivalent to approximately 1 cm of a printed line, it is possible to record both the infrared spectrum and the pyrogram of the compound of interest. Good sensitivity and reproducibility has been observed for the analysis of toner and adhesive samples and the technique has proved effective in actual casework. The application of the technique to the analysis of adhesive tapes, inks and correction fluids is under investigation.

Discussion on how to implement a verbal scale in a forensic laboratory: Benefits, pitfalls and suggestions to avoid misunderstandings

In a recently published guideline for evaluative reporting in forensic science, the European Network of Forensic Science Institutes (ENFSI) recommended the use of the likelihood ratio for the measurement of the value of forensic results. As a device to communicate the probative value of the results, the ENFSI guideline mentions the possibility to define and use a verbal scale, which should be unified within a forensic institution. This paper summarizes discussions held between scientists of our institution to develop and implement such a verbal scale. It intends to contribute to general discussions likely to be faced by any forensic institution that engages in continuous monitoring and improving of their evaluation and reporting format. We first present published arguments in favour of the use of such verbal qualifiers. We emphasise that verbal qualifiers do not replace the use of numbers to evaluate forensic findings, but are useful to communicate the probative value, since the weight of evidence in terms of likelihood ratio are still apprehended with difficulty by both the forensic scientists, especially in the absence of hard data, and the recipient of information. We further present arguments that support the development of the verbal scale that we propose. Recognising the limits of the use of such a verbal scale, we then discuss its disadvantages: it may lead to the spurious view according to which the value of the observations made in a given case is relative to other cases. Verbal qualifiers are also prone to misunderstandings and cannot be coherently combined with other evidence. We therefore recommend not using the verbal qualifier alone in a written statement. While scientists should only report on the probability of the findings - and not on the probability of the propositions, which are the duty of the Court - we suggest showing examples to let the recipient of information understand how the scientific evidence affects the probabilities of the propositions. To avoid misunderstandings, we also advise to mention in the statement what the results do not mean. Finally, we are of the opinion that if experts were able to coherently articulate numbers, and if recipients of information could properly handle such numbers, then verbal qualifiers could be abandoned completely. At that time, numerical expressions of probative value will be appropriately understood, as other numerical measures that most of us understand without the need of any further explanation, such as expressions for length or temperature.

Examination of heterogeneous crossing sequences between toner and rollerball pen strokes by digital microscopy and 3-D laser profilometry.

Abstract:  The determination of line crossing sequences between rollerball pens and laser printers presents difficulties that may not be overcome using traditional techniques. This research aimed to study the potential of digital microscopy and 3‐D laser profilometry to determine line crossing sequences between a toner and an aqueous ink line. Different paper types, rollerball pens, and writing pressure were tested. Correct opinions of the sequence were given for all case scenarios, using both techniques. When the toner was printed before the ink, a light reflection was observed in all crossing specimens, while this was never observed in the other sequence types. The 3‐D laser profilometry, more time‐consuming, presented the main advantage of providing quantitative results. The findings confirm the potential of the 3‐D laser profilometry and demonstrate the efficiency of digital microscopy as a new technique for determining the sequence of line crossings involving rollerball pen ink and toner.

A simple logical approach to questioned envelopes examination

This case report outlines research undertaken as the result of a document examination case in which two envelopes were involved. The combination of the circumstances of the case and the results of the examination allows a simple application of a logical approach to pre-assess the probability that an envelope (or a package) potentially recovered at a suspects home comes from the same batch (same source) as questioned envelopes. This highlights that it is useful to examine envelopes.

Use of a Silicon Carbide Sampling Accessory for the Diffuse Reflectance Infrared Fourier Transform Analysis of Samples of Interest to Forensic Science

An infrared spectroscopy method is described which requires little sample preparation and may be used for analysis of a wide range of samples of interest to forensic science. A small quantity of a sample is rubbed onto an abrasive silicon carbide disk, which is then measured by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The technique has been successfully applied to the infrared analysis of paint, synthetic rubber, cosmetics, corrector fluid, and adhesives.