Author Abstracts: Tuesday, Sept. 20
Abstracts are listed in order of author presentations. Abstracts and the presentation schedule are subject to change; check this page regularly for additions and updates.
Microtomy of Pigmented Fibers: Making the Right Cut
Ethan Groves (presenting author), Kelly Brinsko Beckert, Otyllia Abraham, Christopher S. Palenik — Microtrace LLC
The number, color, particle size, morphology, density, and ultimately, the identity of the pigments in solution-dyed fibers remains an underexploited characteristic of forensic fiber examinations. Traditional microscopical examination of fibers as whole mounts presents challenges to the detailed study of individual pigments, which can be orders of magnitude smaller than the diameter of the fiber. Therefore, to maximize the amount of pigment information obtained from a solution-dyed fiber, proper sample preparation is required.
Microtomy of solution-dyed fibers to generate thin cross-sections has been extremely helpful to visualize and characterize individual pigments and pigment agglomerates within a fiber. The fine diameter and soft polymeric nature of solution-dyed textile fibers requires that they be embedded in a medium to facilitate sectioning. Evaluation of embedding media, section thickness, and sectioning parameters have been conducted to obtain suitable sections from various fiber types for examination by oil immersion, fluorescence, and transmission electron microscopy. Examples of the challenges encountered, solutions postured, and a glimpse into the range of data obtained will be presented.
The Application of Electron Backscatter Diffraction to Forensic Evidence Traces
Tiffany Millett and Thomas A. Kubic (presenting author) — John Jay College of Criminal Justice and the Graduate Center, CUNY
There are few reported applications of electron backscatter diffraction (EBSD) to forensic science problems in the literature. One application of EBSD is in firearm serial number restoration as a complementary technique to the time-consuming and tedious chemical etching methods. Kikuchi lines are patterns of electrons formed by scattering (due to Bragg’s law of diffraction) and electron backscattered electrons have been known for a long time and have been extensively employed in the production of ultra-high purity silicon used in computer chip manufacture to confirm the crystal structure of the surface employed. Historically, the solution of the necessary equations was difficult and time consuming. With the availability of high-speed, high memory capacity computers, concomitant with high-resolution digital cameras for recording EBSD images, this technique will lend itself to more applications in the analysis of evidence traces.
We will present the result of our research to expand the use of EBSD and describe its application to the identity of a number of materials that are important in the forensic analysis of trace evidence, including mineral grains, polymorphs, and gem stones.
Some Thoughts and Observations on Inscriptions Encountered in Antiquarian Books on Microscopy and Microchemistry
Skip Palenik — Microtrace LLC
In the course of studying original and early editions of books devoted to analytical microscopy and microchemistry, which I have acquired over the years, I have gradually developed a keen interest not only in their texts, illustrations, and bindings but also in certain embellishments in the form of inscriptions that that are, on occasion, to be found in some of them. This presentation will illustrate and provide background information about some of the most interesting (and some personal) of those in my collection. They consist of autographs, notes of presentation as gifts to persons and institutions, textual comments, institutional stamps, etc. They provide, I believe, not only some degree of enjoyment and scholarly entertainment but also fascinating insights into otherwise unknowable details about the authors and their books that are otherwise lost to history.
What Colors Do You Have for Your Michel-Lévy Chart?
Andrew A. “Tony” Havics — pH2, LLC
The Michel-Lévy Chart of Birefringences has been a staple for the light microscopist since its inception in 1888. There have been many charts produced with many variations of color. The displayed color scheme depends on the distribution from the light source, the eye of the receiver, and the wavelength selected for “red.” Even attempts to create a chart by first principles reveals that variation is inevitable. The author will rethink the precision of birefringence after exploring the chart of many colors.
Forensic Microscopy of Pigmented Fibers
Kelly Brinsko Beckert (presenting author), Otyllia Abraham, Ethan Groves, Christopher S. Palenik — Microtrace LLC
Fibers are one of the most common types of trace evidence encountered, and color is a primary feature of nearly every fiber comparison. Color is utilized at nearly every stage of analysis: from the initial search for target fibers and initial microscopical comparison of questioned and known samples, to late-stage objective comparisons by microspectrophotometry (MSP). In contrast to dyed fibers (i.e., solution dyed fibers), pigmented fibers are colored by the addition of insoluble pigment to the liquid polymer prior to extrusion. Such fibers are becoming increasingly common due to a variety of factors, including their ability to withstand harsh cleaning agents, inherent resistance to fading, and environmentally-friendly manufacturing methods. The number of pigment types, their identity, particle size, and density of pigmentation represent unexploited properties that can be used to evaluate fiber associations or provide investigative information during a fiber analysis. However, there have been no systematic studies of pigmented fibers; and therefore, no practical guidance is available to the bench-level analyst to identify, characterize, or interpret pigmented fiber evidence in forensic fiber cases.
This research fills this knowledge gap through a systematic study of pigmented fibers. The selected fiber samples span major manufacturers, include various applications of pigmented fibers, and represent the variety of colors and polymers that are produced. This presentation will provide an overview of results arising from the critical study of samples from this population of pigmented fibers by polarized light, oil immersion, and fluorescence microscopy. This study of fibers is supported by research into sample preparation techniques, including longitudinal whole mounts and cross sections, that have been optimized to maximize the resolution of individual pigment particles that often approach, or at times exceed (are smaller than) the resolution limits afforded by light microscopy. The range of information that has been obtained and tabulated from these samples includes methods of recognizing pigmented fibers, estimates of the number of different pigment types present in a fiber, and tabulations of the color, size, and morphology of individual pigment grains detected in a given sample.
Adapting to the Times: A Look at Online Microscopy Course Instruction
Sebastian Sparenga — McCrone Research Institute
With the arrival of the pandemic in 2020, in-person meetings and other social interactions came to an abrupt halt. This forced a transition to online conferencing via numerous video-based meeting platforms, which became the new normal for conducting everything from work meetings and instructional courses to social gatherings and group gaming — an effective way to communicate safely with each other. McCrone Research Institute initially held several “online learning sessions,” which attracted great interest, and then took the initiative to offer several live microscopy courses on Zoom. Two years later, the Institute continues to teach part of its curriculum online, with much success. This talk will discuss the transition from in-person learning to live online instruction for several types of microscopy topics.
Applications of Microanalysis to Identifying and Sourcing Particle Contaminants: Particle Identification in an IV Bag
Katie M. White (presenting author) and Skip Palenik — Microtrace LLC
In addition to materials identification, foreign matter analysis often includes a determination of potential sources for the identified contaminant. This is especially important to industrial clients conducting root-cause investigations, who aim to prevent future contamination from occurring in their processes.
In this case study, IV bags containing solutions with unknown particles were submitted for identification and comparison to previously analyzed samples. This presentation will illustrate the ways in which polarized light microscopy, coupled with a broad range of microanalytical methods, can provide analytical information that goes beyond the identity of a particle towards assisting a client with constraining its source. Methods that included Fourier-transform infrared microspectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and thermal microscopy each contributed to the solution of particle identity and source.
A Comparative Study on the Background Presence of Glass and Paint in Various Populations and Seasons in the U.S.
Andra Lewis1 (presenting author), Lauryn Alexander2, Patrick Buzzini1, and Tatiana Trejos2 — 1Department of Forensic Science, Sam Houston State University, 2Department of Forensic and Investigative Sciences, West Virginia University
Glass and paint particles are often recovered from crime scenes. The chance presence of these traces in the population contributes to evaluating their evidential value. A collaborative study was conducted to search for glass and paint particles using tape liftings from volunteers with different demographics and socioeconomic backgrounds in different U.S. cities during various seasons. The study aimed at producing information on the chance of randomly finding these particles in individuals not connected with criminal activities. Sampling was conducted in Morgantown, WV (winter and summer), Pittsburgh, PA (summer), Huntsville, TX (spring), and Houston, TX (summer).
Beyond what the Eye Can See: Application of Long-Exposure Fluorescence Imaging to the Characterization of Pigmented Fibers
Otyllia Abraham (presenting author), Kelly Brinsko Beckert, Ethan Groves, Christopher S. Palenik — Microtrace LLC
Fibers represent one of the largest categories of trace evidence. Forensic fiber examination is generally used to facilitate comparisons between questioned, evidentiary fibers and known sources, during which color plays a vital role. Historically, pigmented fibers (i.e., solution dyed fibers) have represented a small percentage of the colored fiber market. In recent years, however, pigmented fibers have increased in popularity due to the reproducibility and lightfastness of the pigments when compared to dyed fibers. Despite the increased application of pigmented fibers, systematic studies regarding the microscopical examination of these fibers have not been completed.
This presentation explores the complementary role that polarized light microscopy and fluorescence microscopy can play in the examination, characterization, and interpretation of pigmented fiber evidence. Traditional fluorescence microscopy is generally performed on whole fibers, which gives information related to the gross fluorescence of the fiber. This fluorescence can arise from the inherent fluorescence of the polymer, the presence of an optical brightener, or the fluorescing colorants within the fiber. In this work, both whole mounts and transverse thin cross-sections of fibers were prepared from a curated collection of pigmented fibers spanning a range of polymers, colorants, manufacturers, and commercial applications. These preparations have been examined by a combination of white light and fluorescence microscopy, and the results illustrate that with proper sample preparation, individual pigment particles can be visualized and, in many instances, different pigments within a single fiber may be observed. With a sufficiently thin fiber and a modern digital camera with built-in image stabilization, relatively long-exposure fluorescence imaging (up to 30-second exposures) can provide substantial additional information beyond that which is readily observable by visual examination through the microscope ocular alone. This talk will discuss necessary considerations for long-exposure fluorescence imaging and will provide examples of further information that can be gleaned from fluorescence microscopy of pigmented fibers.
A New Method for Enhanced Fluorescence Detection and Discrimination
Charles Mazel — NIGHTSEA
A new method has been developed that can enhance detection and discrimination of fluorescent features. The method is intended for situations in which recognition of a fluorescence of interest may be hindered by the presence of other sources of fluorescence within the field of view, whether arising from the background or from other features. The problem can arise when the excitation light source needed to excite the fluorescence of the desired target also excites fluorescence of these other features, creating loss of contrast or distraction.
In its simplest form, the method uses two excitation light sources selected to exploit differences in excitation spectra between the fluorescence of interest and the extraneous fluorescence. The sources are driven in an alternating pattern and their intensity is adjusted to create a condition in which the extraneous fluorescence appears at an approximately constant intensity throughout the pattern, while the intensity of the fluorescence of interest changes, creating a blinking effect. This blinking effect preferentially draws attention to the fluorescence of interest for visual detection by a human, and it is also amenable to optical detection by an electronic system for automated processing. The method is currently being refined and applications are being explored.
Reflected Light and Scanning Electron Microscopy Applications to a Writing Sequence: A Case Study
Patricia Fisher and Joseph G. Barabe1 (presenting author) — 1Barabe & Associates LLC
The contested word “dowry” only overlapped with the word “cheque” in one small location of an original signed document. The downstroke of the “y” in dowry overlapped with the “u” in cheque. One party said that the word was part of the document, the other argued that it was added afterwards. The document examiner contracted to resolve this issue contacted the presenter, as I had published a research report on this issue with co-authors Wayne Niemeyer, Senior Research Scientist at McCrone Associates, and Vickie Willard, Forensic Document Examiner. Before accepting the assignment, the author (Barabe) refused to accept any background information that would bias his findings in either direction, and especially, the writing sequence desired by the client.
The writing overlap was examined with stereomicroscopes without resolving the issue, but examination with a darkfield reflected-light polarized light microscope and deep-focus photomicrography with Helicon’s focus-stacking software. The client also asked for scanning electron microscopy (SEM) examination as well; this was performed by a third party using the protocol developed by Mr. Niemeyer. The conclusions reached by both darkfield reflected-light microscopy and SEM coincided. In conclusion, we found that both microscopical techniques provided positive results, and using both methods provided strong confirmation.
Scanning White Light Interferometry: Creating a More Complete Picture
Kevin Brady — Tredegar Surface Protection LLC
Careful measurement of particle dimensions is common and critical to identification of unknowns. Typically, light microscopists describe two-dimensional size: length, width, diameter, aspect ratio, etc. Scanning White Light Interferometers (SWLI) allow us to add a third dimension and measure at vertical (z-direction) resolutions in nanometers or greater. While the technical aspects of the SWLI are impressive, the beauty of the images created can be inspiring as well. Some three-dimensional images will be presented and discussed.