Leading Edge Techniques in Forensic Trace Evidence Analysis E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 586

Veröffentlichungsjahr: 2022

Beschreibung

Leading Edge Techniques in Forensic Trace Evidence Analysis In-depth exploration of the latest methodologies, tools, and techniques for analyzing trace evidence In Leading Edge Techniques in Forensic Trace Evidence Analysis, distinguished and highly qualified contributors cover the significant advances in methodology and instruments that are now being used to analyze trace evidence in forensic laboratories, including new techniques used to determine authenticity of objects and artifacts (such as Combined Raman/LIBS Microscopy) and those used to analyze surface treatments (such as py-GC-PARCI-MS). The work also covers new evidence types, such as surface-modified fibers, microscopic particles, and shimmer, and provides detailed explanations and practical examples of all of the aforementioned topics. Among the topics covered are: * Forensic analysis of shimmer particles in cosmetics samples, glitter and other flake pigments, and x-ray photoelectron spectroscopy * Surface acoustic wave nebulization mass spectrometry, forensic applications of gas chromatography vacuum ultraviolet, and spectroscopy paired with mass spectrometry * Density determination and separation via magneto-Archimedes levitation and elemental imaging of forensic traces with macro and micro XRF * Characterization of human head hairs via proteomics and Raman and surface-enriched Raman scattering (SERS) for trace analysis With detailed explanations of modern methodologies, tools, techniques, and evidence types in trace evidence forensics, along with helpful guidance to put covered concepts into practice, Leading Edge Techniques in Forensic Trace Evidence Analysis serves as an invaluable hands-on reference for scientists in forensic laboratories worldwide.

Leseprobe

Table of Contents

Cover

Series Page

Title Page

Copyright

List of Contributors

Foreword

Preface

1 Forensic Analysis of Shimmer Particles in Cosmetic Samples

1.1 Introduction

1.2 What is Shimmer?

1.3 Shimmer Detection and Collection

1.4 Analysis of Shimmer Particles

1.5 Ideal Contact Trace

1.6 Case Examples

1.7 Conclusion

Acknowledgments

References

2 Glitter and Other Flake Pigments

2.1 Introduction

2.2 Glitter Update

2.3 Cutting Film into Individual Glitter Particles

2.4 Reflectance

2.5 Embossed Effects

2.6 Color

2.7 Specific Gravity

2.8 Is It Glitter or a Flake Pigment?

2.9 Materials and Processes that Have Been Used to Produce Flake Materials

References

3 X‐ray Photoelectron Spectroscopy

3.1 Introduction

3.2 Background and Theory

3.3 Instrumentation

3.4 Argon‐Ion Cluster Beam Technology

3.5 Evidence Type Examples

3.6 Future Directions of XPS and Forensics

3.7 Conclusions

Acknowledgements

References

4 Density Determination and Separation via Magnetic Levitation

4.1 Introduction

4.2 Objectives of the Work

4.3 Guidance to the Reader

4.4 Theoretical Basis*

4.5 Preparation for Density Determination Via MAGLEV

4.6 Protocols for Measurement of Density, and Separation Using MAGLEV

4.7 Trace‐Evidence‐Like Materials That Have Been Analyzed with MAGLEV

4.8 Instructions for the Construction of MAGLEV Devices

4.9 Conclusion

References

5 Forensic Applications of Gas Chromatography – Vacuum Ultraviolet Spectroscopy Paired with Mass Spectrometry

5.1 Introduction

5.2 Background of Mass Spectrometry

5.3 Background of Vacuum Ultraviolet Spectroscopy

5.4 Combining GC/VUV and GC/MS

5.5 Analysis of Fentanyl Analogues

5.6 Analysis of Smokeless Powders

5.7 Analysis of Lipstick

5.8 Analysis of Blood Alcohol Content and Inhalants

5.9 Analysis of Fire Debris Samples

5.10 Conclusion

References

6 Surface Acoustic Wave Nebulization‐Mass Spectrometry

6.1 Theory and Instrumentation

6.2 Analysis of Complex Samples

References

7 Elemental Imaging of Forensic Traces with Macro‐ and Micro‐XRF

7.1 Introduction

7.2 XRF Imaging Methods and Instrumentation

7.3 Elemental Imaging of Gun Shot Residues

7.4 Using Elemental Markers to Detect and Image Biological Traces

7.5 Visualizing Cosmetic and Personal Care Product Stains

7.6 Noninvasive Imaging of Hidden and Concealed Forensic Traces

7.7 Future Outlook

Acknowledgments

References

8 Characterization of Human Head Hairs via Proteomics

8.1 Introduction

8.2 Human Hair

8.3 Human Hair as Forensic Evidence: The Investigative Value of Hair

8.4 Current and Emerging Proteomic Methods for Forensic Human Hair Analysis

8.5 Current and Emerging Methods for Forensic Human Hair Analysis

8.6 Challenges to Implementing Protein Sequencing in Forensic Casework

8.7 Conclusion

Acknowledgments

References

9 Photo‐induced Force Microscopy

9.1 Introduction

9.2 Working Principle and Instrumentation

9.3 Trace Evidence Examples

References

10 Raman and Surface‐Enhanced Raman Scattering (SERS) for Trace Analysis

10.1 Introduction

10.2 Theory

10.3 Instrumentation

10.4 Forensic Applications

References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 Microscopic size measurements obtained for Red Wine CP‐504 (natura...

Chapter 2

Table 2.1 Example of composition of biodegradable glitter.

Chapter 3

Table 3.1 Table showing atomic concentration of plain and coated fiber.

Table 3.2 Chart showing elemental composition of several hair chalks availab...

Table 3.3 Chart showing surface atomic concentration from three separate man...

Table 3.4 Frequently used anode materials for XPS and their associated energ...

Chapter 4

Table 4.1 The cost of the most common paramagnetic compounds used for MAGLEV...

Table 4.2 Substances relevant to forensics that have been levitated with MAG...

Table 4.3 Specifications for the NdFeB magnets used in MAGLEV devices.

Chapter 5

Table 5.1 Determination coefficients and limits of detection for each fentan...

Table 5.2 Quantification results of ethanol and BAC/inhalant compounds.

Chapter 7

Table 7.1 Reported average elemental levels in human biological fluids (in b...

Table 7.2 Elements detected in personal care and cosmetic products with micr...

Chapter 9

Table 9.1 Comparison of near‐field infrared optical techniques.

Chapter 10

Table 10.1 Most common lasers used in Raman spectroscopy.

Table 10.2 Typical laser spot size for Raman measurements using the most com...

List of Illustrations

Chapter 1

Figure 1.1 Shimmer thin film light interference based on the concept of a Fa...

Figure 1.2 Microscopic images of (a and b) Red Wine CP‐504 in reflectance an...

Figure 1.3 Microscopic images of (a) Red Wine CP‐504 and (b) Superstar Red W...

Figure 1.4 Overlay of FTIR spectra for (a) Ruby Red, Red Wine, Flash Red, an...

Figure 1.5 Raman spectra of white Claire's cosmetics lip gloss using the (a)...

Figure 1.6 Raman spectra of two different lip gloss samples from Clinique Gl...

Figure 1.7 Raman spectrum of Clarins Rouge Prodige lip gloss in the color Gr...

Figure 1.8 Overlay of XRD spectra for Red Wine and Superstar Red. Spectra sh...

Figure 1.9 Overlay XRD spectra for Ruby Red and Coral Reef. Spectra shown ar...

Figure 1.10 SEM secondary electron image of Lemon Yellow CP‐6013 shimmer sam...

Figure 1.11 Overlay of EDS spectra for (a) Red Wine and Superstar Red and (b...

Figure 1.12 Box plot representation of the intra‐ and inter‐sample variabili...

Figure 1.13 Comparison between the visible absorbance spectra of (a) questio...

Figure 1.14 EDS particle analysis of (a) control and (b) questioned lipstick...

Chapter 2

Figure 2.1 Two similar but different glitter particles viewed under polarize...

Figure 2.2 A schematic of rotary die cutting of glitter flakes (a) and laser...

Figure 2.3 Scanning electron micrographs of laser cut metallized polymer gli...

Figure 2.4 A schematic of a rotary drum cutter for producing glitter.

Figure 2.5 Specular and diffuse reflectance.

Figure 2.6 Long and thin flakes have a higher aspect ratio than thick flakes...

Figure 2.7 Options for metalizing and coating glitter.

Figure 2.8 Individual flakes sit on a surface at different angles as the eye...

Figure 2.9 The method of production of vacuum metallized flakes (VMF).

Figure 2.10 Example of Avery patented flake material, four layers to make fo...

Figure 2.11 Biaxial orientation using sequential stenter process showing how...

Figure 2.12 Polymer extrusion bubble process for simultaneous biaxial orient...

Figure 2.13 Layer doubling extrusion process to produce a multilayer thin fi...

Figure 2.14 Schematics of light reflection, scattering, and a combination of...

Figure 2.15 Spinning disc method of pigment flake production.

Figure 2.16 Fluidized bed process of coating flake pigments.

Figure 2.17 Ink jet technology for flake production.

Figure 2.18 Flake production options.

Chapter 3

Figure 3.1 Graph displaying number of papers published per year from 1991 to...

Figure 3.2 An example survey spectrum.

Figure 3.3 An example of a narrow region spectrum of a fluoropolymer.

Figure 3.4 Channeltron.

Figure 3.5 Non‐charge compensated spectrum (a) compared to the same sample a...

Figure 3.6 Diagram demonstrating charge compensation in XPS.

Figure 3.7 The cycle summary for XPS depth profiling.

Figure 3.8 Example depth profile of tantalum oxide on a tantalum substrate....

Figure 3.9 A single ion used for monatomic sputtering (a), and a cluster ion...

Figure 3.10 Chemical make‐up of PET.

Figure 3.11 An example of C1s spectra of a PET sample that has been sputtere...

Figure 3.12 Survey spectra comparison of a plain cotton fiber and a coated c...

Figure 3.13 Survey spectra comparing two coated cotton samples.

Figure 3.14 Carbon 1s spectra from two modified cotton samples. Coated 1 (a)...

Figure 3.15 Cluster depth profiles of Coated 1 (a) and Coated 2 (b) samples....

Figure 3.16 Depth profile of a low‐emissivity glass coating.

Figure 3.17 XPS depth profiles of self‐cleaning glass from Pilkington Activ ...

Figure 3.18 Monatomic depth profile of phone screen glass using 5 kV ions. (...

Figure 3.19 Cluster depth profile of phone glass screen using 20 kV clusters...

Figure 3.20 Comparison of sodium and potassium concentrations between monato...

Figure 3.21 Chemical composition cluster depth profile of hair without hair ...

Figure 3.22 XPS sample plate from a Thermo Scientific K‐Alpha with six examp...

Figure 3.23 XPS survey spectra of white hair chalk (a) and black hair chalk ...

Figure 3.24 Spectrum of gold using an aluminum anode (a) and a silver anode ...

Chapter 4

Figure 4.1 (a) The MAGLEV device consists of two permanent magnets at the to...

Figure 4.2 Schematics of four types of MAGLEV devices. The colored spheres r...

Figure 4.3 Magnetic field strength (see scale bars) at different positions a...

Figure 4.4 The levitation heights of glass‐bead density standards in various...

Figure 4.5 Calibration of MAGLEV devices using density standards. (a) Glass‐...

Figure 4.6 From calibration with density standards to density determination ...

Figure 4.7 Separation and extraction of powdered compounds using a HMFG MAGL...

Figure 4.8 Separation of bone from mineral using MAGLEV (LWD). (a) A fired b...

Figure 4.9 Separation of particles of glitter and gunpowder. (a) Light micro...

Figure 4.10 Time‐lapse images of the separation of mixtures of powdered drug...

Figure 4.11 Separation via MAGLEV and identification by FTIR‐ATR. (a) Image ...

Figure 4.12 Levitation and separation of glass from granular mixtures. (a) L...

Figure 4.13 Density determinations of polymers, metals, and air. (a) Levitat...

Figure 4.14 MAGLEV of cut pieces of human hair from the head and dandruff. (...

Figure 4.15 Schematics of the LWD, HMFG, and Axial MAGLEV devices viewed fro...

Chapter 5

Figure 5.1 Mass spectrum of butane and selected mass fragments. Source: Adap...

Figure 5.2 Diagram of the VUV Spectrometer developed by VUV Analytics, Inc. ...

Figure 5.3 VUV Analytics VGA‐100 spectrometer connected to a Thermo Scientif...

Figure 5.4 VUV absorption spectrum of hexane. Because hexane has only sigma ...

Figure 5.5 VUV absorption spectrum of 1‐hexene. Because a pi...

Figure 5.6 VUV absorption spectrum of benzene. Compounds containing more pi ...

Figure 5.7 TID analysis of a terpenes mixture. The chromatogram is divided i...

Figure 5.8 Example analysis with a coelution of

m

‐xylene/

p

‐xylene in a gasol...

Figure 5.9 Example analysis with a coelution of acetone/isopentane in a gaso...

Figure 5.10 Mass spectra of

m

‐xylene (a),

p

‐xylene (b), and

o

‐xylene (c), ad...

Figure 5.11 VUV absorption spectra of

m

‐xylene,

o

‐xylene, and

p

‐xylene. Desp...

Figure 5.12 Basic diagram of a GC/VUV/MS configuration using a column splitt...

Figure 5.13 Structures and mass spectra of crotonyl fentanyl (top) and cyclo...

Figure 5.14 VUV absorbance spectra of crotonyl fentanyl and cyclopropyl fent...

Figure 5.15 Twenty‐four fentanyl analogues characterized by Buchalter et al....

Figure 5.16 VUV spectra obtained for each set of positional isomers at conce...

Figure 5.17 Simultaneous cold EI MS (a) and VUV (b) detection for a mixture ...

Figure 5.18 A fully assembled cartridge compared to a disassembled cartridge...

Figure 5.19 A deconstructed IED using smokeless powder. Image provided by Dr...

Figure 5.20 VUV spectra and structures of additives found in smokeless powde...

Figure 5.21 VUV spectra of diphenylamine, 2‐nitrodiphenylamine, and 4‐nitrod...

Figure 5.22 Example analysis of a smokeless powder extract. Each additive co...

Figure 5.23 Simulated evidence containing traces of a cosmetic product. Whil...

Figure 5.24 Extract profile of one lipstick sample, along with the mass spec...

Figure 5.25 Extract profile of one lipstick sample at 125–430 nm. This filte...

Figure 5.26 Extract profile of one lipstick sample at 125–160 nm. Using this...

Figure 5.27 Extract profile of one lipstick sample at 170–205 nm. Using this...

Figure 5.28 Extract profile of one lipstick sample at 125–160 nm compared to...

Figure 5.29 Example chromatogram from the sample spi...

Figure 5.30 Spectral shapes of linear/branched alkanes (heptane), alkenes (1...

Figure 5.31 Spectral shapes of five aromatic compounds. While each compound ...

Figure 5.32 Profile of a gasoline sample analyzed by GC/VUV with selected pe...

Figure 5.33 Characterization of trace fuel extracted from a piece of fire de...

Chapter 6

Figure 6.1 (a) Schematic of the commercially available SAWN chip (LiNbO

3

), (...

Figure 6.2 The nebulization of a droplet on the SAWN chip taken with a five ...

Figure 6.3 The nebulization of a droplet on a SAWN chip and the subsequent i...

Figure 6.4 High‐speed microscopic images from nebulizing a water droplet on ...

Figure 6.5 Droplet size distribution of the SAWN including the larger drople...

Figure 6.6 Paper‐based SAWN–MS interface for direct analysis of blood sample...

Figure 6.7 SAWN‐MS spectrum of 1 μg/ml PETN diluted in Me...

Figure 6.8 SAWN‐MS spectrum of 30...

Figure 6.9 SAWN‐MS analysis of forensic case ex...

Figure 6.10 Flow diagram for fiber examination.

Figure 6.11 SAWN‐MS spectrum of wool fiber dyed with Acid Violet 7..

Figure 6.12 Analysis of a wool fiber dyed with Basic Violet 3 (C

25

H

30

ClN

3

) a...

Figure 6.13 The proposed mechanism for the production of Indigo from

E. coli

...

Figure 6.14 Comparison of cotton fibers dyed with a different type of Indigo...

Chapter 7

Figure 7.1 The relation between resolution, scan speed, and sensitivity in c...

Figure 7.2 The M4 micro‐XRF scanner from Bruker at the NFI (a) and the M6 MA...

Figure 7.3 XRF Cu image of the T‐shirt showing the location of the bullet ho...

Figure 7.4 Overlay of the XRF spectra for the three ammunition types. Data w...

Figure 7.5 Element‐specific images to illustrate how bullet holes can be mat...

Figure 7.6 Elemental hi‐res images of a specific area in the center of the T...

Figure 7.7 The effect of the shooting angle on the distribution pattern of g...

Figure 7.8 Element‐specific MA‐XRF images (Cu, Pb, Ba, and Sb) as a function...

Figure 7.9 Calibration curve for Zn on μ‐XRF...

Figure 7.10 M4 XRF signal for Zn as function of stain size as modeled by the...

Figure 7.11 MA XRF elemental scans of Fe (b), K (c), and Cl (d) and a combin...

Figure 7.12 MA XRF elemental scans of Zn (b), K (c), Cl (d), and Ca (e) of f...

Figure 7.13 XRF elemental scans of blood (a) and foundation make‐up (b) as m...

Figure 7.14 Amount of DNA quantified in extracts of sampled blood stains aft...

Figure 7.15 Photo of personal care sample grid on white cotton (a) and assoc...

Figure 7.16 XRF spectra of the three foundation products (a = Long lasting F...

Figure 7.17 Cosmetics applied to the mannequin prior to the smothering exper...

Figure 7.18 MA XRF elemental scans of Fe (b), Ti (c), K (d) Si (e), and S (f...

Figure 7.19 MA XRF elemental images of GSR (Pb (a), Ba (b), and Cu (c)) on a...

Chapter 8

Figure 8.1 Schematic representation of the structure and anatomy of human ha...

Figure 8.2 Basic structure of hair.

Figure 8.3 An overview of hair follicle cycling.

Figure 8.4 Schematic representation of the ultrastructure of a hair shaft. F...

Figure 8.5 Examples of anagen, catagen, and telogen phase hair roots. Exampl...

Figure 8.6 Concept of human hair comparison via proteomics – (a) wild type p...

Figure 8.7 Example of hair shaft keratin protein variants and associated nsS...

Figure 8.8 Example of STR loci and chromosomal locations. (a) STR loci typed...

Figure 8.9 nLC concentration effect.

Figure 8.10 The electrospray process.

Figure 8.11 Basic analysis scheme for parallel reaction monitoring.

Figure 8.12 Overview of bottom‐up proteomics with human hair sample processi...

Figure 8.13 nLC precolumn and analytical column with an ESI interface to a h...

Figure 8.14 Hybrid quadrupole‐Orbitrap Exploris mass spectrometer used in pr...

Figure 8.15 Automated instrument control software enables DDA for efficient ...

Figure 8.16 Analysis scheme for DIA using either an Orbitrap or a time‐of‐fl...

Figure 8.17 Schematic representation of a sheath‐liquid (a) and a sheathless...

Chapter 9

Figure 9.1 PiFM concept. The laser intensity is modulated at a frequency,

f

m

Figure 9.2 Comparison of PiF‐IR spectra (obtained on a single toner particle...

Figure 9.3 (a) Topography and PiFM images at (b) 1750 cm

−1

, (c) 1070 c...

Figure 9.4 Six PiF‐IR spectra from six locations on a single bare cotton kni...

Figure 9.5 Six PiF‐IR spectra from six locations on a single cotton fiber co...

Figure 9.6 Comparison of the averaged PiF‐IR spectra for bare cotton (labele...

Figure 9.7 Comparison between a spectrum from a bare cotton woven fiber (B2)...

Figure 9.8 Comparison between a spectrum from a bare cotton woven fiber (B2)...

Figure 9.9 Comparison of spectra from single fibers that are coated with 3M ...

Figure 9.10 Two PiFM images at 1048 and 1241 cm

−1

show the location of...

Figure 9.11 Comparison of a PiF‐IR spectrum associated with a bare fiber (C2...

Figure 9.12 Comparison of PiF‐IR spectra from C2 (bare) and C1 (coating A) f...

Figure 9.13 Comparison of PiF‐IR spectra from C2 (bare) and C3 (coating B) f...

Figure 9.14 Comparison of the spectra from A1 (cotton knit fiber) and B1 (co...

Figure 9.15 Comparison of the spectra from B3 (cotton woven fiber) with the ...

Figure 9.16 Optical views of the glitter and shimmer samples with general ar...

Figure 9.17 Comparison of PiF‐IR spectra (bottom panel) to the measured ATR‐...

Figure 9.18 Comparison of PiF‐IR spectra (bottom panel) to the measured ATR‐...

Figure 9.19 Comparison of PiF‐IR spectra (bottom panel) to the measured ATR‐...

Figure 9.20 Comparison of PiF‐IR spectra (bottom panel) to the measured ATR‐...

Figure 9.21 Topography and PiFM (at 1550 cm

−1

) images at the same loca...

Chapter 10

Figure 10.1 Schematic illustration of Rayleigh, Stokes, and anti‐Stokes scat...

Figure 10.2 Schematic illustration of the Raman scattering over wavelength (...

Figure 10.3 Schematic illustration of the surface‐enhanced Raman spectroscop...

Figure 10.4 (a) Noble metals such as silver or gold act as antennas and loca...

Figure 10.5 Standard Raman (blue) and SERS (black) spectra of the dye Basic ...

Figure 10.6 Most common type of SERS substrates that are of interest in fore...

Figure 10.7 Basic components of a benchtop micro‐Raman spectrometer.

Figure 10.8 Small pieces of Agarose gel can be put in contact with ink entri...

Figure 10.9 Schematic procedure of the extraction of non‐mordant dyes from f...

Guide

Cover Page

Table of Contents

Series Page

Title Page

Copyright

List of Contributors

Foreword

Preface

Begin Reading

Index

End User License Agreement

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Cover photos from

On the book's front cover, the left photo shows a Vacuum Metal Deposition (VMD) instrument with a technician removing a test sample showing VMD-developed fingermarks. The right photo shows the handprint that was developed on cloth cut from a pillow case.

Although a simulation, the photo depicts a palm print on a pillow case developed at West Technology Forensics using vacuum metal deposition. The bottom right photo on this page was also developed on a pillow case by VMD. Do you see the impres sion of a nose?

Photo illustrations created by West Technology Forensics (https://www.westtechnology.co.uk/forensic/) and used with permission.

Think of how often a nurse, caregiver, or family member falls under suspicion when a patient dies under uncertain circumstances. Vacuum metal deposition on the pillow might tend to exonerate all as far as death by smothering, or it might actually show the means of death and who did it

Leading Edge Techniques in Forensic Trace Evidence Analysis

More New Trace Analysis Methods

Edited byRobert D. Blackledge

This edition first published 2023

© 2023 John Wiley & Sons, Inc.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.

The right of Robert D. Blackledge to be identified as the author of this work has been asserted in accordance with law.

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Library of Congress Cataloging‐in‐Publication Data

Names: Blackledge, Robert D., editor.

Title: Leading edge techniques in forensic trace evidence analysis : more

     new trace analysis methods / edited by Robert D. Blackledge.

Description: First edition. | Hoboken, NJ : Wiley, 2023.

Identifiers: LCCN 2022025481 (print) | LCCN 2022025482 (ebook) | ISBN

     9781119591610 (cloth) | ISBN 9781119591832 (adobe pdf) | ISBN

     9781119591801 (epub)

Subjects: LCSH: Trace evidence–Analysis.

Classification: LCC HV8073 .L33495 2023 (print) | LCC HV8073 (ebook) |

     DDC 363.25/6–dc23/eng/20220714

LC record available at https://lccn.loc.gov/2022025481

LC ebook record available at https://lccn.loc.gov/2022025482

Cover Design: Wiley

Cover Images: © Cover and interior images courtesy of West Technology Systems Limited

List of Contributors

Jocelyn V. Abonamah

Visiting Scientist Program

Research and Support Unit

Federal Bureau of Investigation Laboratory Division

Quantico, VA

USA

Christoffer K. Abrahamsson

Department of Chemistry and Chemical Biology

Harvard University

Cambridge, MA

USA

Alina Astefanei

Van't Hoff Institute for Molecular Sciences

Faculty of Science, Analytical Chemistry Group

University of Amsterdam

Amsterdam, The Netherlands

Arian van Asten

Van't Hoff Institute for Molecular Sciences

University of Amsterdam

1090 GD Amsterdam

The Netherlands

and

Co van Ledden Hulsebosch Center (CLHC)

Amsterdam Center for Forensic Science and Medicine

University of Amsterdam, Van't Hoff Institute for Molecular Sciences

1090 GD Amsterdam

The Netherlands

Graceson Aufderheide

Molecular Vista, Inc.

San Jose, CA

USA

Jeffrey G. Bell

Department of Chemistry and Chemical Biology

Harvard University

Cambridge, MA

USA

Charles A. Bishop

CA Bishop Consulting Ltd.

Consultant on Vacuum Deposition Technology

Leicestershire

UK

Robert D. Blackledge

Retired, formerly Senior Chemist

Naval Criminal Investigative Service

Regional Forensic Laboratory

San Diego, CA

USA

and

8365 Sunview Drive

El Cajon, CA 92021

USA

Candice Bridge

National Center for Forensic Science and the Department of Chemistry

University of Central Florida

College of Sciences

Orlando, FL

USA

Christopher Deeks

Channel Manager EMEA – Surface Analysis at Thermo Fisher Scientific

Joris Dik

Materials Science and Engineering

Delft University of Technology

2600 AA Delft

The Netherlands

Joseph Donfack

Research and Support Unit

Federal Bureau of Investigation Laboratory Division

Quantico, VA 22135

USA

Brian A. Eckenrode

Research and Support Unit

Federal Bureau of Investigation Laboratory Division

Quantico, VA 22135

USA

Shencheng Ge

Department of Chemistry and Chemical Biology

Harvard University

Cambridge, MA

USA

Alwin Knijnenberg

Netherlands Forensic Institute

2490 AA The Hague

The Netherlands

Maria Lawas

Visiting Scientist Program

Research and Support Unit

Federal Bureau of Investigation Laboratory Division

Quantico, VA

USA

Annelies van Loon

Rijksmuseum

1070 DN Amsterdam

The Netherlands

Roselina Medico

olam food ingredients (ofi) Department of Plant Science

Koog aan de Zaan

The Netherlands

Cyril Muehlethaler

Department of Chemistry, Biochemistry and Physics

University of Quebec

Trois‐Rivières, QC

Canada

Kandyss Najjar

National Center for Forensic Science and the Department of Chemistry

University of Central Florida

College of Sciences

Orlando, FL

USA

Padraic O'Reilly

Molecular Vista, Inc.

San Jose, CA

USA

Sung Park

Molecular Vista, Inc.

San Jose, CA

USA

Claude Roux

Centre for Forensic Science

University of Technology Sydney

Australia

Ryan Schonert

VUV Analytics, Inc.

Cedar Park, TX

USA

George M. Whitesides

Department of Chemistry and Chemical Biology

Harvard University

Cambridge, MA

USA

and

Wyss Institute for Biologically Inspired Engineering

Harvard University

Cambridge, MA

USA

and

Kavli Institute for Bionano Inspired Science and Engineering

Harvard University

Cambridge, MA

USA

Foreword

I have known Robert Blackledge for more than 20 years. We started communicating when one of my students began some research on the forensic analysis (and interpretation) of condom lubricants. I was immediately impressed by his willingness to openly share his knowledge and expertise to the overall benefit of forensic science in general and the field of trace evidence (or microtraces, as I would prefer to call it) in particular. This field has always been one of my strong interests since studying at the University of Lausanne, Switzerland, working under Professor Pierre Margot.

Microtraces are the product of a one‐off event that occurred in the past. As a result, they are often incomplete, imperfect, or degraded. They are anything but uniform. Further, they can take almost infinite shapes or forms. Finally, microtraces are rarely discovered as stand‐alone entities but usually mixed with other materials that were already present on the relevant substrate before the event generating them; sometimes, other materials may contaminate this complex matrix after the transfer event but before the microtraces discovery and collection.

As a result, microtraces detection, recognition, examination, and interpretation are often challenging and require a great deal of critical thinking resting on a sound scientific approach and reasoning. However, these microtraces can often hold the key to solve complex problems, including reconstructing what happened or who was involved. There are ample examples of cases where microtraces brought a breakthrough. Some of them are included in this book.

Unfortunately, over the last 20 years, the value and effective use of microtraces in forensic science has been diluted for a variety of reasons, mostly associated with the focus on high‐throughput laboratories increasingly operating in a mechanistic way, following what some call a “pill factory paradigm.” At the same time, it has been refreshing to see some great work and long‐lasting passions in this field. Anyone who has had the privilege to know Robert Blackledge will agree with my contention that he is a prime example in this category. I will always remember his passionate contributions to the multiple discussions at the National Institute of Justice Trace Evidence Symposia between 2007 and 2011.

With this passion and career‐long experience, Robert Blackledge wrote this book, along with the contributions of many leading experts in their field. The title, Leading Edge Techniques in Forensic Trace Evidence Analysis, perfectly reflects the purpose of this book. On the one hand, it systematically presents microtrace types that are not covered by traditional forensic science textbooks. Examples include shimmer particles in cosmetic samples, glitter, and other flakes. To some extent, due to their extreme variability and outstanding transfer and persistence abilities, these particles could be considered as cutting‐edge microtraces or ideal trace evidence, as has been previously reported.

On the other hand, this book presents cutting‐edge technology and methods that, similarly, are not commonly discussed in other forensic science textbooks. These techniques may rarely be found in the average crime laboratory. However, the forensic science community needs to know they exist, and can provide crucial findings in some cases. Therefore, it is essential to improve our knowledge about them and to recognize the case circumstances where they can be exploited to our benefit.

Leading Edge Techniques in Forensic Trace Evidence Analysis is therefore not a handbook on microtraces; there are many existing examples of these. This book deals with selected microtrace types, techniques, and problems. It will be most useful to practicing forensic scientists working in microtrace (trace evidence) laboratories; it will further expand their expertise in this field. It will also be a valuable reference for students, educators, and researchers engaged in forensic science. It is hoped that it will stir some new or renewed passion for microtraces research. Finally, other groups may benefit from reading this book, such as attorneys, judges, and novel writers. They may find critical answers to some questions raised in a case.

Leading Edge Techniques in Forensic Trace Evidence Analysis fills a gap by presenting less commonly discussed forensic science topics. It further illustrates and reinforces the value of microtraces in investigations and court. It is hoped it will inspire and stimulate the reader in showing interest and perhaps garnering more support for microtraces. This field is seminal to forensic science and remains one of its most fascinating areas. This book should well serve this cause.

Distinguished Professor Claude RouxCentre for Forensic Science,University of Technology Sydney, AustraliaPresident, International Association of Forensic Sciences

Preface

This book is a sequel to the book published in 2007, Forensic Analysis on the Cutting Edge: New Methods for Trace Evidence Analysis, edited by Robert D. Blackledge. As with the previous book, featured are either types of trace evidence having received little previous attention or new and better methods for trace evidence characterization.

As far as new and better methods for trace evidence characterization are concerned, many of the methods although relatively unknown to the forensic science community, have for years been used, studied, and improved by industry, scientific instrument manufacturers, and large university research groups.

Why this antipathy by the forensic science community as far as looking into and implementing new methods and instrumentation? One example that particularly puzzles me is the lack of interest in X‐ray photoelectron spectroscopy (XPS). Increasingly today we encounter objects that have one or more very thin surface layers. XPS is a surface analysis method that applies to all elements except hydrogen and helium. With a penetration depth of not much deeper than 10 nm, XPS results are not complicated by the composition of the particle core. It not only is quantitative as far as element concentration is concerned, but also provides an element's oxidation state and identifies those elements to which it may be bonded. Because carbon has so many oxidation states and elements to which it may be bonded, XPS is particularly useful for characterizing very thin surface layers that may be polymers.

In 2010, the paper “The potential for the application of XPS in forensic science,” by John F. Watts, Professor of Materials Science, University of Surrey, UK, was published in Surface and Interface Analysis 42(5): 358–362 (DOI: 10.1002/sia.3367). A truly outstanding and visionary paper, it included examples and case histories. And yet it was largely ignored by the forensic science community. I should think that among the forensic scientific community it would have received a reaction akin to that of biochemists to advances in DNA profiling.

It would seem that forensic scientists today actually working in crime laboratories prefer to beaver away like clerks in a Charles Dickens novel using validated protocols rather than have the temerity to try something new.

It is my fervent hope this book helps push many of these analytical methods toward acceptance and use by the forensic science community.

Robert D. BlackledgeSan Diego, CA

December 2020

1Forensic Analysis of Shimmer Particles in Cosmetic Samples

Kandyss Najjar1, Robert D. Blackledge2, and Candice Bridge1

1National Center for Forensic Science and the Department of Chemistry, University of Central Florida, College of Sciences, Orlando, FL, USA

2Naval Criminal Investigative Service, Regional Forensic Laboratory, San Diego, CA, USA

1.1 Introduction

Shimmer particles are commonly observed in daily life. From cosmetic products to paint samples, shimmer particles are readily present. However, despite its common presence, it has not been readily considered in the forensic trace evidence community as a form of contact evidence.

In this book's first edition, the chapter on glitter analysis mentioned that glitter and shimmer were often confused with each other [1]. Although both are ingredients in cosmetic products, they are easily distinguished by a cursory microscopic examination. In addition to microscopic analysis, there are fundamental chemical differences that differentiate these items. Regardless of the chemical differences, one property that might be common between these items is the potential to be an ideal contact trace evidence with strong indications of association between two people or a person and a physical item.

The previous glitter chapter in the first edition of this book asked the question: What are the properties of the ideal contact trace? To answer this question, the authors listed seven properties that would make any item an ideal contact trace sample. Based on these criteria, glitter can be considered an ideal contact trace material. The next question is – can shimmer particles be considered an ideal contact trace?

In this chapter, we discuss the chemical properties of shimmer particles, how these particles can be recovered as trace evidence samples, and the most appropriate instrumental methods for analyzing these samples. It will also be discussed how a Questioned and Known shimmer sample can be compared in a forensic casework setting. Through these discussions, it will be demonstrated that shimmer particles can also be considered an ideal contact trace evidence in addition to glitter samples. Although glitter has been demonstrated to be a critical associative evidence in numerous criminal investigations, to date, shimmer has been largely ignored by criminalists.

1.2 What is Shimmer?

Although this chapter focuses on cosmetic shimmer, many other products include shimmer particles. In the automotive paint industry, shimmer is known as an “effect pigment.” Kids and adults use them in creating arts and crafts. There are many commercial glue and pen products containing both glitter and shimmer. Moreover, particles have also been incorporated into everyday clothing and shoes, as well as in costumes for special events such as Halloween and Mardi Gras. They are even used for decorating greeting cards and ornaments used during holidays such as Thanksgiving and Christmas.

The focus of this chapter is on the identification of shimmer particles used in cosmetic products and personal hygiene products. Such products include lipstick, foundation, eye liner, hair spray, body lotion, and more. Cosmetic products use mica particles with different layer thicknesses of varying metal oxide coatings to achieve various shades of a certain color [2]. This is done to satisfy the ever‐increasing demand for new colors in cosmetics [3]. For instance, some silver pigments are created by coating with titanium dioxide to produce shades ranging from soft silver to dazzling silver. In contrast, other natural or earth‐toned colored cosmetics use iron oxide to obtain shades ranging from soft bronze to bright red. Since shimmer can be found in various cosmetic products, and most are intended for everyday wear rather than just for special occasion, as a result, shimmer particles may potentially transfer during close personal assaults and can be used as a form of trace evidence.

1.2.1 Shimmer versus Glitter

Many people assume that glitter and shimmer are the same, when, in fact, they are fundamentally and compositionally different. Cosmetic glitter is a man‐made product that is usually composed of either tiny pieces of aluminum foil, plastic without a metallic coating, or plastic that has an aluminum layer. It typically starts off with polyester sheets [1], such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) that may have been painted with pigments approved by the U.S. Food and Drug Administration (FDA). These sheets are then cut into tiny pieces with typical shapes of hexagons, squares, or rectangles. Hexagonal shapes are most common, followed by the squared shape. Other manufacturers may create unique glitter shapes such as stars or moons [1].

In her article from The New York Times, What Is Glitter?, Caity Weaver described glitter as “aluminum metalized polyethylene terephthalate” [4]. Glitterex Corporation was presented as one of the largest glitter manufacturers in the United States (Cranford, NJ), which sells glitter that is mainly composed of thin Mylar PET film. To achieve a rainbow‐like colored glitter, i.e., holographic glitter, a fine layer of vapor‐deposited aluminum is placed onto the polyester film and then embossed with a diffraction grating pattern so that light reflects at different directions simultaneously. Finally, some of their glitter is composed of multi‐layered plastic of various refractive indices, with each layer more than 230 nm thick, to achieve different colors at different incident angles [4].

On the contrary, shimmer particles are primarily comprised of mica substrates, which are complex aluminosilicate crystals that readily separate into thin flat sheet‐like layers. Mica is a naturally occurring mineral but can also be synthesized commercially. Cosmetic shimmer is primarily comprised of mica particles that have been coated with different types and thicknesses of metal oxides to generate different colors or effects. Furthermore, although shimmer particles may fall into a certain size range, their shape is totally irregular and random.

Glitter has been used previously as associative evidence in real‐world cases [1, 5, 6], however, shimmer has not been evaluated despite its potential value as associative evidence as well. Little research has been conducted on shimmer analysis as a means of trace/associative evidence. The examination and evaluation of shimmer may indeed expand the scope of forensic particle analysis that is currently available by providing another type of associative evidence to evaluate and a means to compare known and unknown shimmer particles that may have transferred during a close personal contact.

1.2.2 Shimmer Composition and Use

Albeit being mainly overlooked by criminalists, shimmer is very well known by chemists in various industries, including the cosmetics industry, the craft industry, and the automotive industry; and new and improved forms of shimmer are steadily being introduced into the commercial marketplace. The wide variety of shimmer applications increases its potential value as trace evidence, and the fact that many commercial cosmetic products contain several different types of shimmer particles at different relative amounts makes samples with shimmer easier to distinguish from one another.

Shimmer mainly consists of pieces of mica of a certain size range that have been coated with titanium dioxide (TiO2) of uniform thickness. This chapter will focus on coated mica as it is the most common type of shimmer.

The most common and abundant forms of mica are muscovite and biotite [7]. Biotite mica has the general formula K(Fe, Mg)3(AlSi3O10)(OH)2, where the potassium (K) can be found bound to either iron (Fe) or magnesium (Mg). Biotite is typically darker in color than muscovite, in usually a black or dark brown color [7, 8]. Biotite is used as a filler or insulator in various electrical and construction applications [7]. The mica used in most cosmetic products is muscovite. Although its general formula is KAl3Si3O10(OH)2, depending on geographic location the formula is variable K(Al, Cr, Mn)3Si3O10(OH)2, where the potassium could be bound to either aluminum (Al), chromium (Cr), or manganese (Mn). When only K is bound to Al, muscovite is most commonly clear in color, sometimes occurring in light shades of brown, green, yellow, or rose [9]. When Al is substituted with Cr, the mica is referred to as Fuchsite or Chrommuscovite and the mineral is generally green in color [9, 10]. Manganese rich muscovite mica, when Mn is in the place of Al, occurs in colors ranging from pink to red and is known as Alurgite [10]. These chemical differences provide the first manner in differentiating mica substrates.

Once the cosmetic sample has been applied, the shimmer particle is intended to lie flat on the surface. The longest dimension may range from as little as a few microns up to several hundred, but their thickness is typically one micron or less. Although quite small, shimmer particles cannot be considered nanomaterials.

Mica particles use the basics of thin film light interference to achieve their color shifting properties [11]. Light interference occurs in one of two ways. Constructive light interference results in higher amplitudes when two waves are in phase, whereas destructive interference causes the resultant wave to lower in amplitude when two waves are out of phase at a phase difference of half the wavelength. The condition for maximum interference is λ = 2ndcosθ, where λ is the wavelength, n is the refraction index of the spacer, d is the spacer thickness, and θ is the angle of incidence of the light.

Most shimmer particles will be constructed as a sandwich, where the mica, i.e., a semi‐transparent spacer, is placed in between two semi‐reflective metal oxide layers. The combination of a specific spacer and semi‐reflective layers is referred to as a Fabry–Perot interference filter [11] (refer to Figure 1.1). Since a specific color is represented by a narrow wavelength region, various colors would be observed with different incident angles [11]. These optical properties of metal‐coated mica shimmer particles can help individualize these cosmetic shimmer particles.

To develop the colors observed via thin film interference, the incident light interrogates the semi‐reflective metal‐oxide layer first where two outcomes occur. The incident light can be reflected by the metal‐oxide layer and due to the semi‐reflective nature the incident light can also be transmitted. The thickness of the metal‐oxide layer on top of the mica substrate will affect the resulting color observed. At the interface of the metal‐oxide and mica layers, the light can be reflected, and/or transmitted into the mica substrate. Based on the thickness of the metal‐oxide layer and its refractive index, the reflected light at the interface should narrow the wavelength selectivity of the light and as a result influence the color observed by the user. The different colors of shimmer that may be achieved are due to interference between reflected light at the metal‐oxide surface and at the interface of the metal‐oxide and mica layers. A fuller discussion is presented by Jiang et al. [12] on the basic theory behind optically variable pigments such as metal‐oxide‐coated mica particles.

Figure 1.1 Shimmer thin film light interference based on the concept of a Fabry–Perot filter.

Since the reflected color depends on the thickness of the TiO2, and because mica may not always cleave so that the top and bottom surfaces are perfectly flat (i.e., there are layers that partly overlap), the thickness of the TiO2 layer may show some variation and the observed reflected color may not be as pure or monochromatic. More expensive, synthetic mica, KMg3AlSi3O10F2, often referred to as “synthetic fluorphlogopite,” has excellent surface smoothness. Synthetic mica is sometimes preferred over its natural alternative since it may be used to create brighter and more radiant shimmer colors. Other less common substrates include alumina, silica, bismuth oxychloride crystals, and calcium aluminum borosilicate (glass) [13, 14]. Synthetic shimmer substrates are also selected by some companies to avoid human rights implications of using child labor in the mining of natural mica [15].

1.3 Shimmer Detection and Collection

In the 1900s, a French criminologist named Edmond Locard opened the world's first crime lab in France and is well known for his most famous book titled Treaty of Criminalistics[16]. Locard believed that “every contact leaves a trace” and developed what is known as Locard's Exchange Principle [16, 17]. In his book Crime Investigation: Physical Evidence and the Police Laboratory, Paul Kirk expresses the Locard's Exchange Principle as “Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only fingerprints or footprints, but hair, fibers, glass, paint, blood or others. All of these and more, bear mute witness against him” [18]. This principle suggests that even if perpetrators attempt to mitigate evidence left behind at a crime scene, trace evidence that is often overlooked may be used to connect or link them to the crime scene or the victim. Therefore, since many perpetrators are not aware that cosmetics can be a type of trace evidence, Locard's rule can be applied to cosmetic and/or shimmer transfer as well.

1.3.1 Detection of Cosmetic Stains

Shimmer particles can easily be detected at a crime scene using common methods that are generally present in most collection kits. Cosmetic smears can be found anywhere at a crime scene, depending on the type of crime that was committed, but the most common locations are on clothing, bed sheets, or other physical items (i.e., tables, walls, etc.).

The easiest detection method to locate shimmer particles is to use a flash light. When searching large areas of interest around the crime scene, the shimmer particles will reflect the light and can then be easily detected by the naked eye.

An ultraviolet (UV) light source or light box is another method that can be used to detect cosmetic smears on fabric samples. Most white or light‐colored garments bear traces of a fluorescent fabric brightener and when outdoors or under UV‐containing light rays, the fabric appears “whiter than white.” This is because UV‐light rays impinging on the garment cause the fluorescent molecules to emit “white” light. Therefore, if any stains or smears are present on the garment, even if they are colorless and invisible under ordinary light, once placed in a UV light in the dark the smears will appear as a shadowy area on the garment. This is because the smear blocks some of the fluorescent light being emitted from the garment. Although the smear may primarily consist of the vehicle used in the commercial cosmetic containing the shimmer, i.e., lipstick, which may not exhibit fluorescence, this will be a prime location to collect shimmer particles.

1.3.2 Collection of Shimmer Particles

Shimmer particles transferred from cosmetic products may be collected in a manner similar to the suggested collection of glitter particles in this book's first edition [1].

Whether a few individual particles or cosmetic smears were found, the simplest way to collect shimmer samples is to stub the sample with Post‐it® notes. The sticky notes could simply be folded and placed into small re‐sealable zipper bags to prevent losing the sample prior to analysis. Moreover, all critical information about the collection process can be written onto the sticky note itself prior to being sealed for subsequent analysis. Tape lifts may also be used, but the glue from tape is stronger than the Post‐it notes and may contaminate or destroy the evidence upon extraction of the particle from the tape for analysis. One caveat to using Post‐it notes is that they can only collect from smaller items or areas, whereas tape lifts may be used on larger items or areas of interest.

If only a smear was located on a hard surface, i.e., a table, the smear may be collected using a cotton swab or scraped off using a spatula. However, with this collection method it will be necessary to have a good extraction method to separate the shimmer particle from the cosmetic vehicle.

1.4 Analysis of Shimmer Particles

It is best practice to first analyze particles using a stereomicroscope or digital compound microscope to obtain size and morphology information. Afterward, other analytical techniques may be utilized to ascertain other chemical information. Techniques commonly used to analyze forensic evidence include, but are not limited to, optical microscopy, Fourier‐transform infrared spectroscopy (FTIR), Raman spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy – energy dispersive X‐ray spectroscopy (SEM‐EDS). Most of the instrumental techniques presented herein are based on the current research conducted by Najjar and Bridge.

1.4.1 Sample Extraction and Preparation

After collection, particles can be removed from the collection media, e.g., Post‐it notes or tape lifts, using tweezers and subsequently cleaned. When shimmer particles are in cosmetic products, they are generally contained in a vehicle (e.g., lotion, eyeliner, nail polish, or lipstick) and as a result an appropriate extraction method is needed to separate the shimmer particles from the vehicle. After collecting shimmer particles, it is also possible that there may be traces of the vehicle adhered to the recovered shimmer particles. The particles can then be separated from the cosmetic matrix using a simple hexane wash and filtration process [2]. The particles are then ready for instrumental analysis.

1.4.2 Digital Microscopy

Forensic evidence is typically first analyzed under a stereo‐binocular microscope. The stereomicroscope allows for three‐dimensional visualization of the item so the analyst can observe its structure, morphology, and size. New advances in the microscopy field allow for a more robust digital analysis of samples where size, color, particle count, and other features are automatically detected via machine‐operated microscopy software.

Since shimmer shape, size, and color are very irregular and random, it is quite difficult to gain such information using digital microscopy. Despite the irregularity in size, specifically, it is suggested to conduct analysis based on a size range rather than an average size. Based on recent research completed by the authors Najjar and Bridge, subtle differences in size ranges were observed between different shimmer samples. To demonstrate the subtle differences between different shimmer powders, the size ranges were determined and subsequently compared and presented herein.

Shimmer powder, which had not previously been incorporated into a vehicle, was placed onto a microscope slide and was smeared using a Kimwipe to obtain individual layered particles. Shimmer particles may be very small and are harder to separate based on size simply by visual observation. Therefore, a Keyence VHX‐6000 digital microscope was used to obtain size measurements of area, perimeter, minimum diameter, and maximum diameter for the shimmer particles in the field of view of the microscope. Only individual layered shimmer particles were used for the analysis. Some shimmer specks were omitted from size measurements due to overlap with other particles, or because part of the individual shimmer particle was cut off the microscope's image field of view. Table 1.1 shows an example of the size measurements of two red shimmer samples analyzed. In the table, “Low” and “High” signify the low‐end and high‐end size range limits, respectively. Samples used for this research study were purchased from Just Pigments (Tucson, AZ). Based on their manufacturer details, Red Wine CP‐504 is composed of natural muscovite mica coated with iron oxide, whereas Superstar Red CP‐7059 is made up of synthetic fluorphlogopite, coated with titanium dioxide, iron oxide, and tin oxide. Table 1.1 displays the difference in size ranges between the natural and synthetic shimmer samples. For instance, Red Wine shimmer had particles with areas ranging from 24.2 to 1895.4 μm2, while Superstar Red shimmer had a range of 76.2–7170.9 μm2. Further comparisons between natural and synthetic mica samples of different colors (e.g., green, blue, and violet) showed similar results, with the synthetic samples always larger in size on average. Figure 1.2 shows the Red Wine and Superstar Red shimmer under the Keyence microscope in both reflectance (Figure 1.2a,c) and transmission (Figure 1.2b,d) light. Both shimmer samples were analyzed at various angles of impingent light to demonstrate the color‐shifting properties of mica pigments (Figure 1.3).

Table 1.1 Microscopic size measurements obtained for Red Wine CP‐504 (natural mica) and Superstar Red CP‐7059 (synthetic mica) shimmer samples from Just Pigments.

Shimmer name/product #

Low area (μm

2

)

High area (μm

2

)

Low perimeter (μm)

High perimeter (μm)

Low max diameter (μm)

High max diameter (μm)

Low min diameter (μm)

High min diameter (μm)

Red Wine CP‐504

24.2

1895.4

17.5

176.1

 6.2

 58.4

4.0

44.1

Superstar Red CP‐7059

76.2

7170.9

30.7

408.3

11.6

175.3

6.9

89.6

Figure 1.2 Microscopic images of (a and b) Red Wine CP‐504 in reflectance and transmission modes. Microscopic images of (c and d) Superstar Red Wine CP‐7059 shimmer samples in reflectance and transmission modes. All images were obtained at 500× magnification.

Regarding color analysis, although an observer may view both of these samples as red by the naked eye, the synthetic sample appears more translucent under the microscope (Figure 1.2c,d). Thus, natural and synthetic samples may be differentiated using microscopy alone. However, although a difference in color may be visually observed among samples, a reliable objective color measurement, i.e., Red‐Blue‐Green (RGB) values, may not be obtained per sample. As shown in the figures, there are color differences within single particles of a certain shimmer sample, most probably due to mica's imperfectly flat cleavage.

Figure 1.3 Microscopic images of (a) Red Wine CP‐504 and (b) Superstar Red Wine CP‐7059 shimmer samples in reflectance mode at different light angles represented by (latitude°, longitude°).

1.4.3 Infrared Spectroscopy

Infrared spectroscopy is a common technique used in forensic casework. Recent work has evaluated FTIR as an analytical method in the forensic analysis of cosmetic shimmer. Gordon and Coulson aimed to differentiate 53 distinct cosmetic foundations based on FTIR spectral differences and achieved a discriminating power of 98.3% [19]. Moreover, a second group detected and analyzed fingerprints contaminated with various cosmetics. Researchers obtained FTIR spectral imaging of each sample by attaching a focal plane array (FPA) detector to the IR spectrometer [20]. FTIR imaging was achieved because the FPA detector allows for simultaneous collection of one spectrum per pixel [21]. The researchers determined that different cosmetic samples, i.e., body butter and lip gloss, may be characterized based on the mid‐IR region (400–4000 cm−1). Differentiation of samples due to the identification of fundamental molecular vibrations was achieved [20]. An example of the vibrations observed in the mid‐IR region for muscovite mica shimmer samples is presented in figure 3 from Ref. [22]. This region shows OH vibrations at 3622 cm−1 and different SiO4 vibrations (Si–O and Si–O–Si) around 1063, 1028, 993, and 926 cm−1. In comparison, figure 5 from Ref. [22] presents the IR spectrum for biotite mica which has a similar overall spectrum, but there are differences between the two spectra in the fingerprint region [22]. The medium to strong peaks around 500 and 1100 cm−1