Perspectives from Bridge [email protected]: Glitter and Shimmer as Forensic Tools

 Perspectives from Bridge Group@NCFS: Glitter and Shimmer as Forensic Tools

Welcome to Forensic’s first (of four) installment of “Perspectives from Bridge [email protected]” The National Center for Forensic Science at the University of Central Florida has a 20+ year history of research and partnership with the forensic science community. This column is authored by Danielle Green, a Ph.D. student in the lab of Candice Bridge, a pioneer in the field of trace forensic analysis. In four columns over the 2021 year, Green will bring readers into the Bridge Group Lab, sharing the incredible research going on there as the scientists fight for victim justice.  

"Text me when you get home."

"If you don't hear from me by 11pm, this is who I was with."

"Hey I am leaving the bar. Can I talk to you until I get to my car?"

These are common phrases for women. Strangely the idea of women constantly being in danger is a societal norm more than a cause for concern. The involuntary adjustments made by women traveling in their day-to-day lives would seem outrageous to some, but is familiar to so many others. Ask any woman in your life, and she will most likely say she has done at least one of the following: parked in a well-lit and easily viewed area of a parking lot, called a trusted friend when traveling from place to place, held her keys in her hand as a makeshift weapon, sent an uncomfortable glance across the bar silently asking a friend to help, stood uncomfortably in a room dominated by men, or changed shoes before leaving to force a more purposeful and unwelcoming stride in the hope of deterring conversation.

You ask yourself why women ingrain this sort of survival in the minds of young girls and follow strict guidelines long into adulthood. The response is simple. The world can be unsafe for a woman to merely exist. Women like Sarah EverardAmanda Berry, Michelle Knight, and Georgina "Gina" DeJesus are a few of many that have demonstrated the need for better respect for women and the severity of violence that occur against women.

Work needs to be done by law enforcement and scientists to treat women with the respect they deserve and be an advocate for those whose voices can no longer speak for themselves. One researcher works to do just that.

At the National Center for Forensic Science, Candice Bridge leads a team of students working diligently to help the victims of violent crimes by shedding light on some of the most unlikely trace material possibly found on a victim or suspect.


Tiny pieces of metallic foil or polyester films found in lotions, cosmetics, paints or the card you mailed to Grandma last year. These macroscopic flecks have the uncanny ability to show up in the least expected places. Research conducted by Kandyss Najjar, a Ph.D. student in the lab of Bridge, investigates the possible transfer of cosmetic products through skin-to-skin, skin-to-fabric or fabric-to-skin contact.  

Early work completed by M.C. Grieve in 1987 and Robert Blackledge in 2007 theorized that not only do glitter particles readily transfer, but if analyzed using highly discriminating techniques, the particles can be characterized and differentiated based on their chemical composition. Glitter can be studied using various methods, including Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM-EDS) to ascertain the chemical and elemental properties.

Focusing on SEM-EDS, Najjar has had high success developing a protocol for the analysis of glitter and shimmer, a natural product composed of mica often found in cosmetic products. Through the research of 36 glitter and 40 shimmer samples, Najjar has created classification schemes for the discrimination or association of different particles into respective groups based on the chemical profile of the samples. Ideally, a good classification system would have samples of either the same color or manufacturer clustering together in a group. However, this classification system groups glitter or shimmer samples together based on similar elemental composition. The classification system can then take this information and group like-with-like or exclude samples due to lack of pertinent features. Therefore, when a new sample is analyzed using the same instrumental techniques and classified with this model, based on the presence or absence of these features, the unknown sample can be classified with like items.

Picture a bag of balls of different colors and shapes. Based on how well I can identify all the critical features of these various balls, I can use that information to create this classification scheme. In this bag, I have small red balls, large red balls, small green balls, and small yellow balls. Once I have used the proper tools to identify the balls' features, all that information is loaded into the classification model. The model might then take that information and create groups. The aforementioned model could include all the green balls in a group, all the yellow balls in a group, and the red balls in a mixed group with the small and large balls. After validating that my model is appropriate for grouping like samples into one of these three groups, I am now presented with a new ball. This unknown ball is a large green ball. The model initially created, can take the latest sample information and attempt to group it with similar samples. Let us propose that in our aforementioned model the colors of the balls are producing the most variance in the data. That would mean that when the classification model is presented with this large green ball, it will group that ball with the small green balls. Classification models are instrumental in forensics. When presented with an unknown sample, a classification model with high accuracy can guide the scientist to the sample's possible identity.

Najjar's classification schemes produced classification rates of 94.4 to 100%, giving high accuracy to the analysis of unknown samples. When asked what impacted her the most about this project, Najjar stated she was surprised to see how well the samples were classified based on her model, especially when investigating other emerging technologies like direct analysis in real time - high resolution mass spectrometry (DART-HRMS). DART-HRMS is a relatively new technology to the forensic community. Introduced in 2005 by R.B. Cody and J.A. Laramée, DART has shown to have promise in the analysis of trace materials, botanicals, explosive materials, and drugs.

Najjar started her project analyzing reference shimmer and glitter samples using SEM-EDS, white light microscopy, FTIR, and DART-HRMS. Once a classification scheme was developed with these standard samples and after validating her models, she tackled the question of how these samples transfer through various types of contact, i.e., skin-to-skin, skin-to-fabric, and fabric-to-skin. She has also investigated what effects heat and humidity can have on glitter and shimmer over a length of time. The last phase of her project will analyze "real world samples,” meaning makeup products claiming to contain glitter and/or shimmer particles. The goal is to extract out and analyze the trace particles and then attempt to classify the samples into one of the model categories. This will allow her to determine if the models that she developed can be used to new samples.

Najjar said she hopes to provide non-traditional analytical tools for examiners. Using the extraction protocols developed in her current work, samples found at crime scenes or on victims could be correlated with the manufacturer, generating necessary investigative leads. The goal of Bridge Group's work is to use what is available, i.e., sexual assault kits or residues found on the scene, and give the examiners the possibility to glean as much information as possible from the sample while being mindful of the massive caseload of forensic scientists. Not every sexual assault kit collected will contain biological material (i.e., DNA) connecting the assailant and the victim, and when that happens, those kits can still give pertinent information and be utilized instead of deemed unusable. Najjar is working to create the foundation for potentially developing a database that could be available for public use similar to the NCFS’s other databases, such as the Ignitable Liquids Reference Collection Database and the Sexual Lubricant Database.

Forensic science has had a reoccurring trend of developing novel and unique technologies to answer the questions presented in criminal investigations. Najjar views this work as no different. The big takeaway of her work is, "be mindful of the emerging technologies out there and be willing to consider out-of-the-box possibilities. Use a flashlight and do a quick sweep for a sparkle of light. Glitter or shimmer might be present. There are tools out there, and they might help draw the association between the victim, scene, and suspect."

Glitter and shimmer are everywhere. This trace evidence could be far more helpful than previously assumed with the assistance of Najjar and Bridge. Victims of sexual assault or contact-based harassment deserve to have every tool possible to aid them in difficult times. Tragedies like Sarah Everard might be prevented with the continuation of forensic science research and the willingness to expand the knowledge base.