Who doesn’t like a silvery shine to their greeting cards? Or maybe a beautiful tint of shine to their highlighters. One in all, glitters are used in a variety of places which might or might not have skipped the eye, but for a forensic eye… It might turn out to be crucial evidence! Mind-blowing Right? Who would have thought that your smoky eyeshadow that sparkled at the funky parties or the pretty glitter powder that you sprayed to make your Rangoli stand out from the rest could actually lead to solving a crime!
Fibers, glass, hairs, and paint are the conventional evidence that is talked about almost every day in forensics, and glitter might be seen as an unusual sort of trace evidence. However, this form of trace evidence has a greater chance of being discovered than in the past due to the material’s prevalence in clothes, cosmetics, and art and craft items. Glitter has been observed in a variety of incidents, including homicide, kidnapping, assault, and unlawful use of a vehicle. Although glitter cannot be used to identify a specific person, it can link a suspect to a victim, a scene, or the victim’s position in a vehicle accident.
The general manufacturing process includes vacuum depositing metal onto a thin polymer film and coating it with a specific color. Polyester, polyvinylchloride, and polypropylene are some of the various polymer kinds that have been recorded. The shape of glitter has been somewhat controlled by factors like cost and waste. Additionally, glitter can vary in size and thickness, as well as a variety of hues. Another distinguishing characteristic of glitter is variation in the layering order. Glitter is a kind of trace evidence that has the potential to be extremely discriminating because of a combination of class characteristics.
Individual glitter particles can be easily found with a flashlight in low light because they reflect light like small mirrors when separated from one another. The glue on Post-It Notes is powerful enough to remove individual glitter flecks from the majority of surfaces, but it is also weak enough such that the particles can be picked off without damage and without transfer of adhesive. Additionally, the notes come in helpful for recording all the pertinent evidentiary paperwork (case number, place of discovery, date/time, technician’s initials, etc.).
Nearly invisible: Most of the time, the suspect does not realize that he is carrying glitter on himself because it is not very obvious as in the case of blood.
High probability of transfer and retention: Glitter particles are more likely to transfer since they are small and lightweight in nature.
Highly individualistic: There are different categories in which glitter particles can be classified which will keep strengthening its evidentiary value. Those are size, shape, thickness, specific gravity, morphology, number and thickness of layers, the chemistry of each layer and so on.
Easily characterized: Only a single glitter particle is required, although more particles would better argue against accidental transfer from a source totally unrelated to the victim or crime scene.
Computerised database capability: data from actual case samples can be entered into the system to make a database of all the parameters of glitter.
Can sustain in different environments: After several years, glitter particles detected in auto carpeting could still be compared; the same was true of glitter particles discovered in the hair of a deceased person who had been exposed to the elements for weeks.
Color: Some companies offer as many as 44 different colors but we cannot find 44 colors upon examining individual particles. Moreover, many products do not contain any dyes or pigments at all. However, it would be preferable to have an objective, machine-determined measurement of color to remove subjectivity and allow color measurements to be placed into a searchable database. Using glitter as associative evidence in a kidnapping/sexual assault case, a QD1 1000 Microspectrophotometer (Craic Technologies, Altadena, CA, USA) was utilised to compare colours.
Morphology: While the majority of glitter particles appear the same on each surface, some do not. Some might have a surface with additional color, while others might have an aluminized layer with plastic layers on top. Higher magnifications (700x or greater) allow for the observation of these distinctive morphologies, and ATR infrared microscopy can be used to compare the chemistries of the two surfaces. The examiner must make sure that any apparent surface morphology is not caused by contamination or vehicle traces on the particle’s surface.
Shape: Examining glitter particles found on tape lifts under reflected light with a stereo binocular microscope or a video microscope set to a modest magnification makes it simple to discern their shape. Hexagonal particles are the most common followed by square and rectangular ones. It is rare to find a product that mixes different shapes. Their associative value would be high if a mixture of these particles identified in evidence items is linked to a suspect and also to the victim.
Cross Section: Glitter can be cross-sectioned manually using a stereo binocular microscope or automatically using an embedding medium and a microtome. To cross-section by hand, just adhere the glitter foil to some adhesive tape or the sticky side of a Post-it note, and use a stereo knife to cut at a 90-degree angle microscope. A new blade for a razor or scalpel and some absorbent material substance (to prevent cut marks on your microscope’s stage) may be used. The angle of the cut must be reduced if the goal of the cross-sectioning is to obtain a clean layer of material for FTIR examination.
Infrared Spectra: Even though they are translucent, glitter particles are too thick visually to produce high-quality FTIR spectra in the reflectance or transmission modes, even when they are opaque (contain a metal layer). However, using the attenuated total reflectance (ATR) diamond objective on an FTIR microscope results in excellent, searchable spectra. Another benefit is that no sample preparation is necessary other than making sure the glitter particle’s surface is clean. Remember that each glitter particle has two faces. It’s possible that the polymeric material on one side differs from that on the other. On one side, certain glitter particles have a distinct coverage.
Raman Microspectroscopy: This would be the best method for identifying the various polymer layers in glitter particles.
- B. Blackledge, “GLITTER as Forensic Evidence.” [Online]. Available: https://projects.nfstc.org/trace/docs/final/Blackledge_Glitter.pdf
- R. D. Blackledge, Forensic Analysis on the Cutting Edge. John Wiley & Sons, 2007.
- “American Society of Trace Evidence Examiners,” http://www.asteetrace.org. https://www.asteetrace.org/glitter (accessed Oct. 20, 2022).
About the Author
Saptarshi Rao is currently pursuing M.Sc. in Forensic Science from Rashtriya Raksha University