Introduction
At present, cosmetics as trace evidence are not widely used in the forensic area. Current research involving cosmetics as trace evidence are biased towards lipsticks. Lipstick smears are frequently encountered in forensic laboratories as an important form of transfer evidence Ehara and Marumo (1998). There is little/hardly any on foundation and blusher samples as trace evidence.
Trace Evidence
Trace evidence consists of a wide-ranging group of physical evidence which includes microscopic material. Common trace evidence which may be encountered at a scene are materials such as; hair, fibres, paints, soils, explosives, glass and footwear/tyre impressions. Items which are recovered from either a crime scene, suspect or victim that may shed light on an investigation can be categorised as physical evidence, if they are recognised as having possible significance. In forensics trace evidence can be used to aid investigations by reconstructing a chain events De Forest (2001). The transfer of evidence occurs when there is a physical contact between two things wether that be two individuals, objects or individual and an object. The likelihood of this transference depends on the duration of the contact and the nature of surfaces Deedrick (2000). Trace evidence is classed as associate evidence because it has the ability to link two individuals or an indiviudal to a crime scene. For example, a paint chip from the car of a suspect may be found on the victim of a hit and run or a trail of blood from one location to where a victim has collapsed Gallagher and Thornton (2011).
Geneally trace evidence is indentified using a polarized light microscope. Different light conditions can reveal different parts of fibres (internal structure). Comparisons can be made using a comparison microsccope. A crime scene sample is compared to a reference/known sample (usually susepcts) and an analyst will determine if they have originated from the same source. Fibre evidence was used in the abduction and murder of Sarah Payne in 2000. Sarah’s shoe was found containing a large number of red fibres in the velcro strap. Upon examination, they matched the red fibres from her sweat shirt but, others matched the red sweatshirt found in the suspects van. Fibre evidence prodivded a link between Sarah and the shoe and the shoe with the van Pepper (2010). Chemical analysis can also be carried out on items such as fibres and paints through the use of micro Fourier Transform Infrared Spectrometer.
Locard’s Principle
Locards exchange principle states “whenever two objects come in contact with one another, a transfer of material will occur”. So, in a forensic context it simply means a suspect will leave something at and take away something from a scene Netzel (2005). Edmund Locard believed it was nearly impossible for a criminal to commit a crime without leaving some kind of trace evidence behind for example, hair, fibres or DNA. If someone commits a crime and come into contact with a victim/object they always leave traces of themselves behind at the scene which was not present before. On the other hand, they will also take evidence from the crime scene which was not present on them prior to entrance of the crime scene for example, fibres, hair, paint and other sources of trace evidence can attatch onto their clothing meaning the criminal will take them away with him Horswell and Fowler (2004).
Cosmetic as Trace Evidence
Edmund Locard was the first to show the significance of cosmetics as trace evidence in 1912. He proved that cosmetic dust found on a person could provide evidence of where a person had been. A body of a young women who appeared to have been strangled was found. Locard took scrapings of the material under a suspects fingernails and studied the particles under a microscope. He showed that the dust under a homicide suspect’s fingernail was chemically consistent with a face powder found in the victim’s room. This linked the suspect to the victims and Locard suggested he had picked up the powder while strangling his victim and taken it from the crime scene Nickell and Fischer (1999).
Cosmetic smears are a type of transfer evidence which are frequently found at scenes due to their widespread use and ease of transfer from person to person or person to material/object. They are deposited in minute sizes and are related to crimes of a violent/physical nature such as rape or assault where there is intimate contact between two people Choudhry (1991). Lipstick smears and face creams can offer valuable evidence which can link an offender to a victim at the scene of crime Challinor (1995). The presence of makeup (e.g. lipstick/foundation) on a suspect’s clothing can provide evidence during physical contact. Studies in New Zealand show that cosmetic foundation products are transferred to clothing during sexual assault cases Gordon and Coulson (2004). It is important as analysts use this evidence to determine if there has been contact between two people or to place a victim or
suspect at a mutual scene. Lipstick smears are the most common evidence with regards to cosmetics. A smear which may be found on a suspect’s clothing can provide a link between them and a female victim. Also, smears left on crime scene items such as cigarette butts from smoking and glasses/cups from drinking can place a victim/suspect at a crime scene Ehara and Marumo, (1998). Lipsticks have been used as mediums for writing threatening messages. A murder suspect wrote on a mirror in the home of his victim “For heaven’s sake, catch me before I kill more. I cannot control myself.” Babwin and Bernstein (2012).
Composition of Cosmetics
Most cosmetic types have similar bases and are made up with similar ingredients particularly powders, foundations and blush. They are made of various organic products, minerals, oils and pigments History of Cosmetics (2017). All ingredients within foundation and blusher cosmetics are added to either enhance the performance of the product by giving long lasting effects or to improve the finished look. Foundations can be either a cream or lotion which are used as a base for facial makeup. It colours the face and conceals blemishes to produce an impression of health and youth. Blushers are used to colour facial features, this is done by applying it to the cheeks to highlight the cheek bones or cover up any skin imperfections Cosmetics Info (2017). It is important to know what components are in the cosmetics which will be tested in this study. Once the components are known, it is easier to interpret the spectra produced from each sample. The most common ingredients and why they are used in the products are summarized below in Table 1.
Table 1: Ingredients commonly found in foundation and blusher and why they are used.
Ingredient Why is it used? Reference
Glycerine Hydrates the skin by absorbing moisture from the air and provides a skin barrier. 1
Hyaluronic Acid Gives deep hydration, used as an anti- aging product. 1
Lecithin A water attracting agent which hydrates and improves the texture of the skin. This allows the ease of spread onto the skin. 1
Dimethicone It gives a smooth texture without blocking pores and reduces redness of the skin. 1
Titanium Dioxide Primary coverage pigments which act as fillers making the cosmetic product more opaque. It is a colouring agent and gives a “whitish” finish. 1
Alcohol (Cetyl and Stearyl) Acts an emulsifier and emollient by mixing oil and water phases or vice versa. It is used as a lubricant and allows a product to spread easily. 1
Isopropyl Isostearate Fatty acids that act as emollients and binders, they condition the skin and hold all of the ingredients together. 1
Kaolin Oil absorbing powder which produces a white colour which is able to scatter light and reduce the skin’s natural colour. 2
Tocopherol Has anti-inflammatory properties and aids in moisturising the skin. 2
Parabens Prevents cosmetics from forming bacteria and fungus. 2
Glycerol Stearate Acts as an emulsifier and humectant by mixing oil and water phases together. It is able to absorb and retain moisture in the skin. 2
Ethanol Solvents used to dilute formulation. 3
Talc Acts as a filler ingredient which helps spread the primary coverage on the face. It is used as an absorbent, anti-caking agent and to improve the overall feel of the product. 3
Stearic Acid Acts as a surfactant cleansing and emulsifying agent. 3
Butylene Glycol Added to dissolve essential oils and synthetic flavouring substances. 3
Water Forms emulsions in which the oil and water components of the product are combined to form foundation. 3
Zinc Oxide Produce a white colour which scatters light and reduces the skin’s natural colour. 3
Mica Filler ingredient which can help spread the primary coverage pigments around on the face 2
References for the information in Table: 1 – History of Cosmetics (2017), 2- Romanowski (2017), 3- MedicineNet (2004).
Forensic Analysis of Makeup
There appears to be very little published research on makeup as trace evidence as a whole. A study based on foundation smears was carried out by Gordon and Coulson (2004) to determine the best discriminating technique between transferred foundation smears where, the samples are gathered from a known source. Fifty- three samples were smeared onto white cloth and left to air dry. Samples were scraped from the cloth and placed onto the machine for analysis. They were analysed through Fourier Transform Infrared Spectroscopy (FTIR), Gas
Chromatography with a flame Ionisation Detector (GC-FID) and Scanning Electron Microscopy – Energy Dispersive X- Ray analysis (SEM-EDX). All analysis were carried out in duplicate with a blank control (no foundation present on cloth) to rule out any substrate interference. The study found only a 5mm2 of light smearing was needed for detectable results. They found the discriminating powers for FTIR, SEM-EDX and GC-FID were 98.3, 93.8 and 82.0% respectively. A combination of all techniques achieved almost complete discrimination between the samples analysed and gave a discriminating power of 99.7%.
Kulikov et al (2012) analysed cosmetic foundation powders to determine if they were made of a traditional or mineral formulation. Thirty- nine cosmetic powders were underwent multi – elemental analysis using Dispersive X- Ray Fluorescence Spectrometry. Quantitative measurements were obtained for Al, Bl, Ca, Fe, K and Mg. The principal components allowed the authors to clearly identify each sample as being a traditional or mineral formulation. Where mineral samples were present, specific manufacturers could be distinguished.
The literature research available on cosmetics is biased towards lipsticks which are analysed through Raman Spectroscopy. This technique has been proved successful in identifying and differentiating between lipsticks under controlled conditions. But, forensic evidence is not found in these ideal conditions, it is usually on different substrates that have been subjected to environmental conditions. Research into lipsticks as trace evidence is important as it is typically worn by young women who are disproportionately victims of sexual assault Zellner and Quarino (2009).
An early study by Rodger and Broughton (1998) used surface enhanced Raman Spectroscopy to discriminate between five similar lipsticks and evaluated this method for in situ analysis. They smeared lipsticks onto active substrates (glass and cotton) and all samples were analysed at one wavelength (514.5 nm). Due to the high fluorescence reported at this wavelength, they were unable to obtain spectra for many of the samples. To resolve this a silver colloid was added. The authors could then identify some of the individual pigments present and they successfully identified the lipsticks with no background fluorescence from the substrates.
A later study by Salahioglu et al (2013) assessed smears on numerous surfaces, the effects of ageing and the use of chemo-metrics to classify lipstick spectra. They smeared lipstick on
textile fibres, cigarette butts, glass slides and tissues. Similarly to Rodger and Broughton (1998) they successfully differentiated between all lipstick smears with little/no interference from the substrate. Where textile fibres (in the form of threads) were used lipstick traces on various substrates can be differentiated but, fluorescence problems were encountered with the 633 nm wavelength (less than half of the spectra were obtained). They overcome the fluorescence issue by using frequencies of 473 and 784 but, the most successful results reported at 473 nm. Nether the less, all samples were differentiated from each other by using both lasers together. Chemo-metrics characterised 30 spectra from 10 different lipsticks which were analysed by Principal Components Analysis (PCA). The correct classification was achieved on 98.7% of the samples. The effects of ageing was also investigated. Twenty lipsticks were smeared onto a glass slide (left at room temperature) and the spectra was recorded periodically. 15/20 samples were found to give the same spectra when analysed up to two years after the deposition of the sample.
Gardner et al (2013) analysed known samples of lipsticks through Raman Spectroscopy to see if they can be identified through their spectra. 80 samples were analysed using smears on aluminium foil (which has no Raman signal). Cosmetic smears were then smeared onto fabric and other substrates which were analysed in situ. A spectrum of each substrate was obtained for a reference. Samples were measured using two wavelengths (532 and 780 nm) and compared via spectra overlay to determine the favoured wavelength. Some fluorescence was observed at both wavelengths but, useable spectra was obtained for all samples analysed. 76/80 lipsticks differed by one or more peaks and therefore, could be discriminated from one another. The differentiating success rate for the study was 95% and it was evaluated based on one or more Raman peaks.
López et al (2014) assessed lipsticks the possibility of analyzing lipsticks on different surfaces by Confocal Raman Microscopy but, without using the silver colloid proposed by Rodger and Broughton (1998). They aimed to find a wavelength that worked for all surfaces that lipsticks can be found on. Forty- nine different lipsticks were placed under a microscope and analyzed. They evaluated samples at 780 nm where, some fluorescence was observed but, it wasn’t enough to overwhelm the spectra. Any fluorescence present was easily removed by employing a baseline correction. A visual inspection of the spectra showed 30 groups not related with
the brand/colour suggesting that lipstick spectra are quite distinctive to each lipstick.
The Raman spectra of 5 different red lipsticks on 12 different surfaces were comparted to evaluate if they can be linked to their smudges using Raman Spectroscopy even on interfering surfaces. The spectrum of a known lipstick was compared to their respective lipstick smudges spectra. Some surfaces didn’t interfere with the spectrum but other provided several bands to the spectrum making identification difficult (paper/plastic cup). Where this occurred, spectral subtraction took place. The background (plastic cup spectrum) was removed from the first spectrum (lipstick stain on the cup) resulting in a spectrum purely composed of bands from the lipstick. Due to the spectra being distinctive, the visual inspection allowed differentiation of the five smudges even on interfering surfaces.
Applications of Infrared Spectroscopy in Forensics
Paint Analysis
Infrared Spectroscopy is a technique used in the forensic sector to support investigations. It is a successful tool for studying paint samples as it provides structural information about the organic/inorganic components which are present in paint Stuart (2013). Paint evidence is important in burglaries particularly when there is forced entry. If paint chips are large enough, an analyst can show that a specific paint chip came from a certain location by fitted the two pieces together like a jigsaw fit puzzle. Also, during collisions it’s important to compare a paint fragment found on the road or on clothing of a car accident victim with paint samples coming from the suspected car. Or, in hit-and-run cases there may not be any comparative evidence so the identification of the paint components can provide information like the paint type and manufacturer.
Paints can be identified by their physical and chemical properties such as colour, texture and layers. Paints undergo analysis to identify their chemical properties. These include micro-chemical tests for solubility. Then instrumental analysis such as Raman Spectroscopy or FTIR Micro Spectrometry would be carried out on a sample to determine the composition of a sample. This aids in identifying the type of paint and the pigmentation and fillers using in the manufacturing process Fisher and Fisher (2012).
Szafarska et al (2009) compared spectra of unknown paint samples to spectra that have the same base and also, against paint that was expected to contain the same chemical composition.
Preliminary and microscopic examinations will reveal differences in the number/order of layers, colours and thickness in paint samples. Chemical examinations will classify the paint according to the type and reveal minor differences in resin and pigmentation. Gothard (1976) analysed 500 vehicle samples using Microscopic techniques and Infrared Spectrophotometry. He successfully differentiated 496/500 samples. He found the sequence of layer of the paint flakes is important when comparing samples because some cars are re-sprayed/finished. He showed that successful discrimination between different paints of the same colour requires analytical methods for examination of the chemical composition.
Another study discriminated between different automobile paints of the same colour. Sixty paint fragments taken from new and repainted cars were examined under an Optical Microscope for morphological examination. The colour and number of layers visible on the cross- section was observed and the Infrared spectrum of each sample was obtained.
The study showed that Optical Microscopy successfully determines the layer sequence which then, enables differentiation between paint samples. If samples have similar structures then the chemical composition of each layer is taken using Infrared Spectroscopy. This method gives information about the pigments, resins and fillers that are present in each layer. The study differentiate between most of fragments of the same colour by observing the number, colour and chemical composition of each layer. However, problems were encountered when paints from different cars were a similar colour and tint for example, 7 cars were grey and metallic. When observing the cross-section the number of layer only different slight in respect of the colour of particular layer so it was difficult to determine if they were significantly different or not from their morphological compositions. In this case, the IR spectra were obtained for particular layers and the components although, the same kind of resin was present that spectra different slightly from one another Zięba-Palus (1999)
Questioned Documents
Infrared Spectroscopy is a useful tool for investigating questioned documents, including toners, inks and paper. Causin et al (2010) used Infrared Spectroscopy and X-ray diffraction to individuate the most discriminating features of question documents. Different paper types were successfully discriminated between all sheets of paper which can be very important when it comes to question document examinations. For inks and toners it is possible to differentiate the organic binders present. The differences in polymer type, copolymer composition and the presence of additives enables Infrared Spectroscopy can be used to classify toners Stuart (2013). The chemical analysis of writing materials such as inks and toner are used to authenticate or determine the age of a document.
Zięba-Palus and Kunicki (2006) studies the discrimination between inks by Micro-FTIR Spectroscopy, Raman Spectroscopy and XRF. 70 samples of blue and black ballpoint pens and gel inks from different brands were examined. A short text was written onto a plain piece of paper and analyzed. The IR spectra were obtained were compared with those corresponding to the standard dyes received from the ink procedures. IR spectra provided information on the main dyes, resins and oily liquids. Raman Spectroscopy allowed the comparison of ink samples and is a valuable complementary technique to Infrared Spectroscopy. When IR and Raman were unable to differentiate the samples, the elemental composition was determined. X-Ray analysis provided information about the pigments in each sample and enabled discrimination between these ink samples. In total approximately 95% of the blue and black ballpoint pens could be distinguished from Infrared and Raman Spectroscopy. Furthermore, 90% of the gel inks were discriminated depending on the colour of gel. The most successful