A study in relation to the random distribution of four fibre types on clothing (incorporating a review of previous target fibre studies).

A new target fibre study was undertaken building upon eight previous published studies, which are reviewed here. Fifty-eight items of outer clothing, obtained from households across England, were taped and searched for three types of commonly occurring fibres and one less common fibre type. The tapes were examined using a combination of automatic and manual searching. Any fibres similar to the target fibres were removed and examined using microspectrophotometry, comparison microscopy, thin layer chromatography (TLC) and fourier transform infrared spectroscopy (FTIR) where applicable. One polyester fibre, four acrylic fibres and eleven wool fibres were found that matched the three commonly occurring target fibre samples. None of the less common polyester fibres were found. One item had six matching wool fibres and another had the polyester fibre and an acrylic fibre recovered from it. The remaining eight fibres were each recovered from individual items. The results suggest that finding a large number of fibres that match a control is unlikely to happen by chance, which supports the findings of the previous target fibre studies.     

Further insights into the persistence of transferred fibres on outdoor clothes.

This study was conducted to assess persistence of fibres on items of outdoor clothes in normal wear situations. The persistence of acrylic and wool fibres transferred on 23 recipient garments was examined in relation to: time of wear; features of the recipient garment (fibre composition, surface structure and texture); conditions of wear (public transport used or not), and; their location on the recipient. After 8 hours of wear more than 75% of transferred fibres were lost during 8-10 hours of wear. After 16 hours of wear no more than 10%, most often up to 5%, of fibres remained. Fibres were lost at higher rate when public transport was used. The persistence of fibres depended more on the surface structure and texture of the recipient garment and the location of donor fibres rather than on the type of fibre.     

The persistence of human scalp hair on clothing fabrics

This study reports the persistence behaviour of human scalp hairs under a number of different circumstances. The effects of artificial dyeing of hairs, the presence or absence of roots and different types of fabrics on the persistence of hair on a variety of garments were investigated. The garments were made from cotton, polycotton, cotton/acrylic, polyester and wool. The results indicated that neither artificial dyes nor the presence or absence of roots had statistically significant effects on the persistence of hair. In contrast, the type of fabric had a major impact and it was found that, generally, hairs persist longer on rougher fabrics. The rate of loss of hairs from non-woollen fabrics during normal wear was found to follow an exponential decay curve. In contrast, the rate of loss from the woollen garments was quite linear, indicating a constant, even loss, and thus suggests that a different process is involved in the persistence of hairs on woollen garments from that on non-woollen garments. The speed at which hair was lost from fabrics decreased in the order polyester, cotton/acrylic, polycotton, cotton, smooth wool, rough wool, so that wool gives the best chance of recovering samples of hair. Due to the uniqueness of each case, it is advised that caution be used when making any interpretations and before drawing any conclusions.     

Transfer experiments with acrylic fibres

Some simple experiments on the transfer of acrylic fibres simulating real life conditions are described. The transfer to, and persistence of these fibres on clothing and seating and their secondary transfer under different circumstances was investigated. In all instances the donor fibres were from a red cardigan involved in a homicide case. Interpretation of the case work findings was supported by experimental results. Fibres were shown to persist on seats/car seats despite secondary contacts after their original deposition. Caution is advisable when interpreting the transfer of a very low number of recovered fibres. The fibres were also shown to persist on a variety of garments after they had been washed or dry cleaned.     

The population of coloured fibres in human head hair.

In 2002 a population study of textile fibres in human hair was carried out using 26 volunteers in Cambridgeshire, UK. Over 12,000 fibres were recovered from a variety of hair lengths using low adhesive tape and classified according to colour, generic type and fibre length. The results of the study showed that the most common fibre colours were black/grey (48%), blue (29.1%) and red (12.7%), the least common being green, orange/brown and yellow which each accounted for less than 5% of the total. Natural fibres (mainly cotton) were predominant (72.3%) and man-made fibres were considerably less frequent. When colour and generic type were classified together, the most common combinations were black and blue cottons. The least common were the man-made fibre/colour combinations with the most frequent of these accounting for less than 7% of the sample. Fibre loads carried by long hair were found to be significantly less than that carried by short hair. The results of this study are in accordance with previous fibre population studies using other types of recipient surfaces and are likely to be influenced by factors such as seasonal and geographical variation.     

Persistence of transferred fragrance on fabrics for forensic reconstruction applications

It has recently been established that volatile organic compounds (VOCs) successfully transfer between clothing even with a short contact of 10 s, highlighting the potential to use VOCs in forensic reconstruction scenarios, such as sexual assault cases. The mid and low volatility compounds transferred in greater amounts than high volatility compounds. This study presents empirical data addressing the persistence of transferred VOCs on clothing for the first time. A series of experiments were carried out to determine the persistence of VOCs on clothing for time periods of up 4 weeks, on natural and synthetic fibres, and at three different environmental temperatures. The data indicate that the highest VOC amounts are generally obtained for shorter persistence times of up to 1 d. Whilst high volatility compounds were not recovered in sufficient amounts to allow quantification, the four other transferred VOCs were successfully quantified for persistence times of up to 4 weeks. The persistence for mid-volatility compounds follows decay curve trends in line with those previously obtained for fibres, glass and pollen. When comparing the persistence of VOCs on a natural and a synthetic fibre, for a persistence time of 1 h, the transferred VOCs were retained on a natural fibre in higher amounts than on a synthetic fibre. However, for longer persistence times the concentration of VOCs was similar between the two fabrics. Lastly, lower environmental temperatures resulted in higher recoveries for most VOCs, especially for short persistence times. These findings demonstrate that optimal recovery of VOCs from clothing occurs when the fabric is kept at cooler temperatures and analysed soon after the fragrance transfer occurred, although VOC recovery was possible at higher temperatures and after longer persistence times. Given the transfer and persistence characteristics of VOCs from fragrance, there is potential for fragrance to be used as a form of trace in forensic reconstruction approaches.     

The transfer and persistence of automotive carpet fibres on shoe soles

The transfer and persistence of automotive carpet fibres to shoe soles was investigated. It was found that fibres were transferred with the normal activity of a car passenger. Carpet type and shoe sole parameters were significant determinants in the number of fibres that transferred. The average number of fibres was between about one and 33 per sole. Fibres that had been transferred after normal activity only persisted for a few minutes after walking. A survey of the shoe soles of people about to leave their car showed that fibres were usually present. The majority of shoe soles surveyed had less than five fibres with the greatest number of fibres found being 14. The likelihood of finding a large number of fibres on such soles is rare. Fibre composition of automotive carpets showed a high degree of variation. Grey was seen to be a common colour irrespective of the colour of the vehicle body.     

The use of linear dichroism in forensic fibre examinations — Part 6. Validation and practical aspects of MSP-PPL

This paper summarizes the results of previous work on the microscopic observation of linear dichroism found in dyed fibres (polyesters, polyamides, wool, silk, cotton, viscose, acrylics and acetates) and in pigmented fibres as well as the measurements on these fibre classes using microspectrophotometry with plane polarized light (MSP-PPL). The validation of this method is discussed and a practical tool is proposed for comparing fibre traces with control fibres. The limitations and strengths of this method are also revised.     

The kinetics of colour change in textiles and fibres treated with detergent solutions: Part II — Spectrophotometric measurements

The aim of this study was to assess colour variations that occur in several types of textiles and their constituent fibres, resulting from the long-term influence of various laundry detergents. A 14-day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. The spectrophotometric measurement of colour changes in fabric samples and test solutions, as well as the microspectrophotometric analysis of colour changes in single fibres were described. An evaluation of the observed colour changes from a forensic fibre analysis expert's point of view, as well as that of an average user/consumer of the textiles and laundry detergents is also provided.     

The analysis and comparison of blue wool fibre populations found at random on clothing.

Fifty-eight garments were taped and searched for mid to dark blue wool fibres. These were then removed from the tapings, mounted on slides and examined using a high-power microscope (400x). A total of 2,740 blue wool fibres were identified and visible range microspectrophotometry (MSP) was performed on them. Three hundred independent blue wool populations were identified on 56 of the 58 garments searched. The lack of control fibres meant the spectral range of each population was unknown. The number of populations may have been underestimated by grouping together the fibres that had broad single peaks and a lack of distinguishing features in the spectra. Although blue wool is considered to be a common fibre type, 300 unique spectral shapes were identified by the use of microspectrophotometry alone. This demonstrates that the dyes used in the dyeing of blue wool are variable. Showing that many different populations of blue wool occur on a range of garments should ensure that the forensic scientist does not underestimate or understate the strength of evidence in cases where blue wool is found. Hopefully this work will enlighten scientists and enable them to also assess the true value of their findings when other commonly occurring fibres are encountered.     

Dichroism measurements in forensic fibre examination. Part 2 — Dyed polyamide, wool and silk fibres

A number of dyed polyamide, wool and silk samples were examined with plane polarized light on their dichroic behavior by optical light microscopy (OLM) and microspectrophotometry with plane polarized light (MSP-PPL). It was found that most of these acid dyed peptidic fibres possess dichroism, but these are weaker than the effects previously described for polyester fibres. The small effects may be not observed, especially for wool, but these can be measured using MSP-PPL.In the three peptidic fibre classes, for the first time, a so called “inverse dichroism” is observed which appears in the absorption spectra as a hyperchromic effect.     

An investigation into the persistence of textile fibres on buried carcasses

A significant amount of research has been carried out on fibres to aid the forensic scientist in determining the significance of these when found on a victim or suspect. This work has focused on open-air environments, and as such no research has been undertaken to examine the persistence of fibres on bodies in the burial environment.Wool and cotton fibres, known to fluoresce under ultraviolet (UV) light, were transferred onto the skin of four porcine (Sus scrofa) carcasses (two carcasses per fibre type). The number of fibres transferred was recorded from images taken under UV light. The remains were subsequently placed in four burial sites and left interred for 14 days. After this period the carcasses were excavated and lightly brushed down to remove the soil layer that had adhered to the skin. Once again photography under UV light was used to record the number of fibres which persisted on the skin.Results showed that after 14 days, wool and cotton fibres remain on the surface of the buried carcasses. In no circumstance was there a total loss of fibres suggesting that in such scenarios, the likelihood of finding fibres is high but the initial number of fibres transferred would be strongly diminished. This has important implications for both the excavation protocol for buried remains and the subsequent analysis for physical evidence.     

The kinetics of colour change in textiles and fibres treated with detergent solutions: Part I—Colour perception and fluorescence microscopy analysis

The aim of this study was to assess colour changes that occur in several types of commonly available textiles as a result of the long-term effects of various popularly used laundry detergents. A 14 day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. Colour changes were evaluated through the visual comparison of the colour of the textile samples against that of the untreated (control) material.The kinetics of the changes in the colour of the fibres were monitored using fluorescence microscopy (UV excitation filter). The conclusions include an assessment of the observed changes from a fibre analysis expert's point of view, as well as that of an average user/consumer of the products involved.     

Transfer of DNA without contact from used clothing,pillowcases and towels by shaking agitation

DNA is frequently retrieved from commonly used objects or surfaces with no apparent biological stains. This DNA may have come from one or more individuals who directly deposited their DNA, or indirectly transferred the DNA of others, when physically contacting the sampled object or surface. Furthermore, contactless indirect DNA transfer of this ‘touch DNA’ from fabric substrates was recently demonstrated to be possible in a controlled laboratory environment. The circumstances and extent to which this form of contactless DNA transfer occurs are largely unknown. This study investigated indirect DNA transfer without contact by applying a gentle shaking agitation to used clothing, pillowcases and towels, with known usage and history, of 10 volunteers above the collection zone of the secondary surface. DNA transfer frequently occurred and was possible from all three investigated items. It occurred at levels that often produced informative profiles where transferred profiles closely resembled the profiles generated from the primary item. The outcomes of this study contribute to expanding the understanding of indirect DNA transfer without contact. However, this field would benefit from investigating a wider range of agitations and/or item types with various histories of use to determine the level of transfer and its detectability under different conditions.     

Blocks of colour IV: the evidential value of blue and red cotton fibres.

Samples of blue and red cotton fibres were examined using light and fluorescence microscopy as well as UV/VIS microspectrophotometry and fluorescence microspectroscopy. The degree of fluorescence and spectral variation was recorded. Particular attention was paid to the recurrence of certain spectral patterns. The importance of spectral information in the UV range is emphasized again. Colour plays a critical role in the comparison of cotton fibres in forensic sciences. Normally, fibres producing spectral patterns that are frequently seen will tend to have a lower evidential value in criminal cases as the choice of putative sources is theoretically greater and vice versa. Besides black cotton, blue and red cotton fibres are very frequent in fibre casework. The very high discriminating power using a combination of light microscopy, fluorescence microscopy and UV/VIS microspectrophotometry shows that even blue and red cotton fibres can provide excellent evidence when involved in fibre transfer cases.     

The persistence of fibres on skin in an outdoor deposition crime scene scenario

Textile fibres were transferred to a pig skin carcass and their persistence determined at daily intervals for up to a 12 day period during which time the carcass was left outdoors exposed to the prevailing weather conditions and animal activity. In the absence of strong winds and precipitation, the loss of fibres was found to be exponential. Stronger winds and heavier precipitation caused an increase in the rate of loss of fibres. The results of this study showed that the majority of fibres transferred to a body deposited outdoors, can be expected to be lost after the first 2 days, however, none of the experiments performed resulted in a complete loss of fibres, even after 12 days exposure. These persistence characteristics differed from those observed in a similar study using small sections of skin, rather than carcasses.The implications of the results of the present study in relation to the examination of fibre evidence in cases of homicide are discussed.     

Dichroism measurements in forensic fibre examination. Part 4-dyed acrylic and acetate fibres

A number of dyed acrylic and acetate fibre samples were examined with plane polarized light on their dichroic behavior by optical light microscopy (OLM) and microspectrophotometry with plane polarized light (MSP-PPL). It was found that most of these low birefringent fibres possess weak dichroic effects that are very hard to observe with microscopy. However, using MSP-PPL, the linear dichroism could be measured. A comparison between the dichroic effects found for the same disperse dyes on triacetate (TrAc), diacetate (Ac), polyester (PES) and polyamide (PA) shows that the linear dichroism follows the order: PA>PES >TrAc, Ac.     

Investigating the effect photodegradation has on natural fibres at a microscopic level

It is a known fact that when fabric is left exposed to sunlight photodegradation occurs. However, no study has ever looked at the photodegradation that occurs to individual fibre filaments as commonly recovered from a scene of crime. To look at photodegradation of individual fibres, wool and cotton fabric were dyed using CI Acid Red 27 and CI Direct Red 80 respectively at two depths of shade, 0.25% and 2.0% owf. Pieces of fabric and individual fibre samples were then placed in a Light Fastness Q-Sun 1000 Xenon test chamber which simulated exposure to sunlight over two time periods, 64 h (equivalent to one weeks sun exposure) and 128 hrs (equivalent to two weeks sun exposure). The resulting pieces of fabric and fibres where then examined using high power comparison microscopy, as well as graded for colour fading using SDC Grey Scale for Assessing Change in Colour (including half steps). Results show that in both fibre types, photodegradation occurs in all samples, however, the degree of fading is shown to vary within a given fibre population showing it is unpredictable in nature.     

The population,transfer and persistence of fibres on the skin of living subjects

Fibres were transferred to the bare arms of living subjects and their persistence determined at intervals up to 24 h, during which normal daily activity was undertaken. Decay curves showed an initial rapid loss followed by an apparently exponential decay. No target fibres were found to remain after 24 h. The length distribution showed a shift towards shorter fibre lengths and the differential shedding results for a polyester/cotton mixture showed a small bias towards the retention of cotton. The population of coloured fibres on bare skin was classified according to perceived colour, length, generic class and the presence or absence of delustrant.     

A further study of dye batch variation in textile and carpet fibres.

Four sets of acrylic fibre samples were obtained from a company that dyes fabrics for the fashion industry. Between seven and ten different batches of fibres constituted each set. Comparison microscopy, visible and UV range microspectrophotometry and thin layer chromatography (TLC) were used to compare the dyes on each batch of fibres within the sets. Only one of the four sets exhibited variation within the batches. The differences were seen when both microscopical and analytical techniques were used. In addition, two further sets of samples had been obtained from a company that produces carpets for the car industry. The first set consisted of 26 batches of acid dyed orange nylon fibres. The second consisted of 21 batches of acid dyed mustard coloured nylon and direct dyed brown viscose fibres blended together. When the first set was viewed under UV light one batch had more pale orange fibres present and they fluoresced more brightly than the other fibres. This could be due to the blending with a different dye batch of fibre or due to poor dye uptake--the latter being more likely. When tested using visible and UV range microspectrophotometry and TLC, further dye batch variation was not detected. The second set was examined after separating the nylon and viscose fibres from each other. The nylon fibres were indistinguishable when a range of microscopical and analytical techniques were employed; however, the viscose fibres showed dye batch variation when TLC was used.