Science and Justice 50 (2010) 77–85

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Automotive flock and its significance in forensic fibre examinations

Josephine Jones ⁎, Tiernan CoyleContact Traces Ltd, The Centre for Innovation & Enterprise, Begbroke Science Park, Sandy Lane, Yarnton, Oxford, OX5 1PF, UK

⁎ Corresponding author.E-mail address: josephine.jones@ContactTraces.com

1355-0306/$ – see front matter © 2009 Forensic Sciencdoi:10.1016/j.scijus.2009.05.003

a b s t r a c t

a r t i c l e i n f o

Article history:Received 29 April 2009Received in revised form 15 May 2009Accepted 21 May 2009

Keywords:Trace evidenceVehiclesFlockFibresMicroscopyFTIRRamanDiscriminating power

The interiors of fifty eight vehicles were examined and samples were taken. All vehicles had samples offlocked material in their interiors. Flocked material was found on the window channels, window frames, dooredges and in glove compartments or central console compartments. The majority of flock fibres used in thevehicles examined were carbon black pigmented polyester or nylon. A variety of dyed nylon fibres were alsoused in the vehicles. The discrimination power of dyed flock fibres used in the interior of vehicles was foundto be 0.974. The front seats of these vehicles were examined for loose flock fibres. All vehicles had flock fibrespresent on the front seats. In the majority of vehicles, flock originating from material in the vehicle's interiorwas present on the front seats of the vehicle. The number of flock fibres present on the front seats variedgreatly from car to car but did not appear to be dependant on the type of seat fabric or on which areas in thecar were flocked.

© 2009 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

1. Introduction

Over the last few years we have seen an increase in cases involvingmotor vehicles where flock fibres were found to provide an evidentiallink between clothing (from a suspect or victim) and the vehicle inquestion. This seems to occur more often in cases involving vehiclesmanufactured in the last 10 years. Although many studies have beencarried out detailing fibre transfer from vehicles to items of clothingand vice versa [1,2], little known work has been carried out intoexamining the use of flock fibres inside vehicles. This studyinvestigates the types of fibres used in flocked material and alsowhere this material is found in vehicles. Comparisons of flock samplesfrom different vehicles will help to establish the level of discrimina-tion of flock fibres and therefore assist in providing a basis forassessing the evidential significance of finding such fibres in a case.

Flocked material is made by propelling short (0.5–4 mm) mono-filament fibres directly onto a substrate that has been previouslycoated with an adhesive. The process electrically charges the flockfibres, causing them to “stand-up” so that they stick into the adhesiveat right angles to the substrate [3]. In vehicles, some applications offlockedmaterial are in areas where fabric with a soft velvet-like feel isdesirable or where sound insulation is required. Flock may also beproduced as a yarn and woven into textiles. The main application oftextiles wovenwith flocked yarn is for covers of car seats [4]. Since the

(J. Jones).

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fibres adhere to the surfaces of the adhesive, rather than penetrate orimbed in it, fibres are shed readily from the surface of flockedmaterial.

In a study carried out by Roux et al. [2] it was found that manyfibres from the clothing worn by the driver of a vehicle weretransferred to the surfaces of the seat even after a short lived contact.The simple action of sitting on a seat generated transfer of 100–10,000fibres. This number was influenced by the kind of garment and thedriving time. Therefore if there are fibres present on the seats at thetime of contact, either from the seat material itself or a population offibres (e.g flock), then when contact occurs with the seat, these fibresshould be transferred back to the clothing of the recipient. Consideringthe high shedding ability of flockedmaterial it is logical to suggest thatduring normal use of the vehicle these fibres should be continuallydeposited on other surfaces within the interior of the vehicle (e.g thefront seats). If this is the case, there is no reason why flock fibreswould not be transferred back to the recipient clothing, either incontact with the flocked material itself or indirectly via anothersurface (such as a seat) and therefore potentially provide a two-waytransfer of fibres between the interior of the vehicle and the clothingin question.

Wiggins et al. [5] stated: “Whena two-way transfer offibres has beenestablished, there can be little doubt that contact has occurred”. In thatstudy two types of car seat fibres were targeted and looked for on overfifty garments. When targeting a “rare” type of black polyester used inonly one vehicle model for a short period of time, no such fibres werefound at random on the clothes targeted. Only one grey polyester fibrefrom a “common” fabric type was found at random. This suggests thatregardless of the number of potential sources for a particular fibre type,

land Ltd. All rights reserved.

Table 1List of vehicles examined at Oxford Motor Park.

Vehicle no. Manufacturer Model Registration year

1 HONDA CR-V 20082 HONDA CIVIC HYBRID 20083 HONDA CIVIC 20084 HONDA LEGEND 20085 HONDA ACCORD 20086 HONDA S2000 20087 HONDA JAZZ 20038 HONDA CIVIC TYPE R 20049 HONDA CIVIC TYPE R 200510 HONDA CIVIC 200611 FORD FOCUS COUPE CABRIOLET 200812 FORD FOCUS ST 200813 FORD C-MAX 200814 FORD KUGA 2008

78 Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

finding a population of these fibres on someone's clothing is unlikely tooccur by coincidence and depending on the case circumstances can beevidentially significant. If this can be incorporated into a two-waytransfer of fibres then the evidential strength is increased even further.

There is no reason why the same logic cannot be applied to flockfibres used in the interior of vehicles. However further information isrequired before this assumption can be made. The aim of this study isto examine:

• Where flocked material is used.• The types and morphology of flock fibres.• The ability to discriminate between flock fibres from differentsources.

• Whether these flock fibres are present on the front seats of thevehicle.

15 FORD KA 200516 FORD FOCUS 200717 HONDA CR-V 200218 FORD FOCUS 200119 FORD FOCUS ZETEC 200520 FORD GALAXY 200021 TOYOTA AURIS 200822 TOYOTA AVENSIS 200823 TOYOTA PRIUS 200824 TOYOTA RAV4 200825 TOYOTA AYGO 200826 TOYOTA YARIS 200827 TOYOTA VERSO 200828 TOYOTA YARIS 200229 TOYOTA AVENSIS 200430 TOYOTA CELICA 200531 TOYOTA RAV4 200532 TOYOTA COROLLA 200533 VW PHAETON GP 200834 VW SCIROCCO 200835 VW BEETLE CABRIOLET 200836 VW GOLF 200837 VW PASSAT 200838 VW POLO 200839 VW EOS 200840 VW BEETLE CABRIOLET 200541 VW POLO 200642 VW POLO 200743 VW GOLF 200544 VAUXHALL ASTRA 200845 VAUXHALL ANTARA 200846 VAUXHALL ZAFIRA 200847 VAUXHALL VECTRA 200848 VAUXHALL CORSA 200849 VAUXHALL TIGRA 200850 VAUXHALL VECTRA 200451 VAUXHALL CORSA 200352 FORD FIESTA 200453 RENAULT SCENIC 200854 RENAULT LAGUNA 200855 RENAULT TWINGO 200856 RENAULT KOLEOS 200857 RENAULT GRANDE MODUS 200858 RENAULT CLIO SPORT 2008

2. Experimental method

2.1. Sampling of flocked material

Fifty eight motor vehicles from six retailers (Honda, Ford, Toyota,Volkswagen, Vauxhall and Renault) in the Oxford Motor Park,Kidlington, UK were examined for areas of flocked material. Detailsof the vehicles sampled are shown in Table 1. All 2008 registeredmodels were new vehicles in the show rooms and all other modelswere used vehicles on the forecourts.1 Samples were taken from anyvisible areas of flocked material using a low adhesive tape-lift whichwas secured to a clear plastic sheet.

In the laboratory, the samples of flock fibres were examined using aLeica MZ16 stereomicroscope (magnification range ×7.1–115). At leasttwenty fibres from each sampled area were removed from the tapeand mounted on microscope slides in Entellan® under glass cover-slips.

2.2. Background flock levels

In order to record the background levels of flock fibres on the frontseats of the vehicles, the seats were taped using low adhesive tape-lifts. To minimise the time spent searching the tapes and because flockis a relatively easy target to find, only one tape-lift was used per seat.

Each tape was examined for flock fibres using the Leica MZ16stereomicroscope. All flock fibres found were highlighted andcounted. If it was apparent that hundreds of flock fibres were present,only a proportion of these were highlighted and an estimate of thenumber present was made (e.g >500 or >1000). A sample (10–20) ofthe highlighted fibres was mounted in Entellan® for microscopicexamination.

2.3. Microscopic examination

A Leica DM EP polarised light microscope (PLM) was used toexamine the flock fibres at magnifications between ×100 and ×400.Information about the colour, morphology, length, diameter and lustreof the fibres was recorded and the birefringence characteristics wereused to give an initial identification of the fibre type.

A Leica FS 4000 comparisonmicroscopewas used to compare flockfibres under transmitted white light (bright field) and reflectedincident light (equipped with Leica narrow banded excitation filtersUV (A) and Blue (I3)). Flock fibres with similar morphologicalcharacteristics, either from different areas within a vehicle or fromdifferent vehicles, were compared using these methods.

1 As the samples were taken from vehicles in show rooms and on forecourts and notfrom vehicles in normal use, some bias may be present when interpreting the findingsrelating to flock fibres on the front seats.

2.4. Instrumental analysis

The spectral characteristics of the flock fibres were analysed usinga Zeiss/TIDAS Microspectrophotometer (MSP) in the region of380 nm–730 nm. Spectralys software was used to obtain the 1stderivative of the spectra using the Savitzky–Golay algorithm. The MSPspectra (including 1st derivatives) of any flock fibres that were foundto be microscopically indistinguishable were compared. Spectra ofblack pigmented fibres were not taken due to the lack of spectralinformation gained from black pigmented fibres [6].

The chemical composition of the flock fibreswas determined using aThermo Nicolet iN10 Fourier Transform Infra-red (FTIR) spectrometer.

Table 2Where flock is used in the interior of vehicles.

Carno.

Flocked areas

Windowchannel/edge

Dooredge

Glovecompartment

Central consolecompartment

Seatfabric

Doortray

Visor

79Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

Fibreswere flattened using a diamondwindowand placed into the pathof the IR beam. Spectra were obtained over a range of 4000–650 cm−1.

The presence of carbon in the black pigmented flock fibres wasdetermined using a Thermo DXR Smart Raman Microscope using a780 nm laser. Spectra were obtained over a range of 3400–450 cm−1.2

1 ✓ – – – – – –

2 ✓ – – – – – –

3 ✓ – – – – – –

4 ✓ ✓ – – – – –

5 ✓ ✓ – – – – –

6 ✓ – – – – – ✓

7 ✓ – – – – – –

8 ✓ – – – – – –

9 ✓ – – – – – –

10 ✓ – – – – – –

11 ✓ – – – – – –

12 ✓ ✓ – – – – –

13 ✓ – – – – – –

14 ✓ ✓ – – – – –

15 ✓ – – – – – –

16 ✓ ✓ – – – – –

17 ✓ – – – – – –

18 ✓ ✓ – – – – –

3. Results

3.1. Where flocked material is used

All fifty eight vehicles had flocked material in the windowchannels. The majority of the vehicles had flocked window framesor door edges. Fifteen vehicles had flocked glove compartments orcentral console compartments, one vehicle (34 – VW Scirocco) had atray in the door panel lined with flockedmaterial and one vehicle (6 –

Honda S2000) had flocked sun visors. Seat fabric constructed fromwoven flocked yarns was seen in two of the fifty eight vehicles (41 –

VW Polo and 43 – VWGolf). Table 2 details this information and Fig. 1shows examples of where flocked material is used inside vehicles.

19 ✓ ✓ – – – – –

20 ✓ ✓ – – – – –

21 ✓ – – – – – –

22 ✓ – ✓ – – – –

23 ✓ – ✓ – – – –

24 ✓ – ✓ – – – –

25 ✓ – – – – – –

26 ✓ – – – – – –

27 ✓ – – – – – –

28 ✓ – – – – – –

29 ✓ – ✓ – – – –

30 ✓ – – – – – –

31 ✓ – – – – – –

32 ✓ – – – – – –

33 ✓ ✓ ✓ ✓ – – –

34 ✓ – ✓ – – ✓ –

35 ✓ – – – – – –

36 ✓ ✓ ✓ – – – –

37 ✓ – ✓ ✓ – – –

38 ✓ – – – – – –

39 ✓ – ✓ – – – –

40 ✓ – – ✓ – – –

41 ✓ ✓ – – ✓ – –

42 ✓ – – – – – –

43 ✓ – ✓ – ✓ – –

44 ✓ – – – – – –

45 ✓ – ✓ ✓ – – –

46 ✓ – – – – – –

47 ✓ – ✓ – – – –

48 ✓ – – – – – –

49 ✓ – – – – – –

50 ✓ – ✓ – – – –

51 ✓ – – – – – –

52 ✓ – – – – – –

53 ✓ ✓ – – – – –

54 ✓ ✓ ✓ – – – –

55 ✓ – – – – – –

56 ✓ – – – – – –

57 ✓ – – – – – –

58 ✓ – – – – – –

3.2. Types and morphology

3.2.1. Windows and doorsOnly flock fibres that appeared black under the stereomicroscope

(up to 50× magnification) appeared to be used in the window anddoor areas. They were approximately 0.5 mm–1.0 mm in length andhad a diameter of approximately 15–25 µm. Almost all of themappeared to have round cross-sections although, in three vehicles (2 –

Honda Civic Hybrid, 27 – Toyota Verso and 32 – Toyota Corolla) one ortwo flock fibres with a tri-lobal appearance3 were present in thesamples. The majority of flock fibres from the windows and door areaswere carbon black pigmented nylon or polyester. Any dyed flock fibresused in thewindowor door areaswere classed using theirmicroscopicappearance (at >100× magnification) as blue-grey, grey or blacknylon. Table 3 shows the types of flock present in the window anddoor areas of all fifty eight vehicles.

Carbon black pigmented polyester fibres were present in thewindow and door areas of 55% of the vehicles. In twelve cars, the onlysource of flock found in the vehicle was the carbon black polyesterflock from the window and door areas. Seven of these vehicles wereFord models.

Carbon black pigmented nylon (nylon 6,6) was present in thewindow or door areas of 36% of the vehicles. Only in three vehicles (allHonda models), was carbon black nylon from the window and doorareas the sole flock fibre source found in the vehicles.

No attemptwasmade to discriminate the carbon black pigmentedfibres, firstly due to the variation seen in a sample taken from onearea and secondly due to the difficulty in comparison of blackpigmented fibres [6]. It is worth mentioning that the distribution ofcarbon black pigment in the nylon fibres differed greatly from thatseen in the carbon black pigmented polyester fibres, it wasconsiderably finer and as such the fibres appeared brown at highmagnification (Fig. 2).

All blue-grey dyed nylon fibres appeared delustered, although thenumber and size of delustrant particles varied considerably (Fig. 3). Intwelve of the cars, the only source of flock found in the vehicle wasblue-grey nylon flock from the window and door areas. Seven of thesevehicles were Honda models. FTIR spectroscopy of a sample of theblue-grey nylon flock fibres showed that they were either nylon 6 ornylon 6,6. The type of nylon used did not appear to be dependent onthe manufacturer or the registration year (Table 4).

2 Full details available on request.3 Blue-grey nylon 6.

3.2.2. Glove and central console compartmentsThemajority of flockedmaterial from these areas wasmade up of a

mixture of flock types. Fig. 4 shows the appearance (under thestereomicroscope) of flock on the tapings taken from three glovecompartments.

Although the majority of flock fibres from these areas were madefrom nylon, carbon black pigmented polyester was present in twovehicles and black viscose flock4 was noted as a minor component of

4 As only one or two such viscose flock fibres were present in the sample, this wasconsidered to be a very minor component and as such has not been included in Table 5.

Fig. 1. Examples of where flocked material is used inside vehicles (a) Window edge (b) Door edge (c) Glove compartment (d) Window channel.

80 Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

one glove compartment sample (22 – Toyota Avensis). Of the nylonfibres, all appeared to have a round cross-section and had a lengthvarying from 0.5–2.0 mm and a diameter of about 15–25 µm. Carbonblack pigmented nylon fibres were present in compartments fromeleven of the fifteen vehicles and dyed fibres were present incompartments from fourteen of the fifteen vehicles. Most of thedyed flock fibreswere in themicroscopic class of blue-grey or grey, butvarious other colours were present, including brown, green, red,orange and pale yellow. Table 5 shows the types of flock fibres presentin the material lining the glove and central console compartments.

3.2.3. Seat fabricBoth examples of seat fabric with woven flocked yarns comprised

several types of flock fibres. In the VW Polo (41) the fibres weregrouped into the following classes: blue-grey, grey and brown nylon.They all appeared round, were approximately 0.5 mm long and had adiameter of approximately 10 µm. They were notably finer than thosefrom other flocked areas within the vehicles. In the VW Golf (43), thefibres were classed as follows: blue-grey nylon, grey nylon, carbonblack pigmented polyester and blue viscose flock fibres. Apart fromthe viscose, they appeared round, had a diameter of approximately20 µm and were between 0.5 and 1.0 mm long.

3.2.4. Sun visorThe flock fibres from the Honda S2000 (6) sun visors appeared to

be all one type of round, grey dyed nylon with a diameter ofapproximately 15 µm and a length of approximately 1 mm. Ratherthan being straight like the other flock encountered in this study, themajority of themwere kinked. No such flock fibres were noted in anyof the other vehicles.

3.2.5. Chemical compositionThe chemical composition of a sample of the flock fibres was

determined using FTIR spectroscopy. The results of this analysis aredetailed in Table 4. Of the fibres analysed, only nylon 6,6 flock fibreswere present in the glove and central console compartments. Bothnylon 6 and nylon 6,6 dyed fibres were present in the windowchannels. The carbon black pigmented flock fibres were made eitherfrom polyester (windows/doors only) or nylon 6,6. One example of atri-lobal nylon was confirmed to be nylon 6.

3.3. Discrimination of flock fibres

Any dyed fibres that were grouped in the same microscopic classwere compared under different lighting conditions (Fig. 5). If anyfibres were found to be indistinguishable under all three lightingconditions their MSP spectra were compared.

3.3.1. Windows and doorsOf all of the dyed nylon fibres from the samples taken from the

window or door areas there were thirteen pairs of blue-grey nylonflock fibres that were microscopically and chemically indistinguish-able. These pairs are shown in Table 6. The pairs can be split into eightgroups of cars with microscopically and chemically indistinguishableflock fibres: 1,2 and 5; 1,5 and 6; 4 and 32; 6 and 27; 7 and 8; 23 and27; 23 and 54; 29, 30 and 31. Five of the groups contain cars from thesame manufacturer and seven of the groups contain cars fromJapanese manufacturers (Honda and Toyota).

3.3.2. Glove and central console compartmentsOf all the dyed types of nylon flock fibres from the glove and central

console compartments, only four pairs of indistinguishable flock fibres(Table 6) were found. The pairs are 36 and 39 (Grey nylon –VW); 34

Table 3Types of flock present in the window channels, window frames and door edges.

Carno.

Flock types – microscopic appearance

Black pigmentedpolyester

Black pigmentednylon

Blue-greynylon

Greynylon

Blacknylon

1 – – ✓ – –

2 – ✓ ✓a – –

3 – ✓ – – –

4 – – ✓ – –

5 – – ✓ – –

6 – – ✓ – –

7 – – ✓ – –

8 – – ✓ – –

9 – – ✓ – –

10 – ✓ – – –

11 ✓ ✓ – – –

12 ✓ – – – –

13 ✓ – – – –

14 ✓ – – – –

15 ✓ – – – –

16 ✓ – – – –

17 – ✓ – – –

18 ✓ – – – –

19 ✓ – ✓ – –

20 ✓ – – – –

21 – ✓ ✓ – ✓

22 – ✓ – – –

23 – – ✓ – ✓

24 – – ✓ – –

25 – ✓ ✓ – –

26 – ✓ ✓ – –

27 – – ✓a – –

28 – – ✓ – –

29 – ✓ ✓ – –

30 – ✓ ✓ – –

31 – ✓ ✓ – ✓

32 – – ✓a – –

33 ✓ – – – –

34 ✓ – – – –

35 ✓ – ✓ – –

36 ✓ – – – –

37 ✓ – – – –

38 ✓ ✓ – – –

39 ✓ ✓ – ✓ –

40 ✓ – – – –

41 ✓ – – – –

42 ✓ – – – –

43 ✓ – – – –

44 ✓ – – – –

45 – – ✓ – –

46 ✓ ✓ ✓ – –

47 ✓ ✓ – – –

48 ✓ – – – –

49 ✓ – – – –

50 ✓ ✓ – ✓ –

51 ✓ ✓ ✓ – –

52 ✓ – ✓ – –

53 ✓ – – – –

54 – ✓ ✓ – –

55 ✓ ✓ – – –

56 – – ✓ – –

57 ✓ – – – –

58 ✓ ✓ – – –

a Includes one or two tri-lobal fibres.

Fig. 2. Carbon black pigmented nylon flock fibre (x400 magnification).

81Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

and 39 (Grey nylon – VW); 22 and 29 (Black nylon – Toyota) and 34and 36 (Orange nylon – VW). All of these pairs are cars from the samemanufacturers.

Fig. 3. Comparison of blue-grey nylon flock fibres from two Honda vehicles (x400magnification).

3.3.3. Discrimination powerIn total, 662 comparisons of dyed flock fibres were made and only

17 matching pairs were found. This gives the discrimination power ofdyed flock fibres to be 0.974, as calculated according to Grieve andBiermann [7].

3.4. Flock fibres on the front seats

Flock fibres were present on all the seats examined. In 95% of thevehicles examined, flock fibres from areas inside the vehicle werepresent on the front seats. However, the majority of vehicles also had avarietyof otherflockfibres that originated fromunknownsources on thefront seats. Only three vehicles had a significant population (>100) offlockfibres on the front seats that didnot appear to have originated fromthe samples taken from the vehicle. In all three vehicles this populationwas found to consist of black synthetic fibres with the overallappearance of flock, which on closer examination appeared fragmentedor broken rather than cut (Fig. 6). FTIR spectroscopy gave a spectrum ofoxidized polyacrylonitrile (PAN) and Raman micro-spectroscopy iden-tified crystalline carbon. Although the source of these fibres is unknown,research has shown that such “carbon fibres” are used in fire-retardantcushions or fabric in vehicles [8].

The type of fabric used on the seats did not appear to have anyinfluence on the number of flock fibres present on the seats, apartfromwhen the flock originated from the seat fabric itself inwhich casethousands of flock fibres were present. These findings are given inTable 7.

In all vehicles with flocked glove and central console compart-ments flock fibres from both the compartments and the window ordoor areas were present on the front seats. Generally, the presence of aglove compartment does not appear to have a direct effect on thedistribution of flock fibres on the front seats. However, in the ToyotaRAV4 (24) and the Vauxhall Antara (45) there were significantly more

Table 4Chemical composition of flock fibres analysed using FTIR spectroscopy.

Carno.

Window/door areas Glove/central compartments Seatfabric

Blackpigmented

Blue-grey

Blackpigmented

Blue-greyor grey

Black Orange/pale/yellow

Grey/brown

1 – Nylon 6 – – – – –

3 Nylon 6,6b – – – – – –

4 – Nylon 6 – – – – –

7 – Nylon 6,6 – – – – –

9 – Nylon 6 – – – – –

11 Nylon 6,6 – – – – – –

16 Polyester – – – – – –

17 – Nylon 6 – – – – –

19 Polyesterb

21 – Nylon 6 – – – – –

22 – – – Nylon 6,6 Nylon 6,6 – –

23 – – Nylon 6,6 – – – –

24 – Nylon 6,6 – – – – –

25 Nylon 6,6 Nylon 6,6 – – – – –

31 – Nylon 6 – – – – –

32 – Nylon 6a – – – – –

33 – – Nylon 6,6 – – Nylon 6,6 –

35 – Nylon 6,6 – – – – –

38 Nylon 6,6 – – – – – –

40 – – – Nylon 6,6 – – –

41 – – – – – – Nylon 6,643 – – – – – – Nylon 6,644 Polyester – – – – – –

45 – Nylon 6,6 Nylon 6,6 – – – –

47 Nylon 6,6 – – – – – –

50 – – – Nylon 6,6 – – –

54 Nylon 6,6 Nylon 6,6 Nylon 6,6 – Nylon 6,6 Nylon 6,6 –

a Tri-lobal cross-section.b Analysed using Raman spectroscopy – carbon pigment present.

Fig. 4. Flock fibres on tapings (a) Various flock fibres on the taping taken from the glovecompartment of the VW Passat (37) (b) Black pigmented nylon and grey dyed nylonflock fibres on the taping taken from the glove compartment of the Vauxhall Antara(45) (c) Grey dyed nylon flock fibres on the taping taken from the glove compartment ofthe Vauxhall Vectra (50).

82 Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

glove/central console compartment flock fibres on the front nearsideseat than on the driver's seat.5 In the Vauxhall Antara the differencewas particularly obvious, with seven flock fibres on the driver's seatand hundreds of flock fibres on the front nearside seat.

4. Discussion

4.1. Where flocked material is used

Flocked material was present in all vehicles examined and it wasfound in thewindow channels, window frames and door edges as wellas in the glove and central console compartments. Interestingly only26% of vehicles had flocked glove or central console compartmentsand only one example of flocked material in the door panel tray or onthe sun visors was seen. It is also interesting to see examples of flockedfibres used in woven seat fabric, and the number of fibres sheddingfrom the fabric makes it likely that high numbers of these fibres wouldtransfer to the clothing worn by anyone in contact with the fabric. Ifcase examples are seenwhere hundreds of flock fibres of various typesare seen on the seat tapings, it would be recommended that samplesfrom the seat material are obtained.

The same could be said for all other types of flock. Ideally samplesfrom any areas of flocked material should be taken when the vehicle isexamined. They are very easy to take in a non-invasive way with a stripof low adhesive tape.

4.2. Types and morphology

By far the majority of flock fibres from the interior of the vehicleswere synthetic (polyester, nylon 6 or nylon 6,6), round, between 0.5and 2.0 mm long and with a diameter between 10 and 25 µm. The

5 Although both of these vehicles were new cars in the retailer show rooms, extremeexamples of flock distribution like this have also been seen in casework.

majority appeared black under the stereomicroscope, although it doesnot appear to be unusual to see a variety of colours of dyed nylon fibresfrom the flocked material in the glove and central console compart-ments and from the seat fabric. Although very fewof the sampleswerehomogenous with just one type of flock fibre present, the dyed fibreswere surprisingly consistent throughout a sample.

The majority of flock fibres used in the vehicles examined werecarbon black pigmented polyester or nylon. All other flock fibres fromthe window and door areas were dyed nylon with a blue-grey, grey orblack microscopic appearance. Most samples from the glove or centralconsole compartments contained various types of nylon fibres. Themajority were carbon black pigmented nylon but a variety of dyednylon fibres (red, orange, green, brown) were seen that did not appearto be present in the window or door areas.

For the purposes of intelligence, if flock fibres are dyed and theyhave an average length of over 1.0 mm, then the findings would tend

Table 5Types of flock present in glove and central console compartments.

Carno.

Flock types – microscopic appearance

Black pigmented polyester Black pigmented nylon Blue-grey nylon Grey nylon Black nylon Orange nylon Red nylon Green nylon Brown nylon Pale/yellow nylon

22 ✓ ✓ ✓ – ✓ – – – – –

23 – ✓ – – – – – – – –

24 – – – ✓ – – – – – –

29 ✓ ✓ ✓ – ✓ – – – – –

33 – ✓ ✓ – – ✓ – – – ✓

34 – ✓ – ✓ – ✓ – ✓ – –

36 – ✓ – ✓ – ✓ – ✓ – –

37 – ✓ ✓ – – – ✓ ✓ – ✓

39 – ✓ – ✓ – – – – – –

40 – – – ✓ – – – – – –

43 – ✓ ✓ ✓ – – – – ✓ ✓

45 – ✓ – ✓ – – – – – –

47 – – ✓ ✓ – – – – ✓ –

50 – – – ✓ – – – – – –

54 – ✓ ✓ – – – ✓ – – ✓

83Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

to suggest that they originate from the glove or central consolecompartment. If the flock fibres have a diameter under 15 µm it ispossible that they originate from the seat fabric. If so, this may besupported by the presence of very large numbers of fibres on thetapings of all of the seats in the vehicle.

4.3. Discrimination of flock fibres

The majority of flock fibres examined throughout this study werecarbonblackpigmented. Ingeneral,wefindcarbonblackpigmentedflockfibres very hard to discriminate using traditional means. Significantvariation inmorphology (length anddiameter), pigment distribution andfluorescence characteristics made it very difficult to compare individualflock fibres to the samples from the flocked areas. As such we wouldrecommend that a cautious approach be adopted when considering car-bon black pigmented flock as a potential target fibre. However, if these

Fig. 5. Grey nylon flock fibres stuck in adhesive from the glove compartment of the Vauxha(b) Blue (I3) light excitation (c) UV (A) light excitation.

fibres are just one component of the flocked material, they may beevidentially useful in combination with other target fibres.

The discrimination power (0.974) of dyed flock fibres shows thatsignificant variation is seen between different vehicles, even those ofthe same make. The fact that most of the matching pairs come fromthe same manufacturers is not surprising as it is likely thatmanufacturers have strict requirements for their flocked material,perhaps even having a sole supplier of flocked material in whichsimilar flock fibres would be expected to be used. Although thegeneral microscopic appearance of the fibres may be indistinguish-able, analysis by Vis-MSP highlighted once again that the further levelof discrimination given by the 1st derivative is a very useful tool.

4.4. Flock fibres on the front seats

As expected,flockfibres fromareas in the interior of the vehiclewerepresent on the front seats. The number of such fibres varied greatly, but

ll Vectra (50) as viewed using the comparison microscope (a) Transmitted white light

Table 6Pairs of indistinguishable fibres.

Carno.

Manufacturer Year WD orGC

Carno.

Manufacturer Year WD orGC

Fibre type

1 Honda 2008 WD 2 Honda 2008 WD Blue-grey nylon1 Honda 2008 WD 5 Honda 2008 WD Blue-grey nylon1 Honda 2008 WD 6 Honda 2008 WD Blue-grey nylon2 Honda 2008 WD 5 Honda 2008 WD Blue-grey nylon5 Honda 2008 WD 6 Honda 2008 WD Blue-grey nylon4 Honda 2008 WD 32 Toyota 2005 WD Blue-grey nylon6 Honda 2008 WD 27 Toyota 2008 WD Blue-grey nylon7 Honda 2003 WD 8 Honda 2004 WD Blue-grey nylon23 Toyota 2008 WD 27 Toyota 2008 WD Blue-grey nylon23 Toyota 2008 WD 54 Renault 2008 WD Blue-grey nylon29 Toyota 2004 WD 30 Toyota 2005 WD Blue-grey nylon29 Toyota 2004 WD 31 Toyota 2005 WD Blue-grey nylon30 Toyota 2005 WD 31 Toyota 2005 WD Blue-grey nylon36 VW 2008 GC 39 VW 2008 GC Grey nylon34 VW 2008 GC 39 VW 2008 GC Grey nylon22 Toyota 2008 GC 29 Toyota 2004 GC Black nylon34 VW 2008 GC 36 VW 2008 GC Orange nylon

WD – Window and Door area; GC – Glove or Central Console Compartments.

Table 7Flock fibres on the front seats.

Carno.

Seat material No. offlock onFOS

No. offlock onFNS

Overall % matching samplesfrom interior of the vehicle

1 Woven fabric 33 – 402 Vinyl/leather 7 – 863 Synthetic suede-like fabric 26 – 354 Vinyl/leather 29 – 305 Vinyl and woven fabric 5 – 207 Woven fabric and knitted

velvet10 – 40

8 Synthetic suede-like fabric andwoven fabric

19 – 85

9 Synthetic suede-like fabric andwoven fabric

48 – 5

10 Vinyl/leather 3 – 011 Woven fabric 16 – 5012 Woven fabric 44 – 9013 Woven fabric 44 13 5014 Woven fabric 15 – 6715 Vinyl/leather 9 – 2216 Vinyl/leather 0 – –

17 Woven fabric and vinyl 16 – 718 Woven fabric 19 – 1619 Woven fabric 9 – 5620 Woven fabric 55 – 4521 Woven fabric 20 12 4522 Synthetic suede-like fabric and

vinyl109 135 60

23 Vinyl/leather 24 6 7524 Woven fabric 17 120 3525 Synthetic suede-like fabric and

vinyl62 95 35⁎

26 Woven fabric 28 54 0⁎27 Woven fabric 19 13 1028 Knitted velvet 8 14 629 Woven fabric 27 65 5230 Woven fabric 36 27 531 Woven fabric 18 80 4032 Woven fabric 5 2 4333 Vinyl/leather 20 43 7034 Vinyl/leather 8 41 5635 Vinyl/leather 87 94 5036 Woven fabric 14 60 7037 Vinyl/leather 3 95 10038 Woven fabric 15 58 8539 Vinyl/leather 79 91 9540 Woven fabric 21 13 5041 Woven fabric (flocked yarns) 1000 1000 Seat fabric42 Woven fabric 26 24 6043 Woven fabric (flocked yarns) 1000 1000 Seat fabric44 Woven fabric 34 140 8545 Vinyl/leather 7 500 7646 Woven fabric 28 44 6547 Vinyl and woven 6 22 8548 Woven fabric 24 13 5049 Vinyl/leather 4 6 70

84 Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

in many instances there were more than a hundred flock fibres presentandas suchmadeupapopulationoffibres that couldpotentially transferback to the clothing worn by anyone sitting in the seat.

This tends to support the view that if you are inside a vehicle, flockfibres from that vehicle could transfer to your clothing, not only fromdirect contact with the flocked material (e.g when attempting toremove items from the glove compartment) but also from those looseon the surfaces of the seats.

If very large numbers of flock are found on the car seats it can beconsidered that the most likely source of the flock is the interior of thevehicle itself rather than some other unknown source. The largenumber observed can also provide considerable confidence in the useof flock as a target fibre.

However, the number of flock fibres observed on the tapings mayonly be a residue of those that were present on the surface at the pointof contact. Therefore we would recommend that, where possible,rather than assessing the potential for flock to be a target fibre basedon the number of flock fibres present on the seat tapings, samples offlock from the vehicle are obtained at the time of vehicle examination.As flock fibres are particularly easy to search for on clothing, littleeffort is saved by excluding them from the search strategy in caseworkinvolving a vehicle.

5. Conclusion

This study has shown that flock fibres are used routinely in theinterior of new vehicles. It has also shown that flocked material withautomotive applications appears to be made up from specific samples

Fig. 6. Oxidised PAN fibre with a broken appearance (x400 magnification).

50 Woven fabric 19 65 7551 Woven fabric 11 19 1552 Woven fabric 10 6 4453 Woven fabric 18 36 6554 Synthetic suede-like fabric and

vinyl500 500 25⁎

55 Woven fabric 65 47 9056 Woven fabric 7 4 2757 Woven fabric 41 130 7558 Woven fabric 12 21 65

– Not examined; ⁎ Population of oxidized PAN fibre fragments present – source as yetunknown.

of dyed or pigmented fibres. Therefore, there is no reason why thelogic used in cases that deal with fibres from clothing textiles [9]should not be applied to cases involving flock fibres. We wouldstrongly recommend that flock be considered as a target fibre in allcases where links to motor vehicles are involved.

85Josephine Jones, Tiernan Coyle / Science and Justice 50 (2010) 77–85

6. Case example

The following case example is given to highlight the benefit oflooking for flock fibres on clothing in a case involving motor vehicles.

Two vehicles were stolen during separate burglaries. Thesevehicles were seen together on CCTV. Vehicle A appeared to havethree occupants and vehicle B had two occupants. Vehicle A wasabandoned and it was thought that the three occupants got into therear of vehicle B.

Clothing was seized from all suspects within a few hours of thealleged offence. Clothing from the three suspects thought to beoccupants of vehicle A were examined. All of the clothing had smoothouter surfaces that did not shed fibres. Examination of the tapingsfrom the seats of vehicle A highlighted a population (100's) of greynylon flock fibres on the seats. Between 30 and 150 such flock fibreswere found on the clothing worn by each of the three suspects.Examination of the tapings from the seats of vehicle B showed onesuch flock fibre on the front seats and about 40 on the rear nearsideseat.

The findings were in keeping with the suspects all having been inrecent direct contact with the interior of vehicle A, whereby the likely

explanation is that fibres were transferred to the rear seat of vehicle Bindirectly via their clothing.

This case shows the value of flock as a target fibre particularly in acase where the clothing did not shed fibres. It highlights, once again,the importance of fibre recovery on clothing regardless of the type ofoffence.

References

[1] M.C. Grieve, Back to the future – 40 years of fibre examinations in forensic science,Science & Justice 40 (2) (2000) 93–99.

[2] C. Roux, J. Chable, P. Margot, Fibre transfer experiments onto car seats, Science &Justice 36 (3) (1996) 143–151.

[3] http://www.swicofil.com/flock.html[4] http://www.technovaitalia.it/english/english/prodotto.html[5] K. Wiggins, P. Drummond, T. Hicks Champod, A study in relation to the random

distribution of four fibre types on clothing, Science & Justice 44 (3) (2004) 141–148.[6] M.C. Grieve, S. Deck, Black cellulosic fibres – a “bete noire”? Science & Justice 42 (2)

(2002) 81–88.[7] T.W. Biermann, Blocks of colour IV: the evidential value of blue and red cotton

fibres, Science & Justice 47 (2007) 68–87.[8] http://www.sglgroup.com[9] M.C. Grieve, T.W. Biermann, K. Schaub, The individuality of fibres used to provide

forensic evidence – not all blue polyesters are the same, Science & Justice 45 (1)(2005) 13–28.