The transfer and persistence of automotive carpet fibres on shoe soles

SCIENTIFIC & TECHNICAL

The transfer and persistence of automotive carpet fibres on shoe soles C ROUX and S LANGDON Department of Chemistry, Materials and Forensic Science, University of Technology Sydney, P.O. Box 123, Broadway NSW 2007, Australia D WAIGHT Division of Analytical Laboratories, Institute of Clinical Pathology and Medical Research, Western Sydney Area Health Service, P.O. Box 162, Lidcombe NSW 2141, Australia J ROBERTSON

Forensic Services, Australian Federal Police, GPO Box 401, Canberra ACT 2601, Australia Science & Justice 1999; 39: 239-251 Received 1 October 1998; accepted 17 May 1999 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.

Der Transfer und die Verweildauer von automobilen Teppichfasern auf Schuhsohlen wurde untersucht. Die Ergebnisse zeigen, dass durch normale Benutzung eines Pkw an den Schuhsohlen der Fahrgaste Fasern angetragen werden. Die Teppichart und die Schuhsohlenparameter beeinflussten in signifikanter Weise die Anzahl der iibertragenen Fasern. Die mittlere Anzahl lag zwischen 1 und 33 Exemplaren pro Sohle. Durch normale Benutzung eines Pkw's angetragene Fasern verblieben wahrend des anschliel3enden Gehens nur wenige Minuten auf den Sohlen. Stichproben zeigten bei Personen, die gerade aus dem Auto ausstiegen, dass auf deren Schuhsohlen gewohnlich Fasern nachzuweisen waren. Es waren bei der Mehrheit der untersuchten Schuhsohlen weniger als 5 Fasern nachzuweisen. Die hochste dabei festgestellte Anzahl belief sich auf 14 Faserexemplare. Die Wahrscheinlichkeit ist gering, eine grol3e Fasermenge auf solchen Sohlen zu finden. Die Faserzusammensetzung automobiler Teppiche besitzt einen hohen Grad an Variation. Unabhagig von der Wagenfarbe war die Farbe Grau bei automobilen Teppichen oft anzutreffen.

Le transfert et la persistance de fibres de tapis d'automobiles sur les semelles de chaussures ont CtC CtudiCs. Les fibres sont transfCrCes lors d'une activitC normale d'un passager d'une voiture. Les types de tapis et de semelles de chaussures constituent des paramktres significatifs et determinants dans le nombre de fibres transfCrCes par semelle. Les fibres ainsi transfkrkes aprks une activitC normale ne restent que quelques minutes aprks une activitC de marche. Un sondage des semelles de chaussures de personnes qui vont quitter leur voiture a montrC que des fibres Ctaient habituellement prCsentes. La majorit6 des semelles sondCes prksentaient moins de cinq fibres avec le plus grand nombre de fibres trouvCes Ctant quatorze. Le risque de trouver un grand nombre de fibres sur des semelles est rare. La composition en fibres des tapis automobiles a montrC un haut degrC de variation. Le gris est une couleur commune indkpendamment de la couleur de la carrosserie du vChicule.

Se investig6 la transferencia y persistencia de fibras de alfombrillas de coches a la suela de zapatos. Se encontr6 que las fibras son transferidas en la actividad normal de un pasajero de coche. El tip0 de alfombrilla y 10s partimetros de la suela del zapato eran determinantes significativos en el numero de fibras transferidas. El n6mero medio de fibras transferidas era entre 1 y 33 por suela. Las fibras que habian sido transferidas en la actividad normal s610 persistian unos pocos minutos despuCs de andar. Un estudio de las suelas de zapato de la gente a punto de abandonar su coche mostr6 que las fibras estiin habitualmente presentes. La mayoria de las suelas de zapato estudiadas tenian menos de cinco fibras, encontriindose un miiximo de catorce fibras. La probabilidad de encontrar un gran numero de fibras en las suelas, es rara. La composicidn de alfombrillas de coche mostraba un alto grado de variacibn. Se encontr6 que el gris era un color bastante com6n en las fibras, independientemente del color del coche.

Key Words: Forensic science; Criminalistics; Fibre evidence; Transfer; Persistence; Automotive carpet; Shoe. Science & Justice 1999; 39(4):239-251

239

The transfer and persistence of automotive carpet fibres on shoe soles

Introduction Fibres are often investigated in forensic science as they are a form of evidence that obeys Locard's Exchange principle, that is, every contact leaves a trace [I]. A perpetrator of a crime will often leave fibres behind at the scene, on an object or on a victim. The most common example of fibre transfer, and also the most studied [2-61, is where fibres are transferred from clothing to clothing. However, there exists a more obvious, but often overlooked, type of contact in our daily activities which potentially involves fibre transfer: the contact between shoe soles and carpets. This assumption is not merely theoretical and has a real practical significance, as shown by a recent Australian case where a murder victim was found with a relatively large number of three types of synthetic fibres on the shoe soles. Apart from the shoe soles, these fibres were not found on any other item of the victim's clothing. Furthermore, the victim's clothing was eliminated as a possible source of these fibres. Fibres from samples of carpets originating from various sources were examined, and it was found that the carpet of a car belonging to a suspect, was composed of three fibre types indistinguishable from those found on the victim. A number of questions emerge from this case which have more general significance for fibre evidence in such circumstances. Can automotive carpet fibres be transferred to shoe soles during normal activity, and if so how many can be expected? How long will transferred fibres persist on shoe soles? What are the significant parameters in determining the number of fibres that transfer? How many fibres would be expected on the "normal" population of shoe soles? What fibres are found in automotive carpet constructions in Australia? Unfortunately, these questions are not covered by the literature and there is no relevant information for Australia. There has only been one study investigating the transfer of carpet fibres to shoe sole material [7] and one on the transfer of car carpet fibres to clothing [S]. To the best of the authors' knowledge no study has been published on the transfer and persistence of automotive carpet fibres on shoe soles. The aim of the present study was to gather experimental data about the transfer and persistence of fibres involving car carpetlshoe sole contacts in order to evaluate the significance of fibre evidence in such circumstances. In addition, information was sought about the natural occurrence of extraneous fibres on shoe soles and about the frequency of fibre types and combinations in automotive carpets. A detailed consideration of the case which prompted this study will be presented in a future paper.

Materials and Methods Transfer of automotive carpetfibres to shoe soles The transfer experiments were designed to simulate real life situations [9]. Whole shoe soles or soles attached to a real

shoe were worn by the experimenter while sitting in a car. Four shoes were used as recipients in the transfer experiments and each pair of shoes was worn in each car (Table 1, Figures 1 4 ) . Since it was not possible to purchase Shoe 4 of the size worn by the experimenter (this make and model of shoes was no longer in production), soles were attached to another pair of shoes by strong double-sided adhesive tape so that they could be worn as normal shoes. The make up and the pattern of the sole were of the same type as those on the shoes relating to the previously mentioned case. Shoes 1 , 2 and 3 were relatively new shoes that had only been worn a few times. As Shoe 4 was constructed from unused soles, sandpaper was used to gently remove any sharp edges and to wear the soles to a similar visual extent as the other shoes. The hardness of the soles of the four shoes used in the transfer experiments and the damaged sole used in the persistence experiment (see below) were measured using a Laboratory Shore A Durometer (ACM Laboratory Pty. Ltd. Victoria, Australia). Ten measurements were taken of each shoe sole at different positions on the sole. These were then averaged. Another pair of shoe soles similar to the case soles were measured for hardness and then left outdoors in an open area for 24 hours where the daytime temperatures were in the mid to high 20°C. The hardness was measured again and compared to the original measurements. Five cars were used for the transfer experiments, including the actual car involved in the case [Table 21. Before each experiment the soles of the shoes were carefully cleaned with a soft brush and visually checked using a magnifying glass. The soles were then brought into contact with the carpet of each car. Feet were moved around to simulate normal movement without vigorous rubbing on the carpet. After five minutes, the number of fibres that had transferred to the shoe soles were counted, with the aid of a magnifying lens and a bright light source, and their positions marked on a diagram. The soles were then cleaned with the brush, visually checked, and the procedure repeated. This procedure was carried out five times. The entire procedure was then replicated with a contact period of 30 minutes. This was carried out for each of the four shoes in each of the five cars. In all cases, the experimenter sat in the front passenger side of each vehicle. The transfer experiments results were tested using a threeway analysis of variance to compare the four soles, five cars and two time periods (five minutes vs. 30 minutes). Effect of additional parameters on the fibre transfer The effect of additional parameters (presence of car mat, violent braking and shoe sole hardness) on the fibre transfer was also investigated. Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAlGHT and J ROBERTSON

TABLE 1 Shoes used as recipients. Shoe

Profile

Description

Sole composition

Manufacturer

1

Low

Ladies court shoe

Natural rubber

Target

2

Medium

Ladies casual loafer

Thermoplastic rubber

Windsor Smith (Lipstick label)

3

Rough

Ladies fashion boot

Thermoplastic rubber

Windsor Smith (Lipstick label)

4

Rough

Shoe sole similar to Thermoplastic rubber those found on the victim

Windsor Smith (Lipstick label)

FIGURE 1 Low vrofde sole (shoe 1).

FIGURE 2 Medium vrofile sole (shoe 2).

FIGURE 3 Rough profile sole (shoe 3).

FIGURE 4 Rough profde sole similar to those found on the victim (shoe 4).

TABLE 2 Details of cars and their carpets used as donors in the experiments. Model

Carpet colour

Fibre composition

Sheddability ( 1 to 5 )

Car

Year

Make

1

1997

Toyota

Rav 4

Grey

Polyester

4

2

1997

Ford

Fairlane

Grey

Polypropylene

4

3

1987

Mitsubishi

Magna

Blue

Polypropylene

1

4

1989

Toyota

Supra

Grey

Nylon 6.6

3

5*

1991

Honda

CRX

Grey

Polypropylene and polyester

4

* Car 5 was the car involved in the police investigation Science & Justice 1999; 39(4): 239-251

24 1

The transfer and persistence of automotive carpet fibres on shoe soles

TABLE 3 Car carpets used for the additional experiments. Carpet

Description

Carpet colour

Fibre composition

Sheddability ( 1 to 5 )

1

Thick pile carpet

Maroon

Polypropylene

5

2

Short pile carpet

Brown

Polypropylene

2

3

Thick pile carpet

Blue

Polypropylene

4

4

- -

Medium pile carpet -

-

. .

- --

-

Polyester

Grey .

-

The car mat in the case was placed in the front passenger footwell of Car 5. The damaged soles from the persistence experiments (profile similar to Shoe 4, see below) were worn for 15 minutes in the front passenger seat and moved to simulate normal activity.After 15 minutes, the number of fibres were counted and marked on a diagram. This procedure was repeated three times, the sole being cleaned between each trial.

In the second persistence experiment, a large number of fibres were transferred to the worn sole by vigorously scuffing the soles over the carpet of the front passenger side of Car 5 for a few minutes. After the fibres had been transferred, the soles and fibres were photographed. The soles were then worn for thirty minutes, while walking over various surfaces. After the thirty minutes, any remaining fibres were noted and photographed.

The soles of Shoe 4 were worn by the experimenter while sitting in the front passenger seat, with both feet placed flat on the floor (without car mats). Car 5 was driven to a speed of approximately 80krnlh and the brakes were suddenly applied. The sudden braking was the only cause of movement. The wearer applied no extra pressure. The number of fibres transferred to the shoe soles were counted and their positions marked on a diagram. The procedure was repeated five times. This entire procedure was then replicated with the car mats in place.

Additional Transfer and Persistence Experiments Other parameters such as wearer of the shoe soles, the presence of marks or impressions on the soles and presence of sticky residue on the soles were investigated. An additional series of transfer and persistence experiments was set up involving four car carpets obtained from car importers and up to nine experimenters wearing the Shoe soles 4. The carpets used for this section are presented in Table 3.

Persistence of automotive carpet3bres transferred on shoe soles The persistence of automotive carpet on shoe soles was investigated by two types of experiments.

In the first experiment, two pairs of soles of the same type as the victim's shoes were used. The first of these was that used as Shoe 4 in the transfer experiments. The second pair of soles (same as Shoe 4) were vigorously scuffed on asphalt and concrete to damage the sole. These two pairs of soles allowed a contrast between the soles of new shoes, that had only been worn a few times, and the soles of well worn shoes. These soles were then attached to a pair of shoes with Velcro. Fibres were transferred to both pairs of soles in two ways. The first was with normal activity in the front passenger side of Car 5 for 15 minutes. The second used vigorous activity for 30 seconds. The number of fibres transferred bv both techniaues were counted. marked on a diagram and photographed. After each type of transfer activity, each pair of shoe sole was worn for five minutes, while walking over three different groups of surfaces, as follows: vinyl and carpet (indoor); concrete and grass (grass areas and footpaths); asphalt (road and car park). After five minutes, any remaining fibres were noted and photographed. 242

Effect of the wearer The test shoe soles were attached to the experimenter's shoes using Velcro as described previously. The soles were rubbed against one of the carpets in ten vigorous backward and forward movements. The fibres which were transferred were counted after the subject walked for five minutes on vinyl and concrete surfaces. The location of the fibres on the shoes was noted. The experiment was repeated with the four carpets and nine different experimenters. Effect of marks and impressions Fibres were transferred to the shoes as above using Carpet A. The soles were then each rubbed on a rubber stool pad which had a ribbed surface. The fibres which were transferred were counted and attention was paid to their possible fusion into the sole material. A five minutes walk was then taken on vinyl and concrete surfaces before counting the remaining fibres as previously described. The experiment was repeated with seven different experimenters. .

_

Effect of a sticky substance on the soles After the soles were cleaned the experimenter stepped into a tray containing Coca Cola for several seconds. The sticky substance was dried partially with a hair drier and then ten vigorous backward and forward movements were made on Carpet A. The transferred fibres were counted in the usual manner. The shoes were then walked in for five minutes on vinyl and concrete surfaces before counting the remaining Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAIGHT and J ROBERTSON

FIGURE 5 Average number of fibres (N=5) transferred from each carpet to low profile soles. left W right

FIGURE 6 Average number of fibres (N=5) transferred from each carpet to medium profile soles. left W right

FIGURE 7 Average number of fibres (N=5) transferred from each carpet to rough profile soles. left W right

FIGURE 8 Average number of fibres (N=5) transferred from each carpet to case profile (rough) soles. left W right

fibres as described previously. The experiment was repeated with nine different experimenters.

placed on an overhead transparency. The density of fibres on the tapes were visually compared and then arbitrarily categorised into five ranked groups, from 1 (low sheddability) to 5 (high sheddability).

Occurrence of automotive carpet fibres A questionnaire was completed by drivers and passengers at the end of a car journey and before they had left their car. Participants were asked to record the number of car carpet fibres on their shoe soles, if any, the length of journey, the make, model and year of manufacture of the car, the colour of the car carpet and if car mats were present. Questionnaires were distributed to: people as they were parking their cars in selected car parks and their shoes were examined while they completed the questionnaire; and also to forensic science students to be completed by them when they next travelled in a car. Participants were asked to pull a fibre sample from their car carpet to compare with the fibres found on their shoe soles. Fibre samples were lifted from the carpets of 40 different cars involved in the frequency survey using clear adhesive tape. A length of tape, approximately 10 cm by 5 cm, was applied to the carpet of the car and pressed down with a moderate force. The tape was then lifted from the carpet and Science & Justice 1999; 39(4): 239-251

Frequency of the Combination of Fibres The fibres in the case study comprised grey polypropylene, blue polypropylene and black polyester. Automotive carpet samples from 175 cars were obtained from all major car importers, including 29 from cars of Honda manufacture. These samples were examined under a low power stereo microscope (6 to 40x) in order to determine whether or not they were similar to the evidential fibres. Samples which remained not discriminated at this stage were then examined by Fourier Transform Infrared Microscopy. Additional statistics were also obtained such as the commonness of some colours and how many fibre types were present in the carpets. Data on these samples are shown in Table 4.

Results and discussion Transfer of Automotive Carpet Fibres to Shoe Soles The results of these transfer experiments offer some support for the findings of Scott [8] where fewer fibres were shed 243

The transfer and persistence of automotive carpetfibres on shoe soles

TABLE 4 Cars surveyed to assess the frequency of the combination of fibres. -. Ref Year Make & Model ---

--

- --

1995 Audi A4 1969 Austin 1800 Mk I1

Carpet colour -

Fibre colour

Fibre cross section

Make & Model

Carpet colour

Fibre colour

Fibre cross section

-

2 x grey 1 x light blue 1 x grey purplelblack 1 x black 1973 Chrysler Valiant 1976 Chrysler Gallant dark brown 1 x dark 1 x brown dark brown 1 x brown 1988 Daihatsu Charade 2 x greyblack 1991 Daihatsu Applause grey 1 x clear 1 x grey 1979 Datsun Stanza dark grey 1 x blueblack 1 x black greyblack 1980 Datsun 200B brown 1 x brown 1980 Datsun 200B 1 x black bluelgrey 1983 Datsun Pulsar 1 x blue 2 x brown 1970 Ford Fairlane brown 1974 Ford Falcon XB dark brown 1 x redbrown 1 x grey 1977 Ford Fairlane light brown 1 x light brown 1 x light grey light grey 1981 Ford Falcon XD 1982 Ford Falcon XE 1 x brown brown 1 x brown 1983 Ford Telstar Ghia brown 1 x brown 1984 Ford Falcon XF brown 1 x clear 2 x brown 1984 Ford Laser brown 2 x maroon 1984 Ford Telstar maroon 1985 Ford Fairmont Ghia grey 1 x black 1 x grey 1 x clear light brown 1 x light brown 1985 Ford Telstar 2 x brown brown 1986 Ford Laser 2 x grey 1986 Ford Laser grey brown 1 x brown 1986 Ford Telstar 1 x grey 1986 Ford Telstar TX5 grey dark brown 1 x brown 1987 Ford Laser 2 x grey dark grey 1988 Ford Laser Ghia 1 x light blue 1988 Ford Telstar grey 1 x blue 2 x grey 2 x grey 1989 Ford Laser grey 1989 Ford Laser Ghia 1 x grey grey 1989 Ford Laser GL 1 x grey grey 2 x grey 1990 Ford Laser grey 1990 Ford Laser Ghia 1 x grey grey 2 x grey 1990 Ford Laser GL grey l x grey 1990 Ford Laser GL grey 1991 Ford Laser 1 x grey grey 2 x grey 1991 Ford Laser L'wire grey 1 x grey 1992 Ford Falcon grey 1994 Ford Falcon 1 x grey grey 1994 Ford Laser 1 x grey grey 1995 Ford Falcon EF 1 x grey grey 1995 Ford Falcon GLi 1 x grey grey 1 x grey 1995 Ford Falcon GLi grey 1 x grey 1995 Ford Laser LX 1 grey 1 x grey 1 x dark grey 1967 Holden Premier greyblack 1984 Holden Berlina dark brown 1 x brown 1986 Holden Barina blue 2 x blue 1986 Holden Commodore light blue 1 x blue 1 x clear 1988 Holden Commodore dark brown 1 x brown 1 x dark grey 1 x grey 1990 Holden 1 x clear 1 x grey 1990 Holden Calais I x clear 1 x grey 1990 Holden Nova 1991 Holden Apollo 1 x light blue 1 x grey 1 x clear 244

Ref Year

1 x black R 1 x clear R 1993 Holden Commodore grey 2 x grey T 1 x clear T 2 x grey T 56 1993 Holden Commodore grey 1 x clear T 57 1994 Holden Commodore grey 1 x grey T 2 x grey T 58 1994 Holden Commodore grey 59 1995 Holden Commodore grey 1 x grey T 60 1995 Holden Commodore bluelgrey 1 x grey T 6 1 1996 Holden Commodore VS grey 1 x grey T 1 x clear T 62 n/a Honda Civic Hatch grey 1 x grey R 1 x pink R 3 x grey R 63 1987 Honda CRX grey 64 1988 Honda Accord grey 1 x bluelgrey T 1 x clear 65 1988 Honda Civic GL grey R 1 x grey R 1 x clear R 66 1988 Honda Civic GL 1 x grey R 67 1988 Honda Civic Hatch 2 x grey R 1 x pink R 1 x light brown T brown 68 1988 Honda Legend 69 1989 Honda Accord greybrown 1 x brownish T 70 1989 Honda Civic Hatch 1 x grey R grey 1 x clear T 71 1989 Honda Concerto grey 1 x bluelgrey T 72 1989 Honda Integra Hatch grey 1 x bluelgrey T 73 1990 Honda Accord greybrown 1 x brownish T 74 1990 Honda Civic GL greybrown 1 x brownish T 75 1990 Honda Legend greybrown 1 x brownish T 1 x blue R 76 1991 Honda Civic GL grey 1 x grey R 1 61ak R greybrown 1 x brownish T 77 1992 Honda Aerodeck 78 1992 Honda CRX grey 3 x grey R - 2 x 61aik R 79 1992 Honda CRX grey 2 x grey R 1 x black R grey 2 x grey R 80 1992 Honda CRX 1 x black R grey 1 x grey T 8 1 1994 Honda Accord 82 1994 Honda Civic GL grey 1 x grey R 83 1994 Honda Legend brown 1 x light brown T grey 1 x grey T 84 1995 Honda Accord 85 1995 Honda Civic GL grey 1 x grey R 86 1995 Honda Civic Hatch grey 1 x grey R 87 1995 Honda CRX grey 2 x grey R 1 x black R 88 1995 Honda CRX grey 2 x grey R 1 x black R 89 1995 Honda Prelude grey 1 x grey R 90 1995 Honda Prelude grey 1 x grey R 1 x black R 91 1990 Hyundai Sonata grey 1 x grey T 92 1995 Hyundai Lantra grey 1 x grey T black 1 x black T 93 1981 Mazda 323 94 1981 Mazda323 brown 1 x brown T 95 1982 Mazda323 dark brown 1 x brown T 96 1982 Mazda 323 Deluxe grey 1 x grey T 97 1984 Mazda 626 dark blue 1 x blue T 98 1985 Mazda 626 dark blue 1 x dark blue T 99 1987 Mazda 626 grey 1 x bluelgrey T 100 1988 Mazda 929 grey 1 x grey T 101 1990 Mazda 626 brown 1 x brown T 102 1993 Mazda 121 grey 1 x grey T 103 1993 Mazda 626 grey 1 x grey R 1 x clear R 104 1994 Mazda MX5 grey 1 x dark grey R 105 1981 MitsubishiExpress L300 light brown 2 x black R 2 x clear R

R 54

1992 Holden Barina

dark grey

R R 55

P R R R R R R P R R

R R P P R R R R T R R R T T R R T T T R T R T R R R T T T T T T T T T T T T T T R R T T T R T T T T T T T T T T T T

Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAIGHT and J ROBERTSON

TABLE 4 Cars surveyed to assess the frequency of the combination of fibres. Ref Year Make & Model

Carpet colour

Fibre colour

Fibre cross section

Ref Year

Make & Model

Carpet colour

-

106 107 108 109

1985 1985 1988 1990

Mitsubishi Magna Mitsubishi Magna Mitsubishi Pajero Mitsubishi Gallant

brown dark brown grey grey

110 1990 Mitsubishi Magna grey 111 1990 Mitsubishi Magna SW dark blue 112 1992 Mitsubishi Magna dark grey 113 1994 Mitsubishi Magna T5 grey 114 1995 Mitsubishi Magna bluelgrey 115 116 117 118

1993 1959 1978 1988

Mitsubushi Lancer Moms Minor 1000 Nissan Skyline Nissan Skyline GXE

grey light grey light brown grey

119 1989 Nissan Pulsar

brown

120 1990 Nissan Pulsar

grey

121 1990 Nissan Victor

dark grey

122 1992 Nissan Maxima TI 123 1992 Nissan Pulsar

dark grey grey

124 1992 Nissan Pulsar Q 125 1993 Nissan 4WD

dark grey

126 127 128 129

brown grey grey dark brown

1981 1981 1986 1981

Rover Range Sigma GL Sigma GL Subaru Leone

130 1984 Subaru T.Wagon 131 1990 Subaru Liberty 132 1989 Suzuki Swift 133 1991 Suzuki Swift 134 1991 Suzuki Vitara JLX 135 1992 Suzuki Vitara 136 1993 Suzuki Swift

grey grey dark grey

137 138 139 140 141 142

brown brown dark brown grey brown blue

1974 1976 1978 1979 1982 1982

Toyota Crown Toyota Corona MkII Toyota Corona SW Toyota Corona Toyota Crown Royal Toyota T-18 Hatch

143 1983 Toyota Corolla CS 144 1983 Toyota Corona CS

light brown brown

Science & Justice 1999; 39(4): 239-251

1 x brown R 1 x dark brown T 1 x blue R 1 x blue R 1 x grey T 1 x grey R 1 x blue R 1 x black R 2 x grey R 2 x grey R 1 x blue R 1 x black R 1 x dark grey R 1 x light grey R 1 x light brown T 1 x black R 1 x grey R 1 x clear R 1 x black R 1 x brown R 1 x black R 1 x brown R 1 x grey R 1 x black R 1 x grey R 1 x clear R 1 x dark grey T 1 x clear R 1 x grey R 1 x grey R 1 x clear R 1 x purple1blackR 1 x clear R 1 x brown P I x bluelgrey R 1 x grey R 2 x maroon R 2 x clear R 1 x grey T 1 x grey T 1 x grey R 1 x black R 1 x clear R 1 x grey R 1 x blue R 1 x grey R 1 x grey R 1 x black R 1 x clear R 1 x brown R 1 x brown T 2 x brown R 1 x grey R 1 x brown T 2 x blue R 2 x dark blue R 1 x clear R 1 x light brown R 1 x light brown R 1 x brown R 1 x maroon R

Fibre colour --

145 1984 Toyota Corolla

brown

146 1984 Toyota Corolla CSX

brown

147 1985 Toyota Corolla 148 1985 Toyota Corolla Seca 149 1985 Toyota Corona 150 1986 Toyota Celica 151 1986 Toyota Corolla

dark grey dark brown

152 1986 Toyota Corolla 153 1988 Toyota Corolla Seca 154 1989 Toyota Camry

dark brown

155 1989 Toyota Lexcen 156 157 158 159 160 161 162 163

1990 1990 1990 1990 1990 1990 1990 1990

Toyota Celica Toyota Corolla Toyota Corolla Toyota Corolla Toyota Corolla Seca Toyota Corolla Seca Toyota Cressida Toyota Tarago

grey black grey grey dark grey grey bluelgrey grey

164 1991 Toyota Camry 165 1991 Toyota Camry 166 1991 Toyota MR2 167 1992 Toyota Camry 168 1993 Toyota Camry 169 1993 Toyota Corolla Seca 170 1994 Toyota Carnry 171 1994 Toyota Corolla Seca 172 1995 Toyota Camry 173 1995 Toyota Camry 174 1995 Toyota Carnry 175 1978 Volvo 245L R T P FR RT

=

= = = =

essentially circular trilobal peanut shaped flat ribbon roundish trilobal

dark grey

Fibre cross section --

1 x light brown T 1 x dark brown T 1 x light brown R 1 x brown R 1 x maroon R 1 x grey T 1 x grey T I x black R 1 x clear R 1 x grey T 1 x brown T I x black T 1 x grey T 1 x grey T 1 x clear T 1 x light brown T 1 x dark brown T 1 x black RT 1 x grey RT 1 x grey T I x black R 1 x grey T 1 x grey T 1 x dark grey T T 1 x grey 1 x bluelgrey T 1 x grey R 1 x black R 1 x clear R 1 x grey T 1 x light blue T 1 x grey T 1 x clear T 1 x bluelgrey T 1 x grey T 1 x light brown T 1 x clear T 1 x grey T 1 x clear T 1 x grey T 2 x grey R 1 x clear R 1 x bluelgrey T 2 x grey R 1 x bluelgrey R 1 x clear R 2 x grey R 1 x grey R 1 x black R 1 x clear R

The transfer and persistence of automotive carpetfibres on shoe soles

from the older cars. The 1987 Mitsubishi Magna transferred the least fibres, followed by the 1989 Toyota Supra. The 1997 Toyota Rav4 and 1997 Ford Fairlane both transferred the most fibres, the Toyota transferring slightly more than the Ford. The 1991 Honda CRX was in the middle for Shoes 1 and 2. However, with Shoes 3 and 4, the Honda CRX actually transferred more fibres than any other car. In Figures 5 to 8, data showing the number of fibres transferred from each of the five car carpets to the four types of soles is presented. Fibres were transferred to the shoe soles by normal activity, although generally not in very large numbers. The greatest number (average 32.8) of fibres were transferred from Car 5 (Honda CRX) to Shoe 3 (rough profile). The least number of fibres (average 0.6) were transferred from Car 3 (Mitsubishi Magna) to Shoe 1 (low profile). It is of interest to note that in no experiment were obvious extraneous fibres seen (i.e. fibres distinguishable from the carpet fibres). The results of the analysis of variance (see Appendix) showed that the carpet, shoe and time period were all significant in determining the number of fibres transferred. The time factor has an influence probably because the number of movements of the shoe soles over the carpet will increase rather than because the shoe soles are in contact with the carpet for a longer period of time, i.e. fibres being rubbed off the carpet. While performing these experiments the experimenter did not have the sides of the shoes in contact with the carpets. However, it was observed that fibres were often found on regions of the sole that had not come into contact with the carpet, for example, on the joint between the inside of the heel and the sole. This suggests that these fibres were not only transferred by a mechanical interaction with the carpet but by some other means. The most likely explanation is that as the shoe soles were moved over the carpet, electrostatic forces were generated, resulting in fibres being

TABLE 5 Persistence of transferred fibres on soles of shoe 4 after five minutes of walking (transferred with normal scuffing; 15 minutes). Shoe sole

Surface group

Total Total transferred remaining

New

Vinyllcarpet

27

Concretelgrass Asphalt

transferred to these places. Therefore the results of this study suggest that electrostatic charges may contribute to fibre transfer involving carpet and shoe soles. Effect of Additional Parameters on the Fibre Transfer The average number of fibres transferred from the carpets when the car mats were present was significantly less (5.0 in total) than the number transferred when they were absent (29.3 in total). This is most likely because contact is with the mat, not the carpet. The construction of the car mat carpet differed from that of the car carpet. It should be noted that the presence of a car mat does not preclude the possibility of finding carpet fibres since the mats generally do not cover the entire floor area and some regions of the car's carpet are still exposed. Depending on where the shoe soles are in contact it would still be possible to transfer fibres from the car carpet when the car mats were in place. A secondary transfer from the mats is also possible. The number of fibres transferred as a result of violent braking was very small compared to the number transferred by normal activity. The average total number of fibres transferred without the car mat was 5.0 compared to 0.8 when the car mat was present. Fibres were easily removed by brushing the sole or by gently blowing over the surface. No fibres were seen to have fused to the shoe sole. The hardest shoe used in the transfer experiments was Shoe 1 (low profile), which also had the least number of fibres transferred. Often the greatest numbers of fibres were transferred to Shoe 3 (rough profile, hardness 62.4-63.0) or Shoe 4 (case profile, hardness 68.1-66.9). The softest shoe sole used was Shoe 2 (medium profile). However, this shoe did not always collect the most number of fibres on average. Therefore, hardness does not appear to be a significant factor influencing the transfer of fibres to shoe soles. In addition, the hardness of the shoe sole did not significantly decrease after exposure to outdoor conditions for 24 hours. The authors' results indicate that this parameter is not of great relevance to the transfer of automotive carpet fibres to shoe soles.

TABLE 6 Persistence of transferred fibres on soles of shoe 4 after five minutes of walking (transferred with vigorous scuffing; 30 minutes).

Percent remaining

Shoe sole

Surface group

6

22%

New

Vinyllcarpet

60

11

18%

15

0

0%

Concretelgrass

72

0

0%

31

2

6%

Asphalt

122

19

16%

DamagedVinylIcarpet

19

0

0%

DamagedVinylIcarpet

75

1

1%

Concretelgrass

39

0

0%

Concretelgrass

73

0

0%

46

4

9%

Asphalt -

246

30 -

0 -

0% -

--

Asphalt -

Total Total transferred remaining

-

Percent remaining

Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAIGHT and J ROBERTSON

Persistence of automotive carpet fibres transferred on shoe soles The persistence of fibres transferred after normal transfer is summarised in Table 5 and the persistence of fibres transferred after vigorous transfer is summarised in Table 6. The data presented demonstrate that the number of fibres transferred depended on the following factors. The level of activity with larger number of fibres being transferred with more vigorous "scuffing" action. The level of wear of the recipient shoe sole with more fibres being transferred onto new unworn soles than onto the artificially scuffed and worn sole surface. Overall it can be seen that very few fibres (between 0-6 fibres in most cases) persisted even over the short time frame of five minutes. No fibres persisted when the experimenter walked on concrete and grass. In two instances more

than 10 fibres were remaining (percentage of persistence between 16% and 18%).These two trials involved vigorous transfer activity followed by walking on vinyllcarpet or asphalt. The level of activity during the transfer did not appear to have a significant effect on persistence. In all cases the fibres that did persist after walking for five minutes over the different surfaces were seen to be either physically caught in the rubber at the edge of the sole or were in a recessed area of the sole that did not directly come into contact with the ground. No fibres remained on the heel section of either pair of soles after either transfer method. This is highly relevant for the case under investigation because fibres were recovered from the heels of the victim's shoes. The purpose of the second persistence experiment was to determine if any fibres would remain on the shoe soles after

TABLE 7 Transfer and persistence results for the same shoe soles (4) worn by different experimenters and using different car car~ets. Carpet A

Trial and shoe

Carpet B

Carpet C

Carpet D

Fibres Fibres Percent Fibres Fibres Percent Fibres Fibres Percent Fibres Fibres Percent transferred remaining remaining transferred remaining remaining transferred remaining remaining transferred remaining remaining after 5 min after 5 min after 5 min after 5 min after 5 min after 5 min after 5 min after 5 min

1 Right

55

3

5.5%

19

0

0.0%

224

2

0.9%

101

0

0 .O%

1 Left

76

3

3.9%

3

0

0.0%

49

1

2.0%

141

2

1.4%

2 Right

60

15

25.0%

8

0

0.0%

23

0

0.0%

35

0

0 .O%

2Left

75

0

0 .O%

8

0

0.0%

75

0

0.0%

50

0

0.0%

3 Right

72

3

4.2%

3

0

0.0%

49

1

2.0%

127

2

1.6%

3 Left

45

3

6.7%

19

0

0.0%

224

2

0.9%

101

0

0.0%

4 Right

54

1

1.9%

14

1

7.1%

44

0

0.0%

5

0

0.0%

5 Right

39

0

0 .O%

6

0

0 .O%

87

0

0.0%

51

1

2.0%

5 Left

56

2

3.6%

12

2

16.7%

13

0

0 .O%

62

1

1.6%

6 Right

71

0

0.0%

2

0

0.0%

13

0

0.0%

59

0

0 .O%

6 Left

69

1

1.4%

3

0

0.0%

40

1

2.5%

8

0

0.0%

7 Right

28

3

10.7%

1

0

0.0%

28

1

3.6%

57

18

31.6%

7 Left

135

6

4.4%

7

0

0 .O%

14

0

0 .O%

46

8

17.4%

8 Right

95

13

13.7%

69

20

29.0%

70

16

22.9%

98

11

11.2%

8Left

36

7

19.4%

64

16

25 .O%

80

8

10.0%

300

15

5.0%

9 Right

55

3

5.5%

19

2

10.5%

244

2

0.8%

101

0

0.0%

9 Left

76

3

3.9%

3

1

33.3%

49

1

2.0%

141

2

1.4%

Mean

61.9

3.8

6.8%

14.7

2.4

7.9%

75.7

1.9

2.6%

82.9

3.3

4.1%

S.D.

26.7

4.2

6.9%

19.8

5.8

11.6%

74.8

4.0

5.6%

69.2

5.7

8.3%

Science & Justice 1999; 39(4): 239-251

247

The transfer and persistence of autonaotive carpetfibres on shoe soles

they had been worn while walking in realistic conditions over various surfaces (vinyl, carpet, concrete, grass and asphalt) for 30 minutes. No fibres remained at all after 30 minutes even after a vigorous transfer regime specifically aimed at ensuring the transfer of a large number of fibres. Additional transfer and persistence experiments Effect of the wearer The transfer and persistence of fibres are presented in Table 7 and the results show that the wearer has an influence on both the transfer and the persistence. They also confirm the influence of the nature of the carpet. However, although interpersonal differences exist, the authors' data confirm the poor persistence of fibres transferred on shoe soles. In 30 out of 72 cases (41.7% of cases) no fibres remained on the soles after a five minutes walk on smooth surfaces. In 53 trials (73.6% of cases) at least 95% of the transferred fibres were lost after this short walk. The number of persistent fibres is generally very small. The average number of fibres found per sole after five minutes varies from 1.9 to 3.8 depending on the carpet. More than five fibres were found in only 12 cases (16.7% of cases). The maximum number of fibres found on one sole was 20.

Effect of marks and impressions These results (Table 8) are very similar to those obtained in the previous experiment: interpersonal differences exist, but the persistence of the transferred fibre is very poor. Rubbing the case soles on a ribbed surface did not increase the persistence and no fibre appeared to be fused in the sole material. Effect of a sticky substance on the soles The results (Table 9) show that the presence of sticky substance on the soles increases both the transference and persistence of carpet fibres to the soles. When a sticky substance is present, the number of transferred fibres is increased by a factor of 3, and the number of persistent fibres is increased by a factor of 14 in comparison to a 'clean' sole. On average approximately half of the fibres remained after a five minutes walk, compared to less than seven percent for the same carpet when the soles are clean. However, this increase in persistence could be wholly attributed to fibres retained on the areas visibly covered with sticky substance. Occurrence of automotive carpet fibres Of the 53 surveys completed, 46 were drivers and seven were passengers. Eighteen of the 46 drivers (39%) and six of the seven passengers (86%) reported finding fibres. The majority of shoe soles had less than five fibres, and the greatest number of fibres found on one shoe sole was 14 (Figure 9).

The authors' results indicate that there is a greater likelihood of finding car carpet fibres on passengers' shoe soles than on drivers' shoes. As either one or both shoes of a dri-

ver spend a considerable amount of time on the pedals of the car and not on the carpet, this result is not surprising. There may also be differences between manual and automatic cars. It is possible that drivers of manual cars have less chance of finding fibres on their shoes than automatic drivers, especially on the left shoe. The length of the journey did not appear to influence the likelihood of finding fibres on shoes. The longest a person (driver) had been in a car was 70 minutes and no fibres were found on their shoe soles. The year of manufacture did not influence whether or not fibres were found. In contrast, Scott [8] and the results of the previous transfer experiments showed that newer car carpets shed more fibres than older ones. This discrepancy can be explained by the fact that the age of the carpet is only one component of the equation. The carpet type, its sheddability and how well it wears, along with the type of shoe soles involved in the transfer, are probably more significant factors than the age only. In this regard, it was noted that, in most cars (75%), the carpet had a low or medium sheddability (1 to 3 in the arbitrary scale from 1 to 5). The presence of car mats did not affect whether fibres were found or not. The question did not specify what type of car mat was in the car and there are various types, e.g. rubber, carpet or a combination of both. Drivers' side carpets in newer cars also have a rubber mat built into the carpet. In the cases where fibres were found, the car mats themselves may have been made of carpet and these could have been the source of the fibres. This was not clear from the questionnaire. The results of the questionnaire do suggest that the profile of the shoe is an important influence on whether fibres are transferred or not. Three of the four high profile shoes reported in the survey were found with fibres. The other types of profiles only had fibres on 4 0 4 7 % of the total number of shoes.

!

5

,

7

8

9

10

11

12

I >

Id

15

number of fibres

FIGURE 9 Occurrence of finding carpet fibres on shoe soles of people at the end of a car journey. passenger W driver

Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAlGHT and J ROBERTSON

TABLE 8 Transfer and persistence results for the same shoe soles (4) worn by different experimenters after rubbing on a striated rubber stool pad (carpet A). Trial and shoe

Fibres Fibres remaining transferred after 5 min

% remaining

a f e r 5 min

Trial and shoe

1 Right

5 Right

1 Left

5 Left

2 Right

6 Right

2 Left

6 Left

3 Right

7 Right

3 Left

7 Left

4 Right

Mean

4 Left

S.D.

Fibres Fibres remaining % remaining transferred after 5 min a f e r 5 min

TABLE 9 Transfer and persistence results for the same shoe soles (4) worn by different experimenters after stepping in Coca Cola (carpet A). -

Trial and shoe

Fibres Fibres remaining transferred after 5 min

% remaining

a f e r 5 min

Trial and shoe

1 Right

6 Right

1 Left

6 Left

2 Right

7 Right

2 Left

7 Left

3 Right

8 Right

3 Left

8 Left

4 Right

9 Right

4 Left

9 Left

5 Right

Mean

5 Left

S.D.

The likelihood of finding fibres on the shoe soles also seemed to diminish if the soles were damaged or marked a somewhat surprising result. The questions may have been interpreted differently by different respondents. These results require further investigation. It should be pointed out that forensic science students took part in this experiment in order to get significant data in a reasonable time. Their level of training was sufficient and appropriate with regard to the kind of examination carried out and the purpose of the experiment (the differentiation carpet vs. mat was generally straightforward). Only visual comparisons of the fibres were carried out. The respondents may have counted all the fibres as having come from the car carpet unless they were obviously distinct. Science & Justice 1999; 39(4): 239-251

Fibres Fibres remaining % remaining transferred after 5 min after 5 min

Therefore these results may overestimate the likelihood of finding car fibres on shoes. Overall, the results indicate that there is a relatively good chance of finding carpet fibres on the shoe soles of poeple about to leave their car. However, the likelihood of finding a large number of fibres (>5) on such soles is rare. Frequency of the combination of fibres The majority of the car carpets sampled were grey in colour, and this was largely independent of the car's outer colour. However, there was a wide variation in the colours and cross-sectional shapes (principally round and trilobal) within these grey carpets, even among a given car make. Of the carpet samples examined, 53.1% contained only one fibre type, 32.0% and 12.0% contained respectively two 249

The transfer and persistence of autc9rnotive carpet fibres on shoe soles

and three fibre types, and only 2.8% had four or more different fibre types, the greatest number of types being five. It is possible, given the marked differences in fibres of Hondas of 1990, 1991 and 1992, that the type of carpet found in the defendant's car was used only for a relatively short period, or in specific models. This hypothesis is supported by some information received from Honda, Japan (personal communication). After stereomicroscopic examination the only carpet with a combination of fibres which looked as if it might have been similar to that of the evidential sample was from a Honda Civic of the same year of manufacture as the defendant's car. However, further examination of this sample showed that each of the three types was composed of polypropylene, whereas the evidential sample and the carpet of the defendant's car were composed of polyester and polypropylene. None of the vehicles surveyed (including 29 Hondas) was found to contain front floor carpet composed of a similar combination of fibres to the evidential grey polypropylene, blue polypropylene and black polyester fibres. This suggests that it is rare to find a carpet made of such combination of fibres, even in the Honda population.

Conclusions The present study prompted by a particular case has extended previous research by investigating the transfer of car carpet fibres to shoe soles under conditions as close to real life as possible. The data obtained bring valuable information for the interpretation of fibre evidence. Results from both the questionnaire and the transfer and persistence experiments showed that fibres could be transferred from car carpets to shoe soles by normal activity in real life conditions. The transfer experiment results indicate that newer car carpets shed more fibres. However, these fibres do not persist for very long after walking. Most are lost after five minutes and all are lost after 30 minutes. Walking over grass eliminates all fibres in a short period of time. Many factors were found to be important in determining the extent of fibre transfer. The particular carpet and particular shoe sole used in the transfer were the most important. A longer contact time usually resulted in greater fibre transfer, most likely because of an increase in the number of contact passes. Fibres were transferred when car mats were present, although in a reduced number. Arguments that large numbers of fibre could be transferred from violent braking, or because of variations in hardness of the shoe sole caused by environmental conditions, were not supported by the results of the present study. The authors' results do not support the hypothesis that fibres could persist because of a fusing process resulting from the rubbing of the soles on a ribbed

surface. It appears that finding any fibres on the shoes of an individual would indicate very recent contact unless there were obvious reasons why fibres had not been lost, such as the presence of sticky residue. The survey results indicate that there is a relatively good chance of finding carpet fibres on the shoe soles of poeple about to leave their car, although the number of individual fibres is generally low. There is also a high degree of variation of fibres in the automotive carpets population, which improves the value of the discovery of "matching" automotive carpet fibres. Overall, this study has confirmed that fibres can be good evidence of contact in circumstances involving car carpets and shoe soles. It has also emphasised the fact that it is of prime importance to collect victim's and suspect's exhibits as soon as possible after the event. A detailed case study will be presented in a future work, along with the hypotheses proposed by the parties and how these hypotheses are supported or denied by our experimental results.

Acknowledgement The authors would like to thank the Forensic Services Group of the New South Wales Police Service for their collaboration and for allowing them to use actual case materials for their experiments. References 1. Locard E. L'enquCte criminelle et les mkthodes scientifiques. Paris: Flarnmarion, 1920: 139. 2. Pounds CA and Smalldon KW. The Transfer of Fibres between Clothing Materials during Simulated Contacts and their Persistence during Wear - Part 1 : Fibre Transference. Journal of the Forensic Science Society 1975; 15: 17-27. 3. Pounds CA and Smalldon KW. The Transfer of Fibres between Clothing Materials during Simulated Contacts and their Persistence during Wear - Part 2. Fibre Persistence. Journal of the Forensic Science Society 1975; 15: 29-37. 4. Pounds CA and Smalldon KW. The Transfer of Fibres between Clothing Materials during Simulated Contacts and their Persistence during Wear - Part 3: A Preliminary Investigation of the Mechanisms Involved. Journal of the Forensic Science Society 1975; 15: 197-207. 5. Kidd CBM and Robertson J. The Transfer of Textile Fibres during Simulated Contact. Journal of the Forensic Science Society 1982; 22: 301-308. 6. Robertson J, Kidd CBM and Parkinson, HMP. The Persistence of Textile Fibres Transferred during Simulated Contacts. Journal of the Forensic Science Society 1982; 22: 353-360. 7. Robertson J and de Gamboa, XM. The Transfer of Carpet Fibres to Footwear. Proceedings of the 10th International Association of Forensic Sciences, Oxford, 1984. 8. Scott H. The Persistence of Fibres Transferred during Contact of Automobile Carpets and Clothing Fabrics. Journal of the Canadian Society of Forensic Science 1985; 18: 185-199. 9. Grieve MC, Dunlop J and Haddock, PS. Transfer Experiments with Acrylic Fibres. Forensic Science International 1989; 40: 267-277.

Science & Justice 1999; 39(4): 239-251

C ROUX, S LANGDON, D WAIGHT and J ROBERTSON

Appendix Analysis of variance for the effects of car carpet, shoe sole and time period Source of variation

Degrees of freedom

Carpet Sole Time Carpet x sole Carpet x time Sole x time Carpet x sole x time Within + residual

Science & Justice 1999; 39(4): 239-251

Sum of squares

Mean square

F

Signijkance level