Factors affecting the potential for fibre contamination in purpose-designed forensic search rooms

Transcription

1 SCENTFC & TECHNCAL Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms C ROUX*, J HUTUNEN, K RAMPLNG Department f Chemistry, Materials and Frensic Science, University f Technlgy, Sydney, PO Bx 123, Bradway NSW 2007, Australia and JROBERTSON Frensic Services, Australian Federal Plice, GPO Bx 401, Canberra ACT 2601, Australia This study investigated fibre mvement within and ut f a search rm, when perfrming a garment examinatin. The effect f the cllectin prcedure (taping v. scraping) n the number f cntaminant fibres prduced, and the effectiveness f a number f cleaning techniques and varying degrees f examiner hygiene were als studied. Fibre mvement was fund t be dependent upn distance, with fibre ppulatins decreasing with increasing distance frm the garment examinatin area. Mst fibres were depsited during the actual examinatin. Cttn fibres were mre easily shed and als fund t be airbme fr lnger perids f time than wl, acrylic and plyester fibres. The 'scraping methd' f fibre recvery was fund t result in an increase in the number f lse fibres with transfer t the examiner's clthing and a number f fibres exiting the search rm. t is unlikely that a cmpletely clean search rm can be btained. Hwever, with prper precautins it is pssible t minimise and mnitr the cntaminant fibre ppulatin. These features are presented and discussed in this paper. Cette etude evalue le muvement de fibres a l'interieur et hrs d'un labratire de recherches de traces lrsqu'un vetement est examine. L'effet du prcessus de cllectin (adhesif cntre peignage) sur le nmbre de fibres de cntaminatin prduites et l' efficacite de diverses techniques de nettyage et les differents degres d'hygiene de l' examinateur nt egalement ete etudies, Le muvement de fibres est dependant de la distance avec les ppulatins de fibres qui decrissent lrsque la zne d'examen de 'habit est a une distance plus elignee. La plupart des fibres nt ete depsees pendant 'examen luimeme, Les fibres de ctn nt ete perdues plus facilement et egalement retruvees dans l' air pur des perides de temps beaucup plus lngues que la laine et les fibres acryliques et plyesters. La methde par peignage pur reclter des fibres prduit une augmentatin du nmbre de fibres libres avec transfert sur 'habit de 'examinateur et un certain nmbre de fibres srtant de la zne de recherche. l est imprbable qu'une salle de recherches cmpletement prpre puisse etre btenue. Cependant avec des precautins adequates, il est pssible de minimiser et de determiner la ppulatin de fibres cntaminantes, Ces elements snt presentes et discutes dans cet article. Science & Justice 2001; 41: Received 26 February 2001; accepted 24 April 2001 The Frensic Science Sciety 2001 * Crrespnding authr, Fax: , claude.rux@uts.edu.au Es wurde wahrend der Spurensicherung an einem Bekleidungsstuck die Faserverschleppung innerhalb eines Spurensicherungsraums und aus diesem heraus untersucht. Die Auswirkung der Spurensicherungsmethde (Klebeband versus Scraping) auf die Anzahl der entstehenden flttanten Fasem, die Effektivitar einer Reihe vn Siiuberungstechniken swie unterschiedliche Hygienegrade des Spurensicherers wurden ebenfalls untersucht. Mit zunehmender Entfemung vm art der Sicherung verringerte sich die Anzahl der flttanten Fasem. Die grfste Anzahl slcher Fasem erzeugte der Sicherungsvrgang. Baumwllfasem wurden besser abgegeben und hielten sich langer in der Luft als Wll-, Acrylund Plyesterfasem. Durch die Scraping-Methde entstanden mehr flttante Fasem, die sich nicht nur auf die Bekleidung des Sichemden iibertrugen sndem sich auch im Raum ausbreiteten. Es ist unwahrscheinlich einen vllstiindig reinen Spurensicherungsraum zu schaffen. Mit geeigneten Vrkehrungen ist es jedch mglich, die Anzahl flttanter Fasem zu minimieren und die kntaminierende Faserppulatin aufzuzeichnen. Este estudi investig el mvimient de las fibras dentr y fuera de la habitacin de biisqueda cuand se realiza una investigacin de rpas. Se estudi tambien el efect del prcedimient utilizad (glpe versus rascad) sbre el mimer de fibras prducidas, la eficacia de una serie de tecnicas de limpieza y diverss grads de higiene del examinadr. Se encntr que el mvirnient de las fibras era dependiente de la distancia, decreciend la pblacin de fibras al aumentar la distancia al area de examen de la rpa. Muchas de las fibras se depsitaban durante el examen en curs. Las fibras de algdn se pelaban cn mas facilidad y se mantenfan.en el aire durante mas tiemp que las de lana, acnlicas 0 de pliester, Se encntr que el metd de rascad para la btencin de las fibras prducfa un aument en el mimer de fibras sueltas que se transferfan a la rpa del examinadr y que salfan de la habitacin de busqueda, Es imprbable que se pueda tener una habitaein de busqueda ttalmente limpia. Sin embarg, cn ciertas precaucines, es psible minimizar y mnitrizar la pblaci6n de fibras cntaminantes. Ests rasgs se presentan y discuten en este trabaj. Key Wrds: Frensic science, criminalistics, fibres, cntaminatin, recvery, prtcls, taping, scraping, search rms. 135

2 Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms ntrductin Fibres prvide valuable evidence in a variety f categries f investigatin and can still assume vital imprtance in sme instances [1]. Their use, analysis and value have been widely investigated and dcumented fr the last twenty years [2-6]. n the labratry, the first step f frensic fibre examinatin invlves searching and cllecting extraneus fibres n the surface f exhibits, ften garments. Best frensic practice invlves the use f search rms, which are set aside specifically fr this purpse. This is t minimise the ptential fr cntaminatin frm surces that exist in the generallabratry envirnment due t the nature f garments and their ability t shed fibres easily. n general, cntaminatin can fall int tw categries. The first type f cntaminatin is that cnfmed t a particular case, where fibres frm ne evidential item are transferred t anther item fllwing cllectin by a plice fficer r a crime scene examiner. t may be caused by a primary transfer (e.g. tw garments are packaged r transprted tgether), r by a secndary r higher degree transfer. Secndary cntaminatin may result frm tw garments being examined in the same search rm, withut prper cleaning between examinatins, r by the examiners passing fibres frm ne garment t the ther via their clthing r hands. The secnd type f cntaminatin is knwn as envirnmental cntaminatin and is caused by garments being placed in the same envirnment where they bth cllect fibres riginating frm that envirnment. Fr example, tw garments expsed t the same envirnment within a labratry may result in the transfer f backgrund fibres t each f the items. The implicatins f fibre cntaminatin during frensic casewrk are very serius as it may result in what is knwn as a false psitive, leading t a wrngful accusatin, arrest and subsequent cnvictin. A recent example f such a miscarriage is that f the cnvictin, and later exneratin, f Guy Paul Mrin in Canada, in Mrin was cnvicted fr the murder f Christine Jessp with fibre evidence being a majr part f the prsecutin's case. An inquiry int the case was held in 1996, fllwing Mrin's acquittal in 1995, and fund a number f crucial errrs, including cntaminatin f the evidence whilst at the labratry. The items were believed t have been cntaminated by a persn handling the evidence whilst wearing a red sweater withut a labratry cat r ther prtective clthing. The fmdings f the inquiry, by Kaufman [7], called fr mre stringent prcedures t reduce the pssibility f cntaminatin, as well as research int the develpment f mre universal best practices regarding fibre examinatins. Despite the paramunt imprtance f the cntaminatin issue, nly ne study has been published int the pssibility f cntaminatin ccurring during fibre searches within the labratry. Mre and c-wrkers [8] fund that significant airbrne material was nt nly prduced, but als capable f mving small distances (abut 1.2 m) between benches. Small amunts culd even be fund several days after the cmpletin f the examinatin itself. Hwever, their mst signifcant finding was that fibres were nt transferred between adjacent rms. This wuld make the use f separate rms fr "knwn" and "unknwn" samples wrthwhile in preventing cntaminatin. The paucity f research in this area prmpted the present study that investigated fibre mvement, bth within and ut f frensic search rms. The effect f the cllectin prcedure n the number f cntaminant fibres prduced, and the effectiveness f a number f cleaning techniques and varying degrees f examiner hygiene, were als studied. Materials and Methds This study invlved experiments whereby lse fibres were generated and transferred int the envirnment via mck garment examinatins. These fibres were systematically sampled and cunted, and the results were analysed with respect t the fllwing parameters: distance; time; fibre type; cllectin and cleaning; and prtective prcedures. Garments Fur garments were used in these experiments (Table 1). Garment A was used fr tw separate series f experiments cnducted tw years apart in rder t test the repeatability f the trends bserved. TABLE 1 The fur garments used in this study. Garment Fibre Type Clur Brand Appearance Garment Shed A Cttn Orange Espirit Ribbed knit lng-sleeved sweater High B Acrylic Purple St James Shrt-sleeved knit sweater Medium C Wl Marn St James Sleeveless knitted vest High D Plyester Red Miss Shp Smth and shiny knee-length skirt Lw NB: Garment sheddability was assessed by cunting the number f fibres cllected by a 7.5 cm length f tape after nly ne pressing, using Cxn et al. [9] fr guidance. 136

3 C ROUX, J HUTTUNEN, K RAMPLNG and J ROBERTSON Search rm preparatin A ttal f fur search rms were used; tw frm ne frensic labratry and tw frm anther. n all but experiment 4, the rms were cleaned using a nn-shedding clth and 70% ethanl in water t wipe the main examinatin table and side benches and then mpping the flr using water and a spnge mp. During the cleaning the examiner wre a 100% plyprpylene prtective suit. A piece f brwn paper was placed and taped t the examinatin table t cver the wrking area (apprximately half f the table). A piece f white butcher's paper was then placed n the tp f the brwn paper and gently wiped with a nn-shedding clth mistened with a 70% ethanl slutin. Mck examinatin Garments were subjected t mck examinatins fllwing tw different standard prcedures: taping and scraping. Fr the taping methd, the garment was laid ut n the wrk-area, frnt upward, and searched with glved hands using tweezers and a magnifying lens fr seven minutes. The garment was then turned ver and searched in the same manner fr a further seven minutes. Fr the fllwing seven minutes, three pieces f adhesive tape were used t tape-lift the back f the garment and a further three pieces were then used t tape-lift the frnt. The garment was then gently shaken ver the wrk-area fr fur minutes. n the scraping technique, after the initial search using tweezers, the garment was hung using a vertical adjustable metal frame and scraped with a metal spatula n the frntside fr tw minutes and then n the back-side fr an additinal tw minutes. During this prcess the tp f the garment was apprximately at 110 em abve the table surface. This technique was applied at the end f the study and nly with garments A and B. Sampling Thrughut this study, cntaminant fibres present at selected lcatins were cllected using bth active and passive sampling. Active sampling invlved the use f 15 em lengths f 2.5 em wide clear adhesive tape. Whilst hlding with bth glved hands, the tape was placed nt the area t be sampled and pressed dwn with a finger. t was then lifted and the area was "scanned", the prcedure being repeated fifteen times fr each piece f tape. The tape was then placed nt a piece f A4 transparent acetate backing sheet, which was then labelled with relevant infrmatin. Passive sampling invlved pieces f 15cm x 15cm clear self-adhesive bk cver. These were placed, adhesive side up, in the area t be sampled and held dwn by placing tw micrscpe slides n ppsite edges. Fllwing expsure fr a set perid f time, the adhesive was cllected by placing a piece f A4 acetate ver the cntact and then taping the edges t prevent cntaminatin. The sheets were als labelled with the relevant infrmatin. Side-bench CUpbards m Adhesives 1.4m Gap Lc Om Adhesives O.Sm Adhesives Examinatin Table P OO ~arment FGURE 1 Setup used fr Experiment 1. Eight adhesives were placed ut at three distances at the beginning f the experiment, and then cllected at certain times after cmpletin f the examinatin. Bth types f samples were searched fr the relevant target fibres using a Leica MS5 lw-pwer steremicrscpe (x 16 t x 40) as well as a Maxcan Micr mager autmatic fibre finder. Results btained by the latter were manually checked fr accuracy. Experiment 1: Fibre mvement and distance within the search rm This experiment was designed t find ut hw fibres mve with respect t bth time and distance. The set-up invlved three sets f up t eight upturned pieces f tape: at half-ametre, ne metre and three metres frm where the mck garment examinatin was cnducted (Figure 1). During the examinatin, the adhesives cllected fibres shed frm the garment. Then immediately after the examinatin, ne adhesive frm each f the three sets was cllected. Anther ne was cllected 15 minutes later, and the rest were cllected at set times ver the next 48 hurs. N activity ccurred in the rm during this perid. Pieces f tape were als lcated at several lcatins (e.g. drway, stre rm) arund the rm fr the duratin f an examinatin in rder t investigate the mvement f fibres ver shrt distances. Experiment 2: Fibre mvement and time within the search rm Experiment 1 was mdified slightly in rder t give a clearer picture f what was happening with respect t time. Only ne adhesive was lcated at each f the three distances 137

4 Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms Cupbards 3.0m Adhesive Tutrial:'entre sample Site) Side-bench 1.4m Gap Frensic WetChemis Labratry Seq>1-eSite2 Apprximate Dimensin alng the Crridr frgeneralenvirnrner SamplingSites andtheir RelativeLcatins plyprpylene prtective suits and rdinary labratry cats (cttn:plyester, 50:50) befre and after the examinatin. FTR Rm $a.. lesi::efficefyer s"";lesite4 Examinati= ~, Table rment FGURE 2 Setup used fr Experiment 2. Only ne adhesive was placed at each f the three distances at the beginning f the experiment, and they were replaced at set times. during the examinatin (Figure 2). At the end f the examinatin, these three pieces f adhesive were remved and replaced with anther set. This was repeated at set times ver the fllwing tw days during which there was n ther activity in the Search Rm. Experiment 3: Fibre mvement ut f the search rm As there were a number f examinatins cnducted using Garment A in ne f the tw frensic labratries, several adhesives were placed n the flr in different rms and crridrs adjacent t the search rm, at a distance f 3 m t 53 m frm the actual examinatin bench (Figure 3). Garment A was nt expsed in any f these rms and crridrs at any time. Hwever, the activity in these rms was nrmal and n precautins were taken t stp cntaminatin by the target fibres. The cllectins were stpped after fur weeks. Experiment 4: Hygiene in the search rm This experiment sught t examine hygiene and cleaning practices in the search rm. T bserve the effectiveness f cmmn precautinary steps, simulatins were perfrmed exhibiting different degrees f precautin against cntaminatin by material leftver frm previus examinatins. Mck examinatins were perfrmed n separate days, with at least ne day in between each experiment with Garment A. Cleaning prcedures invlved mpping r sweeping the flr, and wiping the examinatin table with a dry paper clth, a paper clth mistened with a 70% ethanl slutin, a dry nn-shedding clth and a nn-shedding clth mistened with a 70% ethanl slutin. The effectiveness f the prtective garment was als tested by tape-lifting single-use Analytica.D'lemistry Labratry ~lesitel FGURE 3 The relative lcatins f the ther rms that were sampled (Experiment 3) Results n rder t limit the amunt f data, and fr cnsistency purpses, the results presented belw are thse btained using the search rms lcated at the University f Technlgy, Sydney. The data acquired at the Australian Federal Plice, Canberra, led t similar bservatins. Experiment 1: Fibre mvement and distance within the search rm All garments examined shwed a similar trend cncerning fibre mvement with distance: mre fibres were depsited at shrter distances (Figures 4-9). The actual number f fibres prduced was variable and depended upn the sheddability f the garment. There was n increasing trend fr the fibre cunt with time, i.e, mst fibres were depsited at r shrtly after garment examinatin. The apparent sinusidal pattern was identified as an artefact due t the air ventilatin system, and culd be cnsidered as nise. These general trends were nt affected by the cllectin methd (taping v. scraping) applied. Hwever, the scraping methd prduced between tw and six times mre target fibres than taping. Als, scraping generated increased numbers f target fibres at all three distances. Small numbers f fibres were fund n adhesives left in the space under the dr between the drway and the search rm after the examinatin f any garment using the taping methd (0 t 6 fibres maximum). n cntrast, 25 t 63 fibres were fund n adhesives lcated at the same lcatins with the scraping methd applied t Garment A. The scraping f 138

5 C ROUX, J HTJ7VNEN, K RAMPUNG and J ROBERTSON 160 ua g 12a ~ 1aa :S sa.4-,j ~ s ~ 4a..,.. Ti~ frm Examinat:ic:m [Ht FGURE 4 Number f fibres foobdn a 15 em x 15 COlarea after the examinatin f Garment A (taping). Experiment m: -.- 1m: m: g 40 u 35 ~ 30.Q i>: ~ 15 H tl a - - ~--- ~- - -!:_- ~ - - -~ - - ~--~ a a.25.s Time fi6m Examinatin 1 FGURE 7 NUlberf fibres fund n a 15 COl x 15 em area after the examillatinf Garment B(scntping). Experiment 1 0,5 m:-+- 1m:_3 m: a.w3S0 <3 30a ~ 25a.0. rl ~.1-50 "'2aa ~ 100 s a ~_""' ~ _~_~4 4! FGURE 5 Nwnber f fibres fund n a 15 em 15 em area after the examillatin f Garment A (scraping). Experiment 1 O.5m: lb.: _ 3m: J-, 0 u Q) k.q... 11< '-' 0), e' n1 24 E< ~~---"~~ * A ' Time frm Examinatin FGURE 8 NUlBberQffibres fund n. 15em x 15COl area after the examillatin f Garment C (taping). Experiment :-.- m:_ 301: " g u Q) k.q rl > "Q) Ol 10 M < ~--~---_._--~---~-~ Time frm Examinatin '-' a :> 14-0 t. 12 e.q 10 ~ri 8.,l.J "" Q) Ol 6 M 4 < ~. * * Time frm Examina FGURE 6 NUlBberf fibres fund n a 15 COl S em area after the exllmifiatinf Garment B (taping). Experiment m: m: _ 3 m: FGURE 9 NUlBberf ibn!s fund n a 15 em 15 COl area after the exllmifiatinf Garment D (taping). Experiment 1 0.5b.:-.- 1m: _ 3ll:-. - Garment B, hwever, was nt fund t increase the number f targets being present under the drway in cmparisn t taping. Experiment 2: Fibre mvemen: and time within the search rm DUring the examinatin fibres were depsited at all three distances, in a fashin similar t what was bserved in Experiment. 1, with mre fibres at shrter distances (Figures ). After the examinatin there were very few fibres, if any, depsited at all three lcatins when using the taping Science &: JUstice 2l()1; 41(3): methd. Hwever, target fibres frm Garment A were bserved t still be present within the rm up t 24 hurs a.ft rthe garment bad been scraped. n general, thenumbers f fibres fund during the examinatin were significantly larger (mre than threefld) when scraping was used rather than taping. Garment B, with a lwer shed ptential, prduced nly a slightly increased number f fibres with scraping cmpared t taping. Experiment 3: P'ibre mvement (Jut f the search rm Nne f the adhesives left expsed fr fur weeks ut f the 139

6 Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms ẉ : 1000 "0 ".. 100,q 'rl 10 w.. "OJ E-< 1 0 ~ ;" {> ~ ~ ~ ~ ; <;>"J... 'v 1><'.r J" ~ «<;{ <;{"i ~. ~.... 'V 1><' ~ Time interval (hurs) ẉ : 100 "0 "..,.Q 10 'rl.. W OJ ".. E-< ~ ~ ; "" {> ~ ~ ~ ~ <;>"J... ~. 1><'.r.~ J" ~1 <{ <;{ <;{"i ~.... 'Y' 1><' ~ Time interval (hurs) FGURE 10 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment A (taping). Experiment 2. Lgarithmic scale. 0.5m:. 1m:. 3m:D FGURE 13 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment B (scraping). Experiment 2. Lgarithmic scale. 0.5 m:. 1 m:. 3 m: D w 1000 i'::~~~ ;,~ {> "' <:3 ~ ~ <:3 ; ~.... ~'.t. 1><' <;{.~ J" «<;{"i ~"y ~.... 'v 1><' - Time interval (hurs) w " 100 "0 u " H 10 ::l w 1 " OJ.. E-< ~ ~ ~ ;,~ {> ~ '<::> '<::> ~ ; <;>"J... ~. 1><' <{ <;{.r <;{"i.~ J" ~. ~ ~.... 'Y' 1><' - Time interval (hurs) - FGURE 11 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment A (scraping) Experiment 2. Lgarithmic scale. 0.5 m:. 1 m:. 3 m: D FGURE 14 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment C (taping). Experiment 2. Lgarithmic scale. 0.5m:. 1m:. 3m:D 100 w u " U"0 OJ OJ 10.a H 10 H rl S e,. w OJ " OJ 1 H H E-< E-< ~ ~.~... ~' 1><' ~ J'-Y <{ <;{ <;{"i ~ ~ <;>"J ~ ~ i~ ~ ~. ~.... 'Y' 1><' ~ Time interval (hurs) FGURE 12 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment B (taping). Experiment 2. Lgarithmic scale. 0.5 m:. 1 m: 3 m: D ~ ;,~ ;.~ Time interval (hurs) FGURE 15 Number f fibres fund n a 15 em x 15 em area after the examinatin f Garment D (taping). Experiment 2. Lgarithmic scale. 0.5 m:. 1 m:. 3 m: D search rm cllected any target fibres. Hence, n fibre mvement was bserved ut f the search rm within the fur-week perid after the mck examinatin. Experiment 4: Hygiene in the search rm The ftstaim f this experiment was t see if the methd used t clean the search rm culd create a greater ptential fr cntaminatin. The data btained did nt shw an increase in fibres settling ver ne r 24-hur perids after 140 sweeping, when cmpared t mpping the flr r n cleaning at all. Hence whether such cleaning steps include mpping r sweeping, this study fund n majr difference in terms f their ability t create airbrne cntaminatin (Table 2). The secnd aim was t study the impact f the cleaning methd n the actual search table. Frm the fur methds used t clean the examinatin table, nly dry paper twels

7 C ROUX, J HUTTUNEN, K RAMPUNG and J ROBERTSON were fund t be less efficient, and even this difference was nly small (Table 3). The use f paper as a table cvering greatly increased the efficiency with which the bench culd be cleaned, since nce the paper was remved there were generally nly few, if any, fibres remaining. n the third trial, the cllectin f material nt prtective clthing during an examinatin was examined (Figures 16-18). With taping as the examinatin methd, the examiner's frnt trs had n average 2.6 times mre fibres when using standard labratry cats cmpared t dispsable suits. The labratry cats als had the ability t retain n average 23% f the transferred fibres fr at least ne hur after the examinatin [the plyprpylene suits were designed t be dispsed f after an examinatin, and hence they were nt tested fr persistence] (Figure 16). With Garment A, scraping transferred 9.3 times mre target fibres t the examiner's clthing, when cmpared t taping. This difference was less significant when Garment B was used (Figure 17). Carry-ver fibres were defined in this study as thse target fibres fund depsited n tape-lifts frm an experiment invlving the garment frm which the target fibre riginated was nt invlved. Only three carry-ver fibres (tw frm Garment A and ne frm Garment B) were fund at a distance f 0.5m fllwing the taping experiments. Depending n the experiment and the lcatin f the sampling, scraping generated mre than five times the number f carryver fibres when cmpared t taping (Figure 18). TABLE 2 Effect f different flr cleaning methds; target fibres = garment A Cleaning Technique Target Fibres Cllected ver h Sample 1 Target Fibres Cllected Target Fibres Cllected ver 1h ver 24h Sample 2 Sample 1 Target Fibres Cllected ver 24h Sample 2 Best Practice: Mpping Average Practice: Neither Mpping r Sweeping Wrst Practice: Sweeping TABLE 3 Effect f different bench cleaning methds; target fibres = garment A Cleaning Technique Dry paper twel Paper twel and 70% ethanl Target Fibre Cunt Target Fibre Cunt Target Fibre Cunt Befre Wiping After Wiping After Wiping Sample 1 Sample (100%) 5 (19%) 7 (26%) 27 (100%) 1 (4%) 2 (7%) Dry nn-shedding clth 19 (100%) 2 (11%) 1 (5%) Nn-shedding clth and 70% ethanl 24 (100%) 0(0%) 1 (4%) JJ 160 :: ;> Q) J..l.0.r! f%< JJ Q) 60 tl1 J..l 40 E-< 20 0.J L L TriaJ FGURE 16 Number f fibres fund after the examinatin f Garment A n a cttn labcat v. plyprpylene dispsable suit. Labcat t=o. Labcat t=60 min:. Dispsable t=o: 0 ~:~~1 ~ 300i ~ u. 200 JJ ~ 150 J..l ~ t, l===~_~ Taping Examinatin Met Scraping FGURE 17 Number f fibres fund after the examinatin f Garments A and B using the taping v. the scraping methd. Garment A. Garment B: 0 141

8 Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms tended t stay airbrne fr much lnger perids f time than wl fibres. The garments made f either acrylic, wl r plyester prduced fewer lse fibres than the cttn garment. t was als bserved that the mvement f acrylic, wl and plyester fibres fllwing examinatin f these garments was minimal cmpared t that f the cttn fibres frm Garment A. Taping Examinatin Met Scraping FGURE 18 Number f carry-ver fibres frm ne experiment t anther using the taping v, the scraping methd. On the examiner:. 0.5 m: 1.0 m: 3.0 m: D Discussin The limitatin f any fibre transfer experiment lies in the difficulty in prducing exactly the same abslute ppulatins in repeat experiments. This is due t the numerus variables invlved and the difficulty in cntrlling these variables. T minimise this prblem in this study, experiments were repeated in a ttal f fur search rms, ver a tw year perid. Similar rders f magnitude were btained between repeated experiments. The authrs are cnfident that the data presented in this paper allws valid generalisatins and cmparisns t be made. Our results shwed that fibre mvement, and hence ptential cntaminatin, ccurred when a garment was examined. n general, mst fibres were depsited at shrt distances during the actual examinatin. That is, very few fibres were depsited at lnger distances (e.g., 3 m) r after the actual examinatin. Hwever, the small numbers f target fibres fund depsited n adhesives placed under the drway t the search rms shwed that fibres culd still mve relatively lng distances within the rm. n n case were fibres fund in ther rms distant frm the examinatin rm r in the crridr. This demnstrates int the general envirnment, a dilutin effect f fibres and supprts the assumptin that the use f physically separated search rms is a wrthwhile practice in rder t minimise the risk f cntaminatin in fibre casewrk. Hwever, it shuld be stressed that the examinatin rms used were specifically designed fr trace evidence prcessing with apprpriate air pressure differentials and that the search prtcls designed were designed t minimise cntaminatin ptential. The extent f fibre cntaminatin nature f the garment (i.e., its sheddability) is mainly affected by the and by the cllectin methd. Fr example, it was bserved in the experiments in which large numbers f cttn target fibres were prduced that small numbers f fibres were still settling within the rm, at the shrter distances up t 24 hurs after the examinatin. (l m and 0.5 m), This agrees with the findings f Mre et a1. [8] wh reprted that cttn fibres Our results als shwed that, with the garments used in this study, scraping t recver fibre evidence prduced mre lse airbrne fibres than taping. n mst cases, between tw and six times the number f fibres were fund t have settled n crrespnding adhesives. This seems t be a particular prblem fr the cttn garment (Garment A) which gave much higher numbers f airbrne fibres when scraped, as cmpared t taped. The fibres which remain within a search rm after an examinatin are a very serius matter due t the pssibility f thse fibres transferring t ther garments r evidential items during subsequent examinatins. n this respect, the high number f ptential cntaminant fibres generated by scraping is primarily an issue in relatin t cleaning. Fr example, in ur scraping experiments, a number f range cttn fibres (Garment A) were fund t be still present in the rm fllwing cleaning and then further examinatin f anther garment. n ne experiment tw separate cleaning steps using the best practice failed t remve the "residual" range cttn fibres after Garment A was scraped. Hence, the cleaning practices administered in this study were ineffective in remving the large numbers f lse fibres prduced by scraping Garment A. These results demnstrate that the applicatin f effective hygiene practices is a significant issue fr labratries using scraping as a standard recvery methd. Similarly, the larger number f fibres prduced by scraping resulted in a significantly larger number f fibres being transferred t the prtective suit f the examiner, which in tum culd be a ptential surce f cntaminatin between garments. Recvery techniques shuld aim t cause the minimum f disruptin r displacement f fibrus materials [10]. n light f the results f this study, the authrs cannt recmmend scraping techniques fr the cllectin f extraneus fibres frm a fibrus surface. Cleaning practices and hygiene in the search rm play an imprtant factr in preventing cntaminatin prblems, even when taping is used as the recvery methd. deally, a search rm shuld be as clean as pssible frm cntaminant fibres, and therefre, the presence f material n the flr shuld be avided. Whether such cleaning steps include mpping r sweeping, this study fund n difference in terms f their ability t create airbrne cntaminatin. Wiping the examinatin table and the use f paper as 142

9 C ROUX, J HUTUNEN, K RAMPUNG and J ROBERTSON a dispsable table cvering were als efficient t prevent cntaminatin. Hwever, the mst imprtant practice relates t the use f prtective clthing during an examinatin. Our results shwed that fibres were capable f sticking t standard labratry cats in larger numbers than t plyprpylene suits, and that apprximately 20-25% f transferred fibres remained n the cat after ne hur (Figure 16). Fr these reasns, dispsable prtective suits shuld be preferred t traditinal labratry cats. f this cannt be achieved because f the cst incurred, labratry cats are acceptable. Hwever, it is crucial t change int a clean labratry cat befre each examinatin, and t have different cats fr different search rms. Alternative prtective suits, such as antistatic plyester cats, exist and are used in sme labratries. t wuld be wrthwhile t test them in future cntaminatin experiments. As Quality Assurance practice at the beginning f an examinatin, taping the bench and the frnt trs f the examiner wuld be beneficial in demnstrating that acceptable levels f cleanliness were btained befre perfrming the examinatin. The search rm design can als play sme rle in preventing fibre cntaminatin. Fr example, ne f the features f the search rms used in this study was the psitive pressure air cnditining system designed t minimise the pssibility f envirnmental cntaminatin ccurring within the search area. The purpse f the system is t mve air currents ut f the examinatin rm and thus prevent air currents, and any fibres they carry with them, frm entering the rm and pssibly cntaminating an exhibit. t was apparent that fibres were being swept, by the air cnditining, acrss the rm twards the drway in mst experiments. t can be argued that an uncntrlled mvement f air int the search rm equates t an uncntrlled mvement f airbrne fibres frm the general envirnment, thus ptentially creating fibre cntaminatin, especially when there is n dr r the dr is cntinuusly being pened and shut. Althugh a psitive pressure air cnditining system seems preferable, mre research needs t be cnducted befre ne can reach a definitive cnclusin in this respect. Cnclusins This study has brught a wider perspective n the issues affecting ptential fibre cntaminatin in frensic search rms. A number f cnclusins can be made fllwing the varius experiments. Fibre mvement was fund t be dependent n distance, with fibre ppulatins decreasing with increasing distance frm the garment examinatin area. The mvement f fibres seemed t mainly ccur during the examinatin, with very limited depsitin f material afterward. With the specific garments used in this study and their respective sheddability, cttn fabrics generated the highest number f cntaminant fibres, fllwed by wl, acrylic and plyester items. Cttn fibres were als fund t be airbrne fr lnger perids f time. The scraping methd f fibre recvery was fund t result in an increase in fibre ppulatins prduced, fibres being transferred t the examiner's clthing and a number f fibres exiting the search rm. n additin, the high number f fibres prduced by scraping f the cttn garment resulted in residual cntaminatin despite stringent cleaning practices. n cmparisn, taping prduced lwer fibre ppulatins and hence lwer cntaminatin risk. Therefre, taping is a mre acceptable methd f fibre recvery, during garment examinatins, when cnsidering cntaminatin issues. Based n the results f this prject it is unlikely that a cmpletely clean search rm can ever be btained, even with best practice cleaning techniques. Hwever, with prper precautins it is pssible t minimise the cntaminant fibre ppulatin, and the threat f truly prblematic cntaminatin. Best hygiene practice shuld include the use f tw physically separate and dedicated search rms, paper t cver the examinatin table, dispsable prtective suits, and mnitring the level f cleanliness by taping the bench and the frnt trs f the examiner befre perfrming an examinatin. n any case, the presence f small numbers f particular fibres in search rms means that extreme care shuld be taken when interpreting results invlving nly a few fibres. The use f large general examinatin rms fr trace evidence recvery cannt be recmmended as there will clearly be a much greater chance fr crss cntaminatin. This is als the reasn why it is risky t cmpare extraneus fibres frm unknwn surces fund n tw bjects when trying t determine whether cntact had ccurred. Acknwledgments The authrs wuld like t thank the staff f the Frensic Service - Australian Federal Plice, Canberra, fr their assistance during the experiments held in their labratry. The members f the Criminalistics Specialist Advisry Grup (SAG) f the Senir Managers f Australian and New Zealand Frensic Labratries (SMANZFL) are als acknwledged fr their participatin in the survey cnducted prir t this study. Mark Sandercck, Ryal Munted Canadian Plice, Winnipeg, is als thanked fr his suggestins during the preparatin f the manuscript. References 1. Rux, C, Langdn S, Waight D and Rbertsn J. The transfer and persistence f autmtive carpet fibres n she sles. Science & Justice 1999; 39(4): Gaudette BG. The frensic aspects f textile fibre examinatin. n: Saferstein R, ed. Frensic science handbk, VL 2. Englewd Cliffs: Prentice Hall, 1988: Grieve M. Fibres and their examinatin in frensic science. Frensic Science Prgress 1990; 4: Siegel JA. Evidential value f textile fibre-transfer and persistence f fibres. Frensic Science Review 1997; 9:

10 Factrs affecting the ptential fr fibre cntaminatin in purpse-designed frensic search rms 5. Rbertsn J and Grieve M. Frensic Examinatin f Fibres. 2nd editin. Lndn: Taylr & Francis, Grieve M. Back t the future - 40 years f fibre examinatins in frensic science. Science &Justice 2000; 40(2): Kaufman F. The Cmmissin n Prceedings nvlving Guy Paul Mrin. Ontari: Queen's Printer fr Ontari, 1998: MO<Je JE, Jacksn G and Firth M. Mvement f Fibres between Wrking Areas as a Result f Rutine Examinatin f Garments, Jurnal f the Frensic Science Sciety 1986; 26: Cxn A. Grieve M and Dunlp J. A Methd f assessing the fibre shedding ptential f fabrics. Jurnal f the Frensic Science Sciety 1992; 32: Rbertsn J and Rux C. Transfer. Persistence and Recvery f Fibres. n: Rbertsn J. and Grieve M. ed. Frensic Examinatin f Fibres. 2nd editin. Lndn: Taylr & Francis, 1999: