a leave only fingerprints: student lab...

89Using Forensics: Wildlife Crime Scene!

Section 2: Training in Forensic Techniques

Name Date

Your JobMakeaninkcopyofyourfingerprintsandidentifypatterns.Inteams,makelatent(invisible)andvisiblefingerprintsonpaper,plastic,orglass.Afterex-changing mystery prints, use several forensics lab procedures to identifytheownersoftheprints.

Part 1: Make and Identify Your Fingerprints

1. Usingscrappaperandadark-coloredinkpad,practicemakingafinger-printwithaclearpattern.Here’showtodoit:

a.Lineuptheedgeofapieceofscrappaperwiththetopedgeofthetableinfrontofyou.Placetheentirefirstjointofeachfingerflatonthepaperwiththerestofyourhandhangingofftheedgeofthetable.

b.Lightlypressthefirstjointofyourthumbontheinkpad.c.TransfertheprintbyeitherpressingyourthumbstraightdownontothepaperusingtwofingersofyourotherhandandthenliftingstraightupORrollingyourthumbfromtheleftedgetotherightedgeusingyourotherhandforguidance.Youcanalsoworkinpairstoassisteachother.

2. Getafingerprintcard(Handout4-B)fromyourteacher.Youwillmakeasetofclearfingerprintsofbothhands.Here’showtodoit:

a. Foldthepaperunderthetoprowoffingerprintboxes.Theseboxesnowsitatthebottomofthevisiblepage.Placethisrowofboxesontheedgeofthetableinfrontofyou.

b. Usetheinkpadtomakeasetoffingerprintsonthefingerprintcardforonehand.Aftergettingteacherapprovalofyourprints,washyourhand.

c. Refoldthefingerprintcardunderthesecondrowofboxes.d. Makeasetoffingerprintsforthesecondhand.Aftergettingteacher-

approvalofyourprints,washyourhand.

3. Read“IdentifyingFingerprints”(Handout4-C)andanswerthe“WhatDoes It Mean?” questions at the end. Look at your own prints whilereading.Usethe“FingerprintPatternKey”inHandout4-C,pp.96–99,andmagnifyinglenstoidentifythepatternsforeachfinger.Writethepatternbeloweachprintonyourcard.

Handout 4-A

Leave Only Fingerpri

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Student Lab Investig

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Copyright © 2008 by the National Science Teachers Association. All rights reserved.

90 National Science Teachers Association

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Part 2: Prepare Mystery Fingerprint Evidence

1. Get a tray of required materials (rubber surgical gloves; 3" × 5" whiteandcoloredpaper;andsmall,fingerprint-freeobjectsthatyourteacherwillprovide)foryourgroupoffour.

2. Placethefingerprintcardsforallyourgroupmembersinthebottomofthetray.

3. Picktwogroupmemberstocreatevisible inkprintevidenceonpaper(#4below)andtwomemberstocreatelatentoilprintevidenceonglass,plastic,orcardboard(#5below).

4. Tocreatevisible inkfingerprintevidence:

a.Onepersonmakeinkprintsofyourthumbandpointerfingerfromeitherhandonapieceof3"×5" paper.Labelit“Evidence1.”

b.Thesecondpersonmakesinkprintsofyourthumbandpointerfingerfromeitherhandonasecond3"×5" paper.Labelit“Evidence2.”

c. Placethemysteryprintsinthetray.

5. Tocreatelatent oilfingerprintevidence:

a. Yourteacherwilltellyouwhichforensiclabtechniques(dustingpowder,superglue,oriodinecrystals)youwillbeusing.Ifyouwillbeusingthedustingpowertechnique,makeyourprintsonaglassjarorplasticpiece.Ifyouwillbeusingthesupergluetechniqueortheiodinecrystalstechnique,youcanuseglassorplasticmicroscopeslidesORpaperorcardboardpiecesthatfitintothefumingjars.

b.Putalatexgloveononehandbeforetouchingtheobjects.Pickupacleanobjectwithyourglovedhand.Holdonlytheedge.Markeachobjectas“Evidence#3”or“Evidence#4.”

c.Wipethefingersofyourotherhandacrossyourforeheadoralongthesidesofyournosetocoatthemwithbodyoil.

d.Carefullypressthefirstjointsofyourthumbandfirsttwofingersstraightdownontotheobject.Thenliftthemstraightup.

e. Placetheobjectinthetrayusingonlyyourglovedhand.f. Onaseparatepieceofpaper,recordwhoseprintsareonEvidence#1,#2,#3,and#4.Giveyourkeytotheteacher.





Part 3: Identify the Mystery Fingerprint EvidenceYourteacherwillletyouknowwhichforensiclabtechniques(dustingpow-der,superglue,oriodinecrystals)youwillbeusingtomakethelatentprintsvisible.

1. Exchangeyourtrayofevidencewithanothergroupandformtwopairswithinyourgroup.

2. Eachpairchoosesavisibleinkprintandalatentoilprinttoidentify.

3. Useamagnifying lens tocompare thevisible inkprints to thefinger-printcards.

4. Identifytheowneroftheprint.

5. Followthetechnique,specifiedbyyourteacher,formakingprintsvis-iblewithdustingpowder,superglue,oriodinecrystals.

6. Useamagnifyinglenstocomparetheprinttothefingerprintcards.

7. Identifytheowneroftheprint.

8. Checktheaccuracyofyourresultsbygettingthegroup’skeyfromtheteacher.

IfYouAreUsingtheDustingPowderTechnique,YouWillNeed:ButcherpapertocovertableFingerprintpowderorbabypowderFine,soft,andthickcosmeticpowderbrushesClear1"–2"cellophanetapeorpackingtape3"×5"paper(contrastingcolortopowder)Evidence:glassjarorplasticobject(contrastingcolortodust)

Procedure

1. Working inpairs,haveonepersonputonaplasticgloveandpickuptheglassorplasticevidence.Tearoffapieceofclear tape that is longenoughtoholdontotheedgesandstillcovertheprint.Becarefultonot

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addyourfingerprintstothecenteroftape.Hangtapefromtheedgeofthetabletouselater.

2. Lightlytouchthetipsofthebrushinthepowderandtapofftheexcess.

3. Lightlydusttheglassiteminacircularmotionuntiltheprintbecomesvisible.Thepowderwillsticktotheoilygroovesoftheprint.Becarefulnottodrowntheprintwithtoomuchpowder.

4. Whileonepersonholds theevidence, thepartnerneeds toattachoneedgeofthetapebeyondonesideoftheprintandrollthetapeovertheprint,beingcarefulnottomakecreasesorairbubbles.Thenheorsheslowlypullsoffthetapewiththetransferredprint.

5. Tapetheliftedprintsontopaperthatisdifferentfromthepowdercolor.Identifytheprintpatternandowner.

IfYouAreUsingtheSuperglue(Cynanoacrylate)Technique,YouWillNeed:SupergluetubeAluminumfoilAirtightglassjarsTweezersorsurgicalglovesWeakheatingsource(lamp,coffeecupwarmer,hotplate)SurgicalglovesEvidence:GlassorplasticmicroscopeslidesORpaperorcardboardpiecesthatcanfitintofumingjar.

Procedure

1. Blowintotheemptyfumingjartoaddhumiditytotheair.

2. Workunderafumehoodorinaventilatedarea.Putadropofsuperglueonasmallpieceofaluminumfoil.Usetweezersorsurgicalglovestoputthefoilinthebottomofthefumingjar.

3. Carefullyput thefingerprinted evidence in the jar so that itdoesnottouchthesuperglue.

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4. Closethelidtightlyandplacethejarbyawarmlamporonahotplateseton“low.”

5. Letthefumesfromthesupergluereactwiththeprintfor5–10minutes.Iftheprintisnotvisible,addeithermoreheatoranotherdropofsuper-glueandletsitforanother5minutes.Ifyouusetoomuchsuperglueorleavetheprintfortoolong,alayerofwhitewillhidethefingerprint.

6. Whentheprintisvisible,removetheevidencefromthefumingjarandidentifytheowner.

IfYouAreUsingtheIodineCrystalsTechnique,YouWillNeed:AirtightjarwithsmallamountofiodinecrystalsTweezersorsurgicalglovesEvidence:GlassorplasticmicroscopeslidesORpaperorcardboardpiecesthatcanfitintofumingjar.

Procedure

1. Pickupthefingerprintedevidencewithtweezersorsurgicalgloves.Iftheevidence isflatpaperorplasticandwillbehard togetoutof thefumingjar,attachittoapapercliponastring.

2. Work under the fume hood or in a ventilated area. Quickly open thefumingjarcontainingafewiodinecrystalsandputtheprintsinthejar.Letthestringhangovertheopeningontotheoutsideofthejar.Closethejartightly.

3. Lettheiodinefumesdeveloptheprintsforabout15minutes.

4. Underthefumehoodorinaventilatedarea,openthejar,removetheprint,andimmediatelyclosethejartightly.Identifytheowner.

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Name Date


Right Hand

Thumb 1st Finger 2nd Finger 3rd Finger 4th Finger

Classification of Print Patterns:

___________ ___________ ___________ ___________ ___________

Left Hand

Thumb 1st Finger 2nd Finger 3rd Finger 4th Finger

Classification of Print Patterns:

___________ ___________ ___________ ___________ ___________

Prints taken by: ________________________________________

Handout 4-B

Fingerprint Card




Name Date

Why is the search for fingerprintsat the scene of a crime so impor-tant?It’sbecauseeachpersonontheplanet has a unique set of prints,differentfromthatoftheotherbil-lionsofpeople.Evenidenticaltwinshave different fingerprint patterns.Afingerprint canprove that a cer-tainpersonwasat theplaceof thecrime or touched something thatwasusedinacrime.

Juan Vucetich, a Coatian-born Ar-gentine anthropologist and policeofficial,pioneeredtheuseoffinger-printingincriminalinvestigationsover100yearsago.In1891Vucetichbeganthefirstfilingoffingerprintsbased on ideas of Francis Galton,ideasthatheexpandedsignificant-ly.In1892,Vucetichmadethefirstpositiveidentificationofacriminalthrough the use of fingerprints.Two children had been murderedandtheirmotherhadreceivedsev-eral knife wounds, but survived.She accused a male acquaintanceof the crime, but a bloody fin-gerprint discovered at the sceneprovedtobeamatchtothemoth-er. Faced with the evidence, sheconfessedandwasconvictedofthecrime(NLB2006).Argentinepoliceadopted Vucetich’smethod of fin-gerprinting,anditspreadtopoliceforcesallovertheworld.

In1902,Dr.HenryP.DeForrestpio-neered the use of fingerprinting inthe United States. DeForrest led thecampaign to systematically finger-print all candidates taking the civilserviceexamfortheNewYorkCivilServiceCommission.Thisactionend-edthepracticeofpayingsomeonetotaketheexamintherealcandidate’splace. The following year, the NewYorkStatePrisonSystembeganfin-gerprintingallofitsinmates,andin1904theInternationalAssociationofChiefsofPolicecreated thefirstna-tional fingerprint collection site, theNationalBureauofCriminal Identi-fication (Sellin 1971). Today the FBIkeeps a computerized database ofover 49 million sets of fingerprintsforcriminals,civilians,militaryper-sonnel,andgovernmentemployees.

What Does the Forensic Scientist Need to Know?To analyze fingerprint evidence, aforensic scientist must understandthe anatomy of fingerprints andbe able to distinguish among themany fingerprint patterns. He orshe must also able to choose andconduct the most appropriate labtechnique to make a latent (invis-ible)printvisible.

Handout 4-C

Identifying Fingerpri

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Fingerprint Pattern KeyThereareeightfingerprintpatterns:plainarch,tentedarch,radialloops,ulnarloops,plainwhorl,centralpocketwhorl,doubleloopwhorl,andaccidentalwhorl. These patterns fall into three groups: arches, loops,andwhorls(Figure4.2).

Eachgrouphasadifferentnumberofdeltas,theplacewhereridgescon-vergefromthreesidestoformatriangleshape.Archeshavenodeltas,loopshaveone,andwhorlshavetwo(Figure4.3).

What Is a Fingerprint?A fingertip has small ridges andgroovesthatcreateauniquepattern.Thepurposeof theridges is tocre-ate friction between the fingertipsandtheobjectbeingtouched.

The skin is made of two layers (seeFigure 4.1). The outer epidermis iswornoffandreplaced throughoutalifetime. The inner dermis holds oilandsweatglandsthatkeeptheskinmoist. This oil pools in the groovesbetween the friction ridges. When afingertouchesanobject,theoiltrans-fersthepatternontotheobject.Thisoilprintcanbematchedtoafinger,andtothepersonwhomadeit.

Theridgepatternformsduringearlyfetaldevelopmentandneverchang-es. In the past, people have triedunsuccessfully to remove their fin-gerprints,butbecausetheridgesareindeeplayersoftheskin,permanentremovalofthemwoulddeformanddamagetheuseofthehands.


Handout 4-C


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4.2

Arch Loop Whorl

A. Hair

B. Epidermis

C. Dermis

D. Oil Glands

E. Hair Follicle

BA

C

D

E




ArchesArchesare thesimplestpat-ternsandhavenodeltas.Theridgesenterfromonesideofthefingerandexitontheop-positeside(Figure4.4).

PlainArch—Aplainarchmovesacrossthefingerwithnocenterpoint(core)orintersectingridges.TentedArch—Thecentercoreofthetentedarchlookslikeaverticalpoleholdingupatent,sometimesmistakenforadelta.

LoopsLoopsare themostcommonprintpattern.Aloophasridg-esthatenterandexitfromthesamesideofthefinger.Ithasonedeltaontheotherside.

Ifyouknowwhichhandtheprint was taken from, youcanclassifyitasaradial loop oranulnar loop.Placeyourrighthandpalm-downnexttotheloopsinFigure4.5.Iftheloopgoestowardyourlittle

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4.4

Tented arch

Arch (no delta)

Loop (1 delta)

Whorl (2 or more deltas)

Plain arch

4.5


finger(andulnarbone),itisanulnarloop.Iftheloopgoestowardyourthumb(andradialbone),itisaradialloop.Nowplaceyourlefthandonthepaper.Theulnarloopbecomesaradialloop,andviceversa.

WhorlsThecenterofawhorl looks likeacircle,or the ridgesmove inacircu-lardirection.Mostwhorlshavetwodeltas,thoughsomemayhavemore.Therearefourdifferenttypesofwhorls(Figure4.6).

PlainWhorl—Thecenterridgesformacircle,withlargercirclesmovingoutfromitlikeringsonalakeafterarockbreaksthesurfaceofwater.Ifanimaginarylineweredrawnbetweenthetwodeltas,itwouldcutacrossthoserings.CentralPocketWhorl—Thecentercircleofridgesisthere,butverysmall.Theouterridgesmovetoonesideofthepattern,causingittolooklikealoop.Ithastwodeltas,buttheimaginaryconnectinglinedoesnotcrossthecentercircles.DoubleLoopWhorl—Thiswhorlisactuallytwoseparateloopswrappedtogetherinthecenteroftheprint.Theyhaveseparateshouldersandtwodeltas.AccidentalWhorl—Thisuncommonwhorlisacombinationofdifferentloopandwhorlpatterns.Itusuallyhasmorethantwodeltas.

What Types of Fingerprint Evidence Are There?Therearethreetypesoffingerprintevidence:latentprints,visibleprints,andplasticimpressions.Thesetypesdescribethesurfacetheprintwasmadeonandhowtheprintwasmade.

Alatent print isamarkleftonasurfacefromthefinger’snaturaloil.Thistypeofprintisnotclearlyvisibleuntilanothermaterialtouches

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Plain Whorl Central Pocket Whorl

Double Loop Whorl

Accidental Whorl


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orreactswiththeoils.Themostcommonmethodtomakealatentprintvisibleistodustitwithpowderthatattachestotheoilsleftonthesurface.Iodinecrystalsandsupergluebothcausechemicalreactionswiththeoilsthatmakethelatentprintvisible.Lawenforcementagenciescannowusecomputerstodigitallyscanahandorfingertips.Avisible printcanbeseenwithoutanyadditionalhelpfromothermaterials.Itismadewhenafingertip—coveredwithpaint,ink,oil,dirt,cream,orothercoloredsubstance—touchesanothersurfaceandleavesamark.Plastic impressionsarethree-dimensionalprintsmadewhenafingerispressedintoasoftmaterialthatholdsitsshape.Impressionscanbemadeinclay,putty,grease,wetpaint,orsoftwax.

What Did You Discover About Fingerprinting?

1. Explainoneofseveralreasonspeoplebegancollectingandidentify-ingfingerprints.

2. Describeordrawtheanatomyofafingerprintusingthefollowingterminology:ridge, groove, oil, dermis, sweat gland.

3. Whatmakesafingerprintunique?

4. Howdodeltashelpidentifyaprint?

5. Whatisthemostcommonfingerprintpattern?

6. Whatarethedifferencesamonglatent,visible,andthree-dimension-alfingerprints?

7. Whatlabtechnique(s)didyouusetomakelatentprintsvisible?Whatworkedwellandwhatwouldyoudodifferentlynexttime?

8. ReadyourcommentsonfingerprintsinyourInvestigatorNotebook(What do I know about fingerprints? What do I want to know about finger-prints?).Respondtothefollowingquestion:What have I learned about fingerprints?

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Handout 4-C


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Sellin,J.T.1971.The police and the crime problem.NewYork:ArnoPress.

Wikipedia.n.s.http://en.wikipedia.org/wiki/Juan_Vucetich

Will waxing fingertips or fingertip surgery remove or mask a person’s fingerprints? Justify your answer.What can investigators conclude when fingerprints at a crime scene are matched to a specific individual?Why are fingerprints more effective than many other types of evidence at support-ing a person’s innocence or guilt in a crime?

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a leave only fingerprints: student lab...

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