Lethal smothering with a pillow

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Delft University of Technology

Lethal smothering with a pillow

How 181 music festival visitors tried to kill a dummy

Prinsen, Danique; van Dijke, Arjan; Horeman, T.; van de Berg, Nick; Loeve, Arjo J.

DOI

10.1016/j.forsciint.2020.110521

Publication date

2020

Document Version

Final published version

Published in

Forensic Science International

Citation (APA)

Prinsen, D., van Dijke, A., Horeman, T., van de Berg, N., & Loeve, A. J. (2020). Lethal smothering with a

pillow: How 181 music festival visitors tried to kill a dummy. Forensic Science International, 316, [110521].

https://doi.org/10.1016/j.forsciint.2020.110521

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Lethal

smothering

with

a

pillow

–

How

181 music

festival

visitors

tried

to

kill

a

dummy

Danique

Prinsen

a,b

,

Arjan

van

Dijke

b

,

Tim

Horeman-Franse

b

,

Nick

van

de

Berg

b

,

Arjo

J. Loeve

b,c,

*

a_University_of_Amsterdam,_Amsterdam,_The_Netherlands b

DepartmentofBioMechanicalEngineering,FacultyofMechanical,MaritimeandMaterialsEngineering(3mE),DelftUniversityofTechnology,Mekelweg2, 2628CD,Delft,TheNetherlands

c

CovanLedden-HulseboschCenterforForensicScienceandMedicine,Amsterdam,TheNetherlands

ARTICLE INFO Articlehistory: Received29May2020

Receivedinrevisedform13September2020 Accepted15September2020

Availableonline15October2020 Keywords: Smothering Forces Modusoperandi Pillow ABSTRACT

Purpose:Smotheringtodeathismostoftendonewithasoftcover,suchasapillow.Thisisoneofthe hardesttodiagnosecausesofdeath.Knowingmoreabouthowpeopleperformsuchanactandwhether thereisanycorrelationbetweenperpetratorcharacteristicsandsmotheringapproachesmayhelpin solvingcriminalcasesinvolvingsmothering.

Methods:Atotalof181visitorsofamusicfestivalwereaskedtosmotheradummywithapillow.Each participantprovidedtheirage,gender,dominanthand,length,weight,alcoholuse(last24h)anddrug use(last24h)inaquestionnaire.Forcesappliedbytheparticipantonthedummyheadwiththepillow werecontinuouslymeasuredandthesmotheringmodusoperandi(describedbyaspectssuchasthe placementofthehands,feetandbodyweight)wasobtainedfromvideorecordings.

Results:Participantswithhighalcoholconsumptionprovidedhighersmotheringforces.Increaseswere alsofoundfortallerparticipantsandthosewhohaduseddrugs.Smotheringseemedmosteffectivewhen placingbothhandsonthepillowontheheadandwhenplacingthecenterofmassasmuchdirectlyabove thedummyheadaspossible.Astable,centralstancealsobenefittedsmotheringeffectiveness. Conclusion:Forensiccaseworkmaypotentiallybenefitfromtheseresultsinthefuturebylinkingthe currentresultstothelocationofhandandfingermarksonapillow.

(http://creativecommons.org/licenses/by/4.0/).

1.Introduction

Smotheringtodeathisanoftenencounteredcauseofdeathin murder cases and is deﬁned as suffocation caused by an obstructionoftheairpassage[1].Insuffocationcasesitisoften hard to distinguish homicide, suicide and accidents based on physicaltraces.OfthemanypossibleMOs(modusoperandi)and materials, smothering with a soft cover (such as pillows, handkerchiefsortowels)isthemostcommonlyused,whilealso beingthemostdifﬁculttodiagnose[2].Typicalsmotheringvictims are infants, elderly, disabled, or people restrained by illness, alcohol or drugs. Because these victims are unable to defend themselveseffectively,trace evidenceisusuallyverysubtleand injuriesareoftenminor[2_–4].Fibersrecoveredfromthevictim_’s

mouth,noseorfacemayidentifytheobjectusedforsmothering, such as a pillow. The number of ﬁbers found may help to distinguish between criminal and legitimate actions (such as sleeping on a pillow) [5]. Hand and ﬁnger marks left on the smotheringobjectmayprovideinformationabouthowtheobject washandled[6,7].

DeRondeetal.[6]previouslyshowedinavolunteersstudythat thedistributionofhandandfingermarksiswell-distinguishably differentonpillowcasesaroundpillowsused forsmothering as compared to pillowcases only touched when changing the pillowcase.However,thesedatadidnotprovideanyinformation abouthowthevolunteersconductedthesmotheringintermsof pillowhandling,bodypositioningandpostureoramountofforce applied.Takingtheseaspectsintoaccountmayhelp_findingany relationsbetweensuspects’characteristicsandsmotheringforces and smothering MOs, which may eventually enable forensic investigatorsto determine from hand and _finger markshow a pillowusedforsmotheringwashandled,withhowmuchforceand perhapsevenbywhatkindofperson.Therefore,theaimofthis studywastoexplorewhatMOs,posturesandforcesareusedby

*Correspondingauthorat:DepartmentofBioMechanicalEngineering,Facultyof Mechanical, Maritime and Materials Engineering (3mE), Delft University of Technology,Mekelweg2,2628CD,Delft,TheNetherlands.

E-mailaddress:a.j.loeve@tudelft.nl(A.J. Loeve).

http://dx.doi.org/10.1016/j.forsciint.2020.110521

ContentslistsavailableatScienceDirect

Forensic

Science

International

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volunteersmimickingsmotheringandhowtheseaspectsrelateto volunteers’characteristics.

2.Materialsandmethods

At the music festival Lowlands 2016 (19_–21 August 2016, Biddinghuizen,theNetherlands)181participantswereaskedto simulate a smothering act with a pillow on a dummy. The experimentwascarriedoutbytheauthorsincooperationwiththe University of Applied Sciences (Amsterdam, the Netherlands), NetherlandsForensicInstitute (theHague,theNetherlands)and DutchPoliceAcademy(Apeldoorn,theNetherlands)andwasthe sameastheonefromwhich thedataofdeRondeetal.[6]was obtained as part of theLowlands Science experiments. Ethical approvalwasobtainedfromtheHumanResearchEthics Commit-tee(studynumber46)oftheuniversitytowhichthe correspond-ingauthorisafﬁliated.

Priortotheexperiments,participantswerebriefed,signedan informed consent form and filled in a digital questionnaire covering age, gender, dominant hand, length, weight, alcohol use(last24h)anddruguse(last24h).Nodatawerecollectedthat could lead to identi_fication of any of the participants. The participant next conducted two tests in randomized order in different rooms: smothering the dummy with a pillow and changingapillowcase.Thelatterwasusedtoinvestigateiffinger marksonpillowcasesusedfor smotheringcanbedistinguished fromthoseonpillowcasesonlyusedfornormalactivities,which wasdescribedelsewhere[6]andwillnotbediscussedfurther. 2.1.Testsetup

Inablindedroomadummy,sizedlikeanadultmale,waslaid faceuponasinglebed,withablanketandsheetcoveringitsbody (Fig. 1).Thebedwassituatedsuchthattheﬂoorspacewasequalon both sidesofthebed.Avideocamerarecordedthesmothering withouthavingtheparticipant’sfacevisible.Thedummyheadwas madetomovefreelywithrespecttothebodyandwasﬁxedona metalpinrunningthroughthemattressandbed.Themetalpin restedvia aspring (Fig.2)ona loadcell (FutekLCM300, 2kN, FUTEK Advanced Sensor Technology, Inc., Irvine, CA, U.S.A.). Contrary towhat is mentioned erroneously in de Ronde et al.

[6],nopressures,butonlyresultingverticalforcesonthedummy headweremeasured.Thesensorsignalswereampliﬁed(Scaime CPJ RAIL, SCAIME,Juvigny, France), converted to digital signals (Labjack U3-HV, Labjack co., Lakewood, USA) and sent to a measurementPCwithdataacquisitionsoftwarecustom-madein Matlab(Mathworks,Natick,USA).

2.2.Smotheringtestthresholds

Inrealsmotheringsituationsfullyblockingsomeone’sairways may require quite high forces, especially if the victim resists. Makingatestdummythatwouldstruggleinresistancewouldnot onlybecomplexandcreateamoredangeroustestsituation,but wouldalsohavebeendeemedunethicallyrealisticand possibly traumatic by the ethics board. Therefore, in order to make all participants putin considerableand a somewhat standardized

Fig.1.Overviewofthesetupusedforthesmotheringexperiment.Thewoodendummyheadrestedonaforcemeasuringunit,whichisdescribedinFig.2.

Fig.2.Forcemeasurementsetupusedtomeasuretheamountofforceexertedby participantsonthedummyheadwiththepillow.Adetailedspeciﬁcationofthe usedelectronicsisgiveninthetext.

D.Prinsen,A.vanDijke,T.Horeman-Franseetal. ForensicScienceInternational316(2020)110521

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effort during smothering a threshold force was set for the minimum force required to mimic blocking the airways. This thresholdwasdeterminedbyhavingtheleadinvestigator(victim) rest with his head on the pin of the dummy head. Another investigator(perpetrator)placedthepillowusedforthe experi-ments(seesection“TestProtocol”)onthevictim’sfaceandstarted pushingdowncarefullywithincreasingforce.Thevictimheldhis armup,holdingametalrodandloweredhisarmifhewasn’table tobreathe.Theforceatthatinstancewasnotedandtheperpetrator directlyremovedthepillow.Lettingthevictimholdthemetalrod was a safeguard to ensure that if he would faint this would instantlybenoticed.Anaveragethresholdforceof150Nwasset basedonthistest.

Afittingthresholdtimewassettoensurethatallparticipants would putin prolonged effort, which would often make them changepositionafterawhileorchangetheirsmotheringbehavior inordertobeabletokeepuptherequiredforce.Informationin web and dark web sources suggested that about 3.5min of smotheringwouldbenecessarytocommitmurderbysmothering witha pillow,while thetimerequiredforsmotheringa person untilunconsciousnessisabout5minaccordingtoothersources [8–10].Forpragmaticreasonsandbecause30soffierce smother-ing already proved tobe quite tiring in pilottests, a standard smothering time of 45s was chosen. In the experiment, all participantshadtoinputidenticalimpulses:45s*150N=6750Ns, soharderpushingresultedinalesserrequiredsmotheringtime and a quicker finished test. The user interfaceof the software continuouslyshowedandrecordedtheappliedforcesandimpulse andwarnedthetestsupervisorwithabrightlycoloredfull-screen messageiftheparticipantwaspushingundertheforcethreshold andthushadtobeencouragedtopushharder.

2.3.Testprotocol

Before each smothering test, the participant’s hands were washed,driedandthenpaintedwiththreeskin-compatible UV-paintcolors(PaintGlowNeonUVFaceandUVBodyPaint);blue (AA1B03) on the ﬁngers, pink (AA1B04) on the palms, yellow (AA1B01)onthethumbs(Fig.3).Theparticipantwasthenhanded acleanpillow(IkeaAXAG,6070cm,590gpillowinawashable hospitalpillow,6070cm,obtainedfrom https://www.zorgma-tras.com/waterdicht-kussen.html) in a clean black pillowcase (IKEA DVALA black, 6070cm, 100 % cotton, thread density 152)andinstructedtoenterthesmotheringroomandstandatthe footend ofthebed,received furtherinstructions andwas then allowedtostart.Participantswerefreetochoosefromwhichside

of the bed to approach the dummy head, where and how to positionthemselvesandhowtousethepillowforsmothering.

Participantsweretoldtokeepapplyingasmuchforceasthey coulduntilthetestsupervisorwouldindicatethattheyhadputin sufﬁcienteffort.Ifthetest supervisorreceiveda softwarealarm thattheparticipantwasnotpushinghardenough,theparticipant wasencouragedtokeeppushingharder.Oncetheparticipanthad input6750NsthesoftwareonthemeasurementPCindicatedthat thetestwascompletedandthetestsupervisortoldtheparticipant toletgoofthepillowbyleavingitwhereitis,removingtheirhands andsteppingawayfromthebed.Participantscouldcallforabreak iftheyfelttheneedtopause theexperiment,asksomethingor stop.Inthatcasethemeasurementsystemcouldbepausedand continuedlater.Thenumberanddurationofbreakswererecorded separatelybythesystem.

Theseparatedatasetsofeachparticipantwerecoupledusinga unique4-digitcodeonasetofidenticalbarcodestickers.Sucha stickerwasscannedtostartandlabelthequestionnaire,ﬁlmedat the start of the video, scanned to start and label the force measurements,stuckonthepillowcasestheparticipantusedand photographedtogetherwiththeﬁngermarksafterwards. 2.4.Datacollectionandanalysis

Thirtyvideorecordingswereanalyzedtoﬁndparametersthat could be used to categorize smothering MOs. Next, these parameters were extracted for all video recordings by authors DPandAJLindividually.Whenevertheseinvestigatorsproduced differentoutcomes,theirresultswerediscussedafterwardsand consensuswasfoundbyreviewingthevideosagain.Incasenotall parameters couldbe extracted fromthe videos because of the limitedviewofthecamera,thatparticipantwasexcludedfromall analyses.

Fromthemeasuredforcedataﬁvevariableswereobtainedand usedfromeachtestforfurtheranalysis,aslistedandexplainedin

Table 1. Data from the questionnaires was used to obtain

demographics and investigate any effects of participant’s sex, buildandalcoholordruguseontheirsmotheringforcesandMOs. Incaseoneormoreﬁeldsinthequestionnairewereleftblank,that participant was excluded from all analyses. Questionnaire and forcedatawerestatisticallyassessedinSPSS(IBMSPSSstatistics 25) using univariate general linear modelling (GLM) with a signiﬁcancelevel(p)of0.05,asitcandetectlinearandnon-linear relationshipsbetweenvariablesandisrobustforunequalgroup sizes.ThefactorsusedforGLMtestingwereF_mean,F_maxand t_smother.Becauseofthechosensmotheringeffort standardiza-tion,F_meanandt_validwereinverselyproportional:theirproduct was always about 6750 Ns (with round-off and timing errors causing minor variations). Therefore, F_mean was used in the statistical analysis, as this is the driving variablemost directly dependingontheparticipant_’sbehavior,andt_validwasleftout. The Kolmogorov Smirnov test was used to test the data for normality.

3.Results

Atotalof181participantstookpartintheexperiment.During the video analysis, 29 were excluded, leaving 152 for further analysis:

Sixwereexcludedbecausesomeofthelinkeddatawasmissing (whichhappenedifaparticipantforgottofillinthe question-nairefirst,didfillinthequestionnairebutdecidednottopartake inthesmotheringtest,orifthevideocamerawasn’tturnedon); Fourteenwereexcludedbecauseoneormoreparametersoftheir

smotheringMOcouldnotbeseeninthevideorecordings;

Fig.3. ResearcherapplyingUV-painttothehandsofaparticipant:pinkonthe palms,blueontheﬁngersandyellowonthethumbs(Forinterpretationofthe referencestocolourinthisﬁgurelegend,thereaderisreferredtothewebversionof thisarticle).

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Three were excluded for missing gender information in the questionnaire;

Sixwereexcludedafterbeingidentiﬁedasunrealisticoutliersin theforcedata:

oOneparticipantcouldnotkeepuptheforceandhadtopause, butthetestoperatorforgottopausethemeasurement,causing thetimedatatobe_ﬂawed;

oDuring analysis of the force data, the data of two participantswithtoolittleforceorstaminawereexcluded for being outliers with exceptionally long smothering times;

oThreeotherswereexcludedforbeingoutlierswith exception-allyhighmeanormaxforcesduetogivingshort,hardblowsto thedummyhead,causingimpactcontactpeakforcesonthe force sensor, preventing measuring the actually applied smotheringforce.

ThefulldatasetisprovidedinAppendix1asanoverviewof the included data and as a data file, complete with all excluded data, the used questionnaire and all briefing and debriefingformsin[11].Table2 showsthecharacteristicsof theincludedparticipantsasobtainedfromthequestionnaire. Participants’agesrangedfrom18to62years(mean27.8,STD 8.2). All data showed to be not normally distributed, but skewed(Fig.4).

3.1.Smotheringforces

Table3providesthedescriptivestatisticsofF_meanandF_max formales,femalesandallparticipantsgrouped.Asparticipantshad

Table1

Smotheringforceandtimevariablesmeasuredforanalysis. Variablename Explanation

t_smother[s] Runningtimefromthestartofsmothering(ﬁrstmeasuredforce)totheendofsmothering(lastmeasuredforce),excludinganyeventuIalbreaks. t_valid[s] Timeofvalidsmotheringabovethethresholdof150N

F_mean[N] Meansmotheringforceabovethethresholdof150N F_max[N] Maximumsmotheringforce

Eff_smother Thesmotheringefﬁciency;ratiobetweent_smotherandt_valid.

Table2

Studypopulationcharacteristics.

Category Number Gender Male 73 Female 79 Handedness Left 23 Right 129 Length[m] 1.51–1.60 6 1.61–1.70 38 1.71–1.80 56 1.81–1.90 37 1.90–2.00 15 Weight[kg] <60 20 61–70 49 71–80 34 81–90 23 91–100 16 >101 10

Alcoholuseinpast24h[glasses]

0 18 1–5 58 6–10 42 11–15 21 15+ 11 Noanswer 2

Druguseinpast24h

Yes 36

No 116

Fig.4.ProbabilitydensitiesforA)runtimes(trun),smotheringtimesabovethe smotheringthreshold(tvalid)andtotalsmotheringtimes(tsmother)andB)maximum (Fmax)andmean(Fmean)exertedsmotheringforce.

Table3

Smotheringforcesfortotalstudypopulationandpergender.

Total F_mean F_max

Totalstudypopulation(N=153)

Mean[N] 247 317 Median[N] 231 302 Std.Deviation[N] 703 997 Minimum[N] 157 177 Maximum[N] 433 602 Males(N=74) Mean[N] 254 316 Std.Deviation[N] 751 1009 Females(N=79) Mean[N] 241 317 Std.Deviation[N] 654 994 D.Prinsen,A.vanDijke,T.Horeman-Franseetal. ForensicScienceInternational316(2020)110521

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Table4

SmotheringMOaspectsextractedfromtheobservationvideos.Foreachaspect(leftcolumnboldtype),thecodesusedinthedatatablestomarkdifferentvariantsare providedinbolditalictypebetweenbracketsaftertheexplanation.Photosusedtoillustratesomeoftheaspectsarevideostillsfromtheexperimentrecordings.

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to push beyond the 150N threshold, F_mean was above this thresholdforallparticipants.

3.2.SmotheringMOs

Fromthevideodatasevenaspectswereestablishedtodescribe thecharacteristicsofthesmotheringMOsofallparticipants(See

Table4).Duringtheexperimentstheaspects‘Approach–side’and ‘Body–placement’appearedtobepotentiallybiasedduetothe locationwherethetestsupervisorandequipmentweresituated. Despiteensuringthesameamountofspaceoneachsideofthebed, havingtheparticipantsalwaysstartatthefootboardofthebed, and explicitlyinstructingallparticipantsthat theywerefreeto choosetheirapproach,onlysixparticipantschoosetheright-hand sideofthebed.Furthermore,theaspect‘Hands–switching’varied much between participants, did not show many consistent grouping options and mainly seemed to be an indicator for difficultyofgettingapropergrasp,ofgettingastableposition,orof finding and keeping up sufficient force. Therefore, these three aspectsareprovidedinAppendix1and[11],butwereleftoutof thestatisticalanalysisforthisreport.

Fig.5showstheparticipants’smotheringMOsdescribedbythe aspects ‘Legs– placement’,‘Hands – mainplacement’,‘Arms – posture’and‘Bodyweight–position’.InAppendix2acrosstabis providedshowinghowoftenwhichcombinationsofMOsoccurred asanoverviewandasa dataﬁlein[11].Themajority(87%)of participantshadatleastonefootnexttothebed.Standingwith bothfeetnexttothebedwaspreferredbyabouttwiceasmany women as men, while almost twice as many men as women preferredleaningwithonekneeonthebed.Havingatleastone kneeonthebeddidshowtoprovidebetterbodyweightplacement overthedummyhead.

Slightlymoreparticipantschosetoputbothhandsonthehead (OHOH) than both hands next to the head (NHNH) during smothering. Onlya smallminority usedone handon and one hand next to the head (NHOH). In this group, 12 out of 15 participants used their preferred hand to push on the head (Table5).ParticipantsusingtheNHOHplacementalwayshadat leastonefootplacednexttothebed.Byfarthemostparticipants appliedthesmotheringforcemainlywithstretchedarmsanda minorgroupusedmainlybentarms.

3.3.Relationsbetweensmotheringforceandtimeandother parameters

Theeffectsofthetestedfactorsobtainedfromthesurveyand testedsmotheringMOaspectsthatshowedtobesignificantare describedbelow.Fig.6aillustratesthesignificanteffect(p= 0.01) ofalcoholuseonF_mean,withhighconsumptionleadingtohigher force.Similarly,tallerparticipantsandparticipantswhohadused drugsshowed asignificantlydecreased t_smotherdue tohigher smotheringforces(Fig.6bandc).Nostatisticallysignificanteffects ofanyofthetestedvariablesonthesmotheringefficiencywere found.

F_mean,F_maxandt_smotherweresigniﬁcantlyaffectedbythe aspects‘Hands–mainplacement’(p<0.001forallthreevariables) and‘Bodyweight–position’(p<0.001forF_meanandF_maxand p=0.010 for t_smother). Forces were highest when both hands wereplacedontheheadandlowestwhenbothwereplacednextto the head,which logically resultedin theinverse for t_smother (Fig.7).Thecloserthecenterofweightoftheparticipant(located intheabdomen)waspositionedtobeingstraightabovethehead, thehighertheappliedsmotheringforceswereandthequickerthe smotheringwascompleted.Legplacementwitheitherbothlegs next tothebed ortwo kneesonthebed occurredwithhigher maximumforcesthanwhenonelegwasplacednexttothebedand onekneeonthebed.

Fig.5. DistributionofthedifferentsmotheringMO’sappliedbytheparticipants.A) Placementoftheparticipants’legs.‘Foot’indicatesafootplacedontheﬂoorand ‘Knee’indicatesakneeplacedonthebed.B)Placementoftheparticipants’hands. ‘Mixed’indicatesthatonehandwasplacedonthedummyheadandonewasplaced nexttothedummyhead.C)Postureoftheparticipants’arms.D)Positioningofthe participants’bodyweights,describedbyindicatingwhichbodypartwaspositioned mostdirectlyabovethedummyhead.

Table5

Handednessversushandplacedonthedummyheadofparticipantswhoplacedone handonandonehandnexttothedummyhead.Italictypeindicatesthatthe non-preferredhandwasplacedonthedummyhead.

ParticipantNr. Handedness Handonhead

2089 Right Right 2100 Right Right 2138 Right Right 2172 Right Right 2014 Right Right 2101 Right Right 2129 Right Right 2157 Right Right 2169 Right Right 2171 Right Right 2025 Right Right 2057 Left Right 2062 Right Right 2206 Right Left 2242 Right Left

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4.Discussion

Theresultsfromthepresentedexperimentsprovidedinsightin the MOs and exerted force of volunteers simulating forceful smotheringwithapillow.Thealcoholintakeoftheparticipants seemedtostimulatetheapplicationofhighersmotheringforces. This might be explained by a reduction of self-control due to alcoholintake.Theintakeofdrugsalsoshortenedthesmothering time, suggesting that drugs had a similar effect as alcohol. Unfortunately, the participantswerenot asked tospecify what kindofdrugshadbeenused.Therefore,noconclusionscouldbe drawn aboutany differencesin effectsbetweenstimulants and

depressants.Furthermore,noconclusionsaboutinteractioneffects betweenalcoholanddrugscouldbedrawn.

Larger participants required less time to complete the smothering,whereas nosigniﬁcant effectof weightwas found. Thismightbebecauseitwaseasierforlargerparticipants,dueto their larger reach, to position their center of mass above the dummyheadandusetheirweightmoreeffectively.Placingthe body weight as much over the head as possible proved most effectiveinapplyinghighsmotheringforces.Furthermore,leaning ontwofeetortwokneesprovidedhighermaximumforcesthan whenhavingonekneeonthebedwhilekeepingonefootnextto thebed.Thispossiblywasbecauseofimprovedbalanceandcenter ofmassplacement,butcouldalsoberelatedtothefactthatsome participantsputthelegnexttothebedbackwardsorevenoffthe ﬂoorwhenleaningwithakneeonthebed.Thelatterwouldcreate acountermoment,reducingthebodyweightonthehead.

Althoughcarewastakentokeepidenticalspaceonbothsidesof thebed,participantstended toavoidtherightside ofthebed, possiblybecausethatiswhere themeasurement computerand supervisorwere.Althoughtheavailablespaceleftfewoptionsto

Fig.6. Boxplotsforfactorsqueriedinthequestionnairethathadasigniﬁcanteffect onthesmotheringtime ormeansmotheringforce. Middlelinesindicatethe medians,theboxesspanthe25thto75thpercentiles,thewhiskersindicatethe range of the data and circles indicateoutliers. A) Alcoholuse versus mean smotheringforce.B)Lengthversussmotheringtime.C)Druguseversussmothering time.

Fig.7.BoxplotsfortheMOcharacteristic‘Hands–mainplacement’showingthe signiﬁcanteffectofthesubjects’handplacementmainlyonthedummyheadduring smotheringonA)meanandmaximumsmotheringforcesandB)smotheringtime (tsmother).Middlelinesindicatethemedians,theboxesspanthe25thto75th percentiles,thewhiskersindicatetherangeofthedataandcirclesindicateoutliers. HandsplacementvariantsareindicatedbyNH(bothhandsnexttothedummy head),NHOH(onehandnexttoandonehandonthedummyhead)andOH(both handsonthedummyhead).

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nothavethemeasurementcomputerinthesameroomasthebed infutureexperiments,itwouldbeadvisabletoputanyequipment in line with the bed to avoid participants from being biased. Furthermore, the viewfrom the single camera was blocked in several tests, leading to exclusion of these data. Adding extra camerasfordifferentviewpointswouldhaveimprovedtheviewon theexperimentsandwouldhavemadeestablishingtheMOmuch easier. However, in the current experiment full and easy-to-achieveanonymityofthesubjectswaspreferredoverhavingbetter videorecordings.Onlyoneparticipanttriedtoapplysmotheringby placinghisarmaroundthedummyheadandpressingthepillow onthedummyface (burking).Althoughthisis knowntobean effectivesmotheringMO,theparticipantwasaskedtoremovehis armfrombehindthehead,becausetheconstructionofthetest setupdidnotallowmeasuringanyforcesiftheheadwasn’tpushed upon. Becausenoothersubjectsattemptedthis MO, thisdidn’t affecttheoutcomeoftheexperiment.

Theappliedsmotheringthresholdof150Nwasbasedontests onasingle,healthy,1.74mtall,70kgweight,malesubject.This threshold was thereforerather arbitraryand maydiffer among victimsandmaybeparticularlydifferentforelderly,infantsandill, allergicorasthmaticvictims.Fortheexperiment,thesmothering scenario was designed as realistic as was possible within the boundaries of the situation: shortduration, minimal chance of adverse psychological effects, fully anonymous. In a real life situationavictimismorelikelytostruggleforsurvival,whilethe dummyobviouslyprovidednoresistance.

The actual time required for smothering a person until unconsciousness is about 5min [8–10], although bradycardia can occurafter 30s and ECG flattening starts at about90s, or soonerifmuchoxygenisconsumedbyheavilyfightingback[12]. Inthetestsonlyupto45sofsmotheringwasrequired,andusually less (Fig. 8). Yet, this did already deliver valuable results: the variationofMOsappliedduringsmothering,theforcevariations and theirrelationstoparticipantcharacteristics.Nonetheless,if longersmothertimeswouldhavebeenrequiredorifthedummy was somehow made to fight back, more participants may eventually nothavebeen abletocompletethesmothering due to fatigue or lack of strength, more MOs might have been alternated within a single participant’s attempt, and someyet undiscovered smothering MOs might have been revealed. Of coursethelackofastrugglingvictimdoesmakethecurrentresults unlikelytofullytranslatetocaseswithhealthy,consciousvictims. However,themajorityofsmotheringvictimsareknowntobetoo young,oldorweaktoresist[12–14].Yet,eveninresistivevictims thecurrentlyfoundMOswouldstillbeexpectedtooccur,possibly amongstothers.Tocheckwhetherlongersmotheringtimeswere primarilycausedbylowerforcesorbyincreaseddurationofthe moments thatsmotheringforceswerebelowthethreshold,the

smothering efficiency Eff_smother was calculated as t_smother/ t_valid. However, none of the MOs or questionnaire variables showedtohaveastatisticaleffectonEff_smother.Thismaysuggest thatlongersmotheringtimeswereinfactcausedbytheexertionof less force. Another explanation might be that the requested smotheringtimesweretooshorttoallowfindinganyexhaustion effects,eventhoughseveralsubjectscouldalreadybarelykeepup the requiredforce. Because theefficiency variations werevery small,nofurtheranalysesoninteractioneffectsweredone.

Therewereratherlargedifferencesingroupsizesinsub-groups ofparticipantsofdifferentage,height,weight,druguse,alcohol use and preferred hand. More equal group sizes would have allowedformorerobuststatisticaltestingandmighthaverevealed effectsthatwerenowleftundiscovered.Thequestionnairewould haveprovidedmorecompleteinformationifthetypeofdrugsused hadbeenaskedfor(depressantsversusstimulants).Furthermore, information about disabilities or diseases possibly affecting participants’ strength or stamina couldhave been valuable for moredetailedinterpretationofthedata.

DifferentsmotheringMOsmayleavedifferenthandandﬁnger markson differentlocations onthe pillowcase. Combining the obtaineddatawithinformation aboutthelocation ofhandand ﬁngermarksleftonapillowcase[6]mayhelptobetterinterpret traces left on a pillowcase that has possibly been used for smothering.

5.Conclusions

Atotalof181musicfestivalvisitorsusedapillowforsimulated suffocationofavictim, withthedataof 152beingincludedfor analysis. Thisprovided detailed knowledge abouttheMOs and forcesappliedbyparticipantsofvariousbuildsandages during smothering. Furthermore, the results suggested that drug and alcohol intake had stimulating effects on the fierceness of smothering.Fromthevideo observationdataitwas established whichMOswereusedandwhichparticipantposturesseemingly helped to speed up the smothering. After linking the current resultstothelocationofhandandfingermarksonthepillowcases in the future, the combined information might help forensic investigatorstoknowmorepreciselywheretolookfortraces,to establishoffenderprofiles,tolinksimilarcases,tocheckthestories ofsuspectsandtohelpestablishthechainofeventsinsmothering cases,particularlyincaseswherevictimscouldnotfightback. Funding

Thisresearchdidnotreceiveanyspeciﬁcgrantfromfunding agenciesinthepublic,commercial,ornot-for-proﬁtsectors.The cost of the authors’ participation in the research and of the equipmentwerecoveredbytheDelftUniversityofTechnology. Ethicsapproval

ThisstudywasapprovedbytheDelftUniversityofTechnology HumanResearchEthicsCommittee(studynumber46).

Consenttoparticipate

All participants signed an informed consent form for their anonymousparticipation.

Consentforpublication

All participants signed an informed consent form for the publication of the anonymous data gathered during the experiments.

Fig. 8.Smotheringtime above thesmotheringthreshold (tvalid)versusmean smotheringforceexertedbysubjectsonthedummy(Fmean).Eachdotrepresentsa subject.

(10)

Availabilityofdataandmaterial

Thefulldataset,informedconsentanddebrieﬁngforms,and theusedcustomdataacquisitionsoftwareareavailableathttp:// doi.org/10.4121/uuid:36ca19b5-18a7-41be-9387-dc9b3127de61. Codeavailability

Acquisition software has been published together with the dataset.

CRediTauthorshipcontributionstatement

DaniquePrinsen:Methodology,Datacuration,Formalanalysis, Writing-originaldraft,Writing-review&editing,Visualization. Arjan van Dijke: Methodology, Software, Resources, Project administration, Investigation, Writing - review & editing. Tim Horeman-Franse:Methodology,Resources,Investigation,Writing - review &editing. Nick van de Berg: Methodology,Software, Investigation,Writing-review&editing.ArjoJ.Loeve: Concep-tualization, Methodology,Software, Validation, Formal analysis, Investigation,Writing-originaldraft,Writing-review&editing, Visualization,Fundingacquisition,Supervision.

DeclarationofCompetingInterest Notapplicable.

Acknowledgements

The authors would like to thank Craig Appleby,Marcel van Beest, Marc van Bochove, Sander Ernst, Frits de Haan, Eef Herregodts, Anneke Koster, Roxy van de Langkruis, Mathilde Scheulderman, Beth Selway, Elmarije van Straalen and Roel Zaremba fortheirhelp inpreparingandconductingthe experi-ments.ManythankstotheorganizationofLowlandsforallowing us to partakein Lowlands Scienceand toChristianne dePoot, Marcel de Puit, Anouk de Ronde and Ward van Helmond for inviting ustotheteam,for theirinitialdraftoftheexperiment design,fortheircooperationinfurtherreﬁningandrealizingthe experiment, and for providing the bed, pillow,pillowcases and dummybody.AlsomanythankstoMaritvanVelzen,Jeroenvande VenandBasKraneveldoftheJeroenBoschhospitalfordonating

the computer systems used in the experiments and to Fien Bosman,JennyDankelman,RoyMeijerandDirkJanVeegerfortheir ﬁnancial and organizational support and for their support in handlingallthemediaattentionduringtheexperiments. AppendixA.Supplementarydata

Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j. forsciint.2020.110521.

References

[1]A. Sauvageau, E. Boghossian, Classiﬁcation of asphyxia: the need for standardization,JournalofForensicScience55(5)(2010)1259–1267,doi: http://dx.doi.org/10.1111/j.1556-4029.2010.01459.x.

[2]A.Schmeling,T.Fracasso,F.Pragst,M.Tsokos,I.Wirth,Unassistedsmothering inapillow,Int.J.LegalMed. 123(2009)517–519,doi:http://dx.doi.org/10.1007/ s00414-009-0362-7.

[3]S.JungJang,J.HyeokPark,Y.JooKim,S.HoonHam,N.YoungJo,H.Ha,Deathby homicidalsmotheringusinghotsteamtowel:acasereport,KoreanJ.Leg.Med. 37(2013)90–92,doi:http://dx.doi.org/10.7580/kjlm.2013.37.2.90.

[4]J.W.Osterburg,R.H.Ward,CriminalInvestigation-aMethodfor Reconstruct-ingthePast,RoutlegdeTaylor&Francisgroup,NewYork,2014.

[5]M.Schnegg,M.Turchany,M.Deviterne,L.Gueissaz,S.Hess,G.Massonnet,A preliminary investigation of textile ﬁbers in smothering scenarios and alternativelegitimateactivities,ForensicSci.Int.(2017)165–176,doi:http:// dx.doi.org/10.1016/j.forsciint.2017.08.020.

[6]A.deRonde,M.vanAken,M.dePuit,C.dePoot,Astudyintoﬁngermarksat activitylevelpillowcases,ForensicSci.Int.(2019)113–120,doi:http://dx.doi. org/10.1016/j.forsciint.2018.11.027.

[7]J. Fraser,K.Sturrock, P. Deacon,S. Bleay,D.H. Bremner,Visualisation of ﬁngermarksandgrabimpressionsonfabrics.Part1:Gold/zincvacuummetal deposition,ForensicSci.Int.208(2011)74–78,doi:http://dx.doi.org/10.1016/j. forsciint.2010.11.003.

[8]AirPollution,APHPublishing,NewDelhi,2005,pp.241.

[9]A.Scheiber,TheHumanComputer,Indiana,iUniverse,2002,pp.136. [10]I.A.Serlin,WholePersonHealthcare:Psychology,Spirituality,andHealth,

PennsylvaniaStateUniversity,Praeger,2007,pp.290.

[11]A.J.Loeve,D.Prinsen,A.P.vanDijke,T.Horeman-Franse,N.J.P.vandeBerg, Forcesandmodioperandiof181musicfestival(Lowlands2016)visitors smotheringadummywithapillow,4TU.CentreforResearchData(2020),doi: http://dx.doi.org/10.4121/uuid:36ca19b5-18a7-41be-9387-dc9b3127de61 [DATASET].

[12]V.J.M.DiMaio,D.M.DiMaio,M.Dembo,H.Seli,"Asphyxia,"ForensicPathology, CRCPress,BocaRaton,2001,pp.229–244.

[13]C.Schyma,B.Madea,Commentsonunassistedsmotheringinapillow,Int.J. LegalMed.125(1)(2011)155–156, doi:http://dx.doi.org/10.1007/s00414-009-0409-9.

[14]S.Banaschak,P.Schmidt,B.Madea,Smotheringofchildrenolderthan1yearof age—diagnosticsigniﬁcanceofmorphologicalﬁndings,ForensicSci.Int.134 (2)(2003)163–168,doi:http://dx.doi.org/10.1016/S0379-0738(03)00135-X.