Topic 2: arson

Question 1

define arson

Answer 1

• Arsonistheintentionalsettingofafiretoastructureorwildlandarea.
• complexcrimeanddifficulttoprove.
• extensivedestruction

Question 2

what is a fire?

Answer 2

• Rapidoxidationofamaterialinthechemicalprocessofcombustion.
• Producesheatandlight
• exothermicreaction

Question 3

what are the requirements needed for combustion to be initiated and sustained?

Answer 3

oxygen, heat and fuel (fire triangle)

Question 4

how to determine if the fire was an arson or an accident.

Answer 4

one or more of the components of the fire triangle was manipulated:
•increasethefuelloadbyaddingaccelerantorflammableitems. •Moreoxygenmaybeintroducedbyopening
windowsorpunchingholesinwallsortheceiling.

arson: intentional, multiple points of origin
accidental: e.g point of origin at electrical outlet

Question 5

what are some other clues of origin?

Answer 5

• Strangeodors
• Accelerantsoakedragswillkeepthefireloworlocalized,nottravelingupasusual
• Extensiveregionsoflowburn
• Fasterandhotterfirethanwouldbeexpected.
• Emptycontainersofaccelerants,timedelaydevices,andotheritemsleftbytheperpetrator.

Question 6

how does an arson start? what does it involve?

Answer 6

•Fireinvolvesaccelerant(substanceusedtoaidthespreadoffire)
andincendiarydevice(adevicethatisdesignedtocausefire)
toigniteit.

Question 7

what ais an accelerant? what are the 3 types of acclerants? give examples. what is the most common accelerant?

Answer 7

Accelerantisanythingthatisintentionallyplacedatascenetostartandsustainafire.
•Solid(wood,paper,roadflares),liquid(gasoline)orgas(naturalgas,propane)
•Gaseousaccelerantwillnotleavechemicalresiduesbutinstead there might bephysicalevidence(e.g containerusedtoholdordeliverit)

Themostcommonaccelerantsareliquidpetroleumdistillateproductssuchasgasoline,keroseneanddieselfuel.

Question 8

what are some examples of an incendiary device used to start fires?

Answer 8

•Startfireswithacigarette,matches,firearms,

electricalsparkandaMolotovcocktail(petrolbomb).

Question 9

what is the point of origin of a fire?

Answer 9

Placetolookfortracesofincendiarydeviceisthepointoforiginofafire.

Question 10

what are some tell tale residues of an arson?

Answer 10

(i)soapusedasagellingagenttoconvertaflammableliquidintoanapalm‐like(highlyflammablestickjellyusedinbombs)mixture),
(ii)characteristicashresidues(e.g.decompositionproductsofaflare’sfuelandoxidiser)
(iii)residuesofcommercialmaterials(e.g.thermite(amixtureoffinelypowderedAl
andironoxidethatproducesaveryhightemperatureoncombustion,usedinwelding/bombs),gunpowder)
(iv)flammablemetalsfire(e.g.Li,Ketc)

Question 11

what is reckless arson?

Answer 11

arson caused by reckless behaviour that leads to the destruction of property

Question 12

describe the general 4 steps in arson investigation

Answer 12

1. determinethecauseofafireandensuretheresponsibleparty
   isheldaccountable.
   Majorobjectivesofafireexaminationistherecognition,identification,and
   analysisoffirepatterns.

2.Anarsoninvestigationbeginswhenfirefightersarecalledtothesceneofafire.
3. specially trained arson investigatorsreviewthesceneandphysicalevidence,
andinterviewwitnessesaswellasfire‐fighters regarding their observations at the time of the fire.
4. a criminologist needs to detectandidentifyrelevantchemicalmaterialscollectedatthescene,
reconstructthecrimeandidentifydetonatingmechanisms.

Question 13

what is a sniffer? (device)

Answer 13

•Highlysensitiveportablevapourdetector
•Valuableaidatthefirescenehowever
theoperatormustbeawareoftheprincipleofoperationoftheinstrumentsothatitmaybetuned
correctlybeforeuseanditsresultsareinterpretedcorrectly.
•Aidforthecollectionofsamplesforlaboratorysubmissionandtheirresultsarenotconclusiveregardingthepresenceorabsenceofanaccelerant.

Question 14

what is a sniffer? (dog)

Answer 14

• Accelerantdetectioncanines/dogs(ADC)
• Conditionedtorecognizetheodourofhydrocarbonaccelerants.
• Trainedarsondogs&itshandler

Question 15

what are the 6 common fire patterns? what does a fire fire pattern indicate?

Answer 15

•ClassicV‐Shape •InvertedCone •ProtectedArea •CleanBurn •RunDownBurn •IgnitableLiquidPourPattern

Thefirepatternshouldindicatethepointoforiginorwherethefirebegan.

Question 16

how is arson evidence collected?

Answer 16

• Ashandsootdebrisshouldbecollectedfromthepointoforigin
• Sealedinanairtightcontainer(Metalarsonevidencecans).
• Debris is placed loosely in can, leaving plenty of headspace above.
• Airtight seal that traps vapours, including residual volatile accelerants .•Theairtightcontainerwillensurethatthevaporsdonotescape.
• Sampling of similar but uncontaminated sample as control

Question 17

what technique is used to analyse arson avidence? briefly describe the process.

Answer 17

GC
•Heat the airtight evidence container so that volatile residues will be driven off the collected material and trapped in the container’s headspace.

•Vapour is removed with syringe and injected into the GC.

Question 18

what are the 4 ASTM protocols for fire debris preparation?

Answer 18

1) E1385Steamdistillation
2) E1386Solventextraction
3) E1412Passiveheadspaceconcentration(absorption/elution)withactivatedcharcoal
4) E2154Solid‐phasemicroextraction

Question 19

briefly describe the process of steam distillation. what is effective and ineffective about this method?

Answer 19

•Firedebrisistransferredtoadistillationapparatus,andheatisapplied.
•Asit vaporises,theyarecooledandcondensed,droppingintoacollectionthimble.
•Anypetroleumproductsiscollectedasalayerontopofwater.

•Itiseffectiveinseparatingandconcentratingaccelerants,buttimeconsumingandmorevolatilecomponentscanbelost.

Question 20

briefly describe the process of solvent extraction. what is effective and ineffective about this method?

Answer 20

• Solventextractionofdebriswithpentaneandcarbondisulphide(CS2).
• Solventisaddedtotheevidence,collected&concentratedintoasmallvolume(about1‐5mL). •BothpentaneandCS2arenonpolarandwellsuitedtoextractpetroleumhydrocarbons,butbothalsohavelimitations.
• Pentaneisvolatile,caretakenthatsolventextractdoesnotgotodryness.Ifitdoes,lighterweightfractionswillbelostalongwiththepentane. •CS2 isnotvolatile,butitistoxicandhasafoulodour.
• Solventextraction,likesteamdistillation,canresultinalossofmorevolatilefractionsofresidualaccelerants.

Question 21

briefly describe the process of Passiveheadspaceconcentration(absorption/elution)with
activatedcharcoal. what is effective and ineffective about this method?

Answer 21

• Allheadspacemethodsinvolveconcentratingvolatilesintoasolidphasebyabsorption.
• Protocoliscalledtrapping,andinthecaseoffiredebris,trapismadeofcharcoal.
• Apolymerstripcoatedwithcharcoalisdangledabovefiredebrisandevidencecanberesealed.
• Gentleheatingdrivesvolatilesintovapourphase,fromwhichtheymovevia diffusiontothecharcoal,wheretheyareabsorbed.
• Attheendofheatingtime,charcoalstripisremovedand subjected toGCanalysis.

•Itisporous,thusrelativelylargesurfacearea&moreeffectiveextraction. •Inert&relativelycheap.

Question 22

briefly describe the process of Solid‐phasemicroextraction. what is effective and ineffective about this method?

Answer 22

• Theabsorbentsareusedtocoatthesilicaneedle.
• SPMENeedleisdirectlyintroducedintoGCforthermaldesorption,orsolventextraction
• Advantageisversatility,highsensitivity,solventless approach.
• Fiber canbeimmersedinanaqueousmatrixifthefiredebrisiswaterlogged.