Forensic Support in Fire Forensic Support in Fire InvestigationInvestigation

Dr. Tom HanniganForensic Science Laboratory,

Garda H.Q.,

Phoenix Park,

Dublin 8,

Ireland.

Forensic Science LaboratoryForensic Science Laboratory

Agency of Dept of Justice, Equality & law Reform

Approximately 70 staff (all civil servants)4 sections; Biology, Chemistry, DNA,

DrugsFires dealt with in Chemistry SectionHoused in Garda Technical Bureau with

whom we work closely

Services to criminal Services to criminal investigationinvestigation

Identification of substances e.g. controlled drugs, explosives, accelerants in fire debris

Linking individuals and/or scenes to one another through– Biological– Impression or– Trace Evidence

How forensic science may link How forensic science may link individuals/scenesindividuals/scenes

Biological – biological fluid e.g. blood or cigarette butt at scene – DNA profile extracted– compared with profile of suspect.

Impression – fingerprints, footwear impressions, tyretracks, toolmarks.

Trace Evidence – anything that can be transferred e.g. fibres, paint , glass, firearm residue etc.

ExampleExample

Man wearing woolly jumper breaks into home of elderly person.

Breaks window, having first attempted to force open window with tool.

During violent assault, victim suffocates and dies.

Attempts to light fire but fire fails to take hold.

Examination of crime sceneExamination of crime scene

Window frame checked for fingerprints & fibres Control samples paint & glass taken Cast made of toolmark Clothing of victim taken at post-mortem. Suspect arrested – clothing taken for examination

for glass & fibres Tool in his possession examined for paint Marks made with tool compared with scene marks

Scene PreservationScene Preservation

Trace evidence lost with passage of time Forensic evidence usually delicate – avoid

disturbing Importance of preserving scene & limiting access Fire suspected to be malicious is a potential crime

scene DNA & Fingerprints can sometimes survive

extreme heat

Role of FSL in fire Role of FSL in fire investigationinvestigation

Mainly to assist in determining whether or not fire malicious

Done by analysing debris samples for hydrocarbon fire accelerants

Sanples must be taken from seat of fire Finding of accelerants, when unaccounted for, an

indicator of arson Must be interpreted in conjunction with other indicators Many other ways in which a malicious fire can be

started

Hydrocarbon Fire AccelerantsHydrocarbon Fire Accelerants

Main Classes:

Petrol White Spirit

Paraffin Oil Diesel Oil

All complex mixtures of hydrocarbons

Flammable & Volatile

If used to start fire, good chance that some of the heavier hydrocarbons will survive fire, perhaps by seeping into carpet & floorboards.

Packaging of debris samplesPackaging of debris samples

Proper packaging essential Debris samples should never be packed in paper

or plastic bags/containers (contamination) We recommend nylon bags for packaging debris

samples. Knotted or sealed & appropriately labelled Garda Scenes of Crime examiners have supplies

nylon bags

Analysis of hydrocarbon fire accelerantsAnalysis of hydrocarbon fire accelerants Analysed using Gas Chromatography (GC) A technique for separating chemical mixtures Debris sample is heated at 110C for 40 mins to

drive any accelerant residue into the vapour phase Sample of vapour from the bag drawn through a

glass tube containing Tenax, a polymer which adsorbs hydrocarbons

Tube placed in injection port of GC (325C) – hrdrocarbons driven off onto column and separated into individual components

Printout is a pattern of peaks characteristic of mixture

Fires: Gas ChromatographyFires: Gas Chromatography

• Flame ionisation detector

• Temperature ramping

• 30 minute run

• Tenax adsorbant

INPUTSYSTEM

SEPARATION SYSTEMDETECTION

SYSTEM

CHROMATOGRAPHY

FLOW

TIME

Diesel oil

Debris from scene

Other services (1)Other services (1)

Cans/continers liquid found near fire scenes–liquid analysed for accelerants–can sent for fingerprinting

Petrol Bombs (Molotov cocktails)-glass bottle petrol+wick; wick may provide forensic link e.g. with torn clothing in suspect’s house

Clothing & footwear persons suspected of handling acclerants-pack in nylon bags-avoid contamination-vapour lost rapidly

Other Services (2)Other Services (2)

Unburnt or partially burnt materials-basic flammability tests to determine whether or not material burns, how rapidly it burns

Electrical items – difficult to judge without visit to scene or access to comprehensive record of scene incl. photos. Can comment on signs of electrical activity in cable (arcing, fuse blown) or if device plugged in when fire started (smake pattern on plug).

ConclusionConclusion

Fire investigation is a multi-disciplinary exercise.

I hope this presentation has been helpful in clarifying the contribution of the Forensic Science Laboratory to the process.

Thank you for your attention.