Bodies From Fire Flashcards
Key features of fire dynamics
Started with spark Needs to burn - oxygen - heat - fuel
Phases of fire dynamics
Incipient - fuel supply heated and ready to burn Emergent smouldering - inefficient combustion -> smoke Growth of flames - efficient burning - intensity doubles for each 10°C rise in temperature - flashover ignition temperature of nearby combustible material is reached
Bodies from fire manner of death
Natural - cause - inability to escape Accident - most common - alcohol, drugs, cigarettes - clothing - electrical Suicide - rare in west - accelerant on clothes, car Homicide - rare as method except arson - concealment of homicide - often fails
Key investigation points for investigation of fire related deaths
Was the victim alive at start of the fire
What was the cause of death
- fire - CO, smoke, burns, heat shock
- other - natural, alcohol, drugs, homicide
Why was the victim in the fire
Why was the victim unable to escape
Features of identify a body
Circumstances Personal effects Fingerprints DNA Dental X-rays Operations - presence/absence of ovaries, womb and appendix
Investigation of fire related deaths
Medical hx Circumstances Fire investigators examination of the scene - origin, development, nature of f Autopsy Toxicology and laboratory investigations
Fire artefacts
Occur in any body from fire irrespective of cause of death Pugilistic posture - arms flexed at elbow and fist clenched - boxer position - flexion of hips and knees - flexors more powerful when all muscles shortened Post mortem burning - thin reddened margin - leathery brown from smouldering heat - charred by high temp or direct flame Hair singed and turns reddish-brown Skin becomes blistered or may shrink, tighten and split Heat fractures Heat haematoma - extradural - crumbly layer of altered blood Falling masonry Recovery of body - easily damaged during moving
Features of severe PM burning
Skin splits Skin loss Muscle loss Amputation of limbs Exposure of body cavities - chest - abdomen - cranial cavity
Features if deceased was alive at the start of the fire
Signs that victim was breathing - not necessarily conscious
- soot in airways below the level of the vocal folds
- thermal injury to larynx
- blood CO > 10%n
Absence of signs does not necessarily indicate already dead
Mechanisms in death in fire related deaths
Smoke inhalation - thermal injury to URT - CO - particulates - smoke poisoning - toxic gas Burns - depth - extent - ante mortem vs post mortem - burning continues post mortem - singing, carbonisation, charring
Features of thermal injury in smoke inhalation
- common
- URT very efficient heat exchange - LRT protected
- dry air > 150°C or moist air causes laryngeal injury
- breathing hot air may cause reflex vagal inhibition
- laryngeal spasm
- laryngeal oedema
- tracheobronchial necrosis seen microscopically
Features of carbon monoxide poisoning
Colourless and odourless
From incomplete combustion of fuel
Binds to Hb with 200x more affinity than 02
- diminishes o2 carrying capacity and dissociation
- toxicity depends on
- rate of inhalation - concentration of CO and duration of exposure
- physical activity
- individual susceptibility - heart, lung disease
- blood levels expressed as a % of Hb
Clinical effects are dose related
- 50% = fatal - varies by health and fire factors
- 30-40% = impaired judgement, failure to escape, LOC
- 20-30% = dizziness, SOB, headache, nausea, fatigue
- 10%+ indicates victim alive during fire
- level below 10 does not mean already dead
- little or no CO produced due to abundant O2 leading to CO2 production
- rapid death due to cardiac arrest
Signs of CO poisoning
Pink discolouration of conjunctiva
Bright cherry pink prominent lividity
Features of direct particulate injury
Superheated soot and other particulate debris passes deeper into URT than other gases Depth of penetration depends on size - >10um = to nares - 5-7um = to trachea and bronchi - 1-3um = reach alveoli Seen histologically
Features of smoke poisoning
Effect of CO and noxious gases - incapacitation and death - not routinely measured CO and cyanide commonly measure Other gases include - HCl - NO2 - aldehydes - benxene - ammonia - SO2 - phenol - acrolein
Causes of toxic gases
CO2 - all combustibles containing carbon NO2 - cellulose - polyurethanes - acrylonitrile HCl - PVC HCN - hydrogen cyanide - wool - silk - nylons - polyurethanes Aldehydes - wool - cotton - paper - plasters - wood - nylon - polyester resin Benzene - petroleum - plastics - polystyrene Ammonia - melamine - nylon Effects may be additive so that non-fatal levels of each in combination may kill
