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Forensics

The Art of Fire Investigation Photo: Ian Peck

The examination of fires is perceived to be a difficult area of forensic science as fire destroys potential evidence which can determine how, when and where the fire started and by whom.

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28 CENTRAL LONDON LAWYER

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his perception is mirrored in the most recent statistics which indicate that deliberate fires are increasing yet the number of convictions are falling, currently the conviction rate is around 5%. There are a variety of reasons for this but part of the issue must lie with the way arsons are investigated both at the scene and away from it. If you are asked to work on an arson case it is always worth checking the credentials of the person that is reporting the evidence to determine whether they are a reliable witness and if their conclusions can be substantiated. Many criminal investigations are subject to cognitive bias and this is an area of particular weakness in fire investigation therefore alternative hypotheses should be fully explored and perhaps independently reviewed. There are a number of things to look for at fire scenes: • The worst area of burning normally denotes where the fire has started. • A short time delay between a person leaving a premises and a fire being discovered could indicate a deliberate act. • It is sometimes difficult to differentiate between a fire started by a flame and a smouldering ignition source, such as a cigarette, without timings information as the resultant damage could be the same. • Ignitable liquids such as petrol and white spirit can be used to ‘accelerate’ a fire, but it is their vapours not the liquid that is ignited. The differing chemical composition of these liquids give them differing properties and burning characteristics. • Hand rolled cigarettes tend to self-extinguish if they are not actively smoked. One of the major areas of discussion within the cause and origin determination of a fire is around the timings of a fire and what that means in terms of potential ignition sources. Flame sources such as dropped or applied matches and lighters coming into contact with combustible items can produce flaming fires within a matter of minutes. Fires started by lit manufactured cigarettes can progress to flaming but first they will smoulder, a glowing flameless fire, for at least 20 minutes and more usually several hours producing increasing amounts of smoke. Information from smoke detectors can assist as they will give an early warning to any type of fire. Therefore, if a flaming fire is seen within minutes of a smoke detector sounding then it is likely that the fire was started by a flame. Fire scenes are challenging and the remaining evidence can be interpreted in a number of ways, however not always accurately. If you would like some assistance from experts that specialise in fire investigation then please contact us.

Ian Peck Forensic Scientist

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Central London Lawyer May 2019  

The Official Law Journal for the City of Westminster Law Society. Featuring the latest news and features on International events, property a...

Central London Lawyer May 2019  

The Official Law Journal for the City of Westminster Law Society. Featuring the latest news and features on International events, property a...

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