Often times you hear about the cause of a fire being a cigarette for example. However, isn’t the cigarette already long gone after the house/forrest/etc. has burnt down? How is it still possible find out what started the fire?
In: 567
Burn patterns are different, and sometimes you can smell something characteristic, like gasoline. Identifying where the fire started can help (if it’s an ash tray probably it started with a cigarette). There are also chemical tests but I don’t know a lot of details.
Each fire has their own “signature” depending on the materials, any accelerants (such as gasoline), temperature and weather conditions, etc. Knowing *where* the fire started, from tracing the spread of the fire, gives clues as to what might have ignited the fire.
For example, let’s say there’s a house that burned down. Investigators may notice that certain parts of the house burned much more rapidly than others, indicating that someone might have intentionally poured an accelerant in the basement and set fire to it there as an act of arson.
Another example, specifically referencing the Kings Cross fire, might have a blaze starting under the escalators. Investigators were able to identify the combustible material beneath the escalator, combined with buildup of grease and oil, and recognised the commuters’ habit of disposing their cigarettes between the handrail and the gap in the steps.
While the cigarette is long gone, there are only so many ways a fire can start, and examination of the remaining evidence will narrow it down to something as small as an exposed wire or a burning cigarette.
*most* structure fires the houses are total losses where it burns down to the ground. Most areas, especially with those with professional paid departments, usually get the fire under control before it causes a total loss. These houses will general have lots of “clues” on what started the fire. Most house fires the houses are able to be rehabbed and used again.
The answer is things like chemical traces left at the site and burn patterns.
On the other hand 10ish years ago it came out that a significant chunk of arson analysis techniques had no real scientific backing or proof of any sort, like bite comparison turned out to be. It was quite a big thing for a bit that I lost track of.
I was once told newspaper is an effective accelerant that burns up entirely, unlike petroleum based alternatives
So, I’m not a firefighter but I work closely with them. I’ve spoken to fire investigators about determining cause and yeah like other ppl have said they have tools to look for accelerants and different chemical compounds and sometimes can figure out the general area of where it started but if it is a full burn and the house really gets trashed the answer is “youre S.O.L” in determining the cause
Religion and the Bible.
Naw I’m kidding it’s science like everything else. There are patterns after every burn and chemists/scientists who test samples from various places, and can find chemical signatures of arson (gasoline or lighter fluid, even matches) … it’s a whole science itself.
My Chief went to a convention where they literally take donated cadavers and burn them. They also have an extensive case database to reference.
They essentially study exactly what effects different kinds of arson have on a person.
Basically, if you try to dispose of evidence by burning a body, you’re going to get caught, lol.
The other answers are right, but it’s also important to ask another question.
Instead of “how do they know?” Ask “do they know?”
Because arson investigation suffers from the same confirmation bias that forensic investigation does. If you’ve kept up with forensic investigation over the past 20 years, you know that everything except DNA analysis has come under huge scrutiny for not having rigorous scientific guidelines. Blood spatter, bite mark, and hair analysis are now all considered junk science.
The fields of arson investigation and forensic science have similar origins. They were both largely driven by professionals in their fields (detectives and firemen) and not outside academics. Investigaters in both fields can suffer from the same pressure find a crime where sometimes there isnt one, and this can lead to a false interpretation of the data available. Many people have been convicted of violent crimes by junk forensic science, and smaller, but not insignificant number of people have also been convicted of arson when the actual culprit was faulty wiring or other accidental fire origins.
I took fire investigation, albeit for wildland fires. Most often fires don’t entirely incinerate the scene. In fact the fire is usually burning LESS intense at it’s point of ignition making the location of the start easiest to investigate. One can reconstruct the fire in many ways often by gauging the intensity of the burn which tells investigators how fast it was moving, if fuels were left behind, whether it had enough ventilation, if there were accelerants. You can often determine the direction of the fire’s movement based on soot deposits which remain on one side of a wire/fence and not the other.
Latest Answers