Question: evaluate how a dead body would react if set alight and how would you find out causes of death and other facts about it? I know that you investigate car crashes so I guess dead bodies is your area

Mark Hill answered on 22 Mar 2011:

Hello Jackalope1997,

Hmm. This is partly in my field and partly in some others, especially Niamh’s discipline.

The human body has a high proportion of fat, which burns well. This is a suitable fuel load, providing there is an accelerant, or sufficient direct heat to assist combustion. The body fat has a fairly high ignition point but, once started, tends to burn thoroughly.

When a body burns, the muscles and connective tissues tighten and shrink. Think about the Sunday roast. It goes into the oven much larger than it comes out.

As with any onbject, its surroundings, what it is in contact with, may mask the degree of burn that it undergoes, even without intervention tomextinguish it. Thus, in a car, even with accelerant, such as petrol, or lighter fluid, areas of the body masked by the seat base (squab), seat back, or any other car componentry that it rests against, will limit the degree of combustion. Exposed body will burn the bones clean and white.

Depending on how thorough the burn is, may allow post mortem examination of internal organs, possibly lungs, to determine whether the person was alive at the start of the fire, or set alight after death. Ths is done by examination of smoke inhalation and scorching of the trachea, bronchioles and alveoli, if they survive the fire.

For me, in my role, the principal factor in a burnout is usually the collision. However, the reasons for teh collision and ignition of the vehicle are a different matter.

However, burn pattern analyses, to indicate the direction of the burn, back toward the seat(s) of the fire all help. There is a photo on my profile of a car in which a woman committed suicide, by placing a fuel can on the seat behind the driver and setting the fire. The burn pattern can be seen on the outside of the car door.

It is all a rather gruesome subject, but again fascinating from a forensic point of view. I am sure that Niamh can add a lot more to this.

Thank you for an interesting question.

Mark.