Most reported cases have not been supported by thorough investigation, but have relied heavily on hearsay and oral testimony.
There have been many theories advanced to account for SHC. These generally fall into one of three groups: the paranormal (ghosts or dark spirits caused it); explanations that credit some previously unknown and undocumented biochemical phenomena, such as the spontaneous ignition of natural human gases, perhaps in the presence of high blood alcohol concentration; and natural explanations such as the dropping of a lit cigarette.
None of these explain, however (except perhaps the supernatural), why in some cases, it has been reported that the body of the victim has been burned beyond recognition, while the surrounding materials, such as bedding, chairs, etc. have been left unscathed.
Scientific understanding suggests that in cases of reported spontaneous combustion, there has always been a legitimate source of ignition, such as a burning cigarette, candle, or lantern flame.
Many unverified causes have been suggested, such as the fact that since every body contains flammable gases, mainly methane in the intestines, an electrical charge could ignite these gases, possibly caused by the friction, such as might caused by creating a spark while walking across a carpet.
Further suggestions have included: lonely people may fall into a trance state immediately preceding their spontaneous combustion. The idea is that emotionally disturbed people can set off a chain reaction of nitrogen combined with mitochondrial “explosions” within the body. Nitrogen, however, is an inert, non-flammable gas.
Also, that drinking can raise the blood-alcohol level to such a point wherein the body might spontaneously ignite. However, ethanol typically only burns if the concentration is higher than 23%, whereas a fatally toxic level for a human being is about 1%, and it requires an ignition source.
Finally, the controversial phenomenon of “ball lightning” has been suggested as a cause of spontaneous human combustion.
Realistically, it is more likely, since reported victims have usually been alone, that something like a heart attack or stroke has caused sudden death, resulting in the dropping of a lit cigarette or contact with a candle. The “wick effect” hypothesis suggests that a small external flame source can char the clothing of the victim at the point of contact, splitting the skin, which then leads to the releasing of subcutaneous fat, which is absorbed into the burning clothing, causing it to act as a wick. Experiments have been performed with animal tissue (don’t ask me to imagine or describe them!) that have proven that such a phenomenon is possible.
However, none of these proposed explanations account for the fact that often, the surrounding materials have not burned. I want to emphasize this, as it has been reported in numerous cases. I wish my biochemistry professor father was still alive to consult…
Do we believe in magic or in SHC? You must decide for yourself!