Well, having done a bit of research on it I can say a few things.
There seems to be two types of cases, Documented and undocumented (friend of a friend type).
The documented cases are not that mysterious anymore, since significant testing recently has shown how the body burns. The victim(usually elderly) passes out somehow, Drunk, carbon-monoxide, etc... an ember or cigarette starts their clothes(or blanket, etc...) smouldering. What happens next is important, the persons own fat has to 'wick' through to the cloth fibers, this causes the entire area to turn into an inverted candle, allowing for incredible heat to be generated, but all locally. Experiments with (dead) pigs in clothes have shown every trait of 'spontaneous combustion', the exessive heat allowing for full skeleton burn, while leaving the unclothed area untouched, and leaving surrounding objects usually unharmed.
in almost all known cases of spontaneous combustion, the situation above can completely explain what happend (even for partial burns, where the victim remains alive, and only loses an arm, or fingers before being discoverd. There are one or two cases where it doesn't quite match, but there are 'extenuating circumstances' One modern case, the person who discovered the body says she was only gone 15 minutes, which is not enough for the full torso burn in that case, but she could have fallen asleep on the couch as it was late at night and by her own admittance very tired, as she was watching tv (she cannot remember what was on)
The undocumented cases fall in the category of 'a friend of a friend saw this guy just burst into flames at a party'. Which honestly can hardly be believed.
As for the case above, he could very well have been wearing a hat.
RX
