|MadSci Network: Biochemistry|
First, I would refer you to an answer that I gave to a related question a while back: http://www.madsci.org/posts/archives/mar97/ 853266056.Ch.r.html. However, I think I understand your question and it is somewhat different.
You are wondering if an electric current passing through the body could separate 2H2O into 2H2 + O2, and then the latter could recombine in a combustion reaction. I haven't looked anything up on this, but I would guess that there would be two big problems with this mechanism. First, from what I remember from inorganic chemistry, electrolysis (which is the name for the splitting water process or its reverse, but it doesn't matter) is very hard to do in a heterogenous solution (such as a living organism). It only works well with fairly pure water. Second, once you had the H2 and the O2, you would still have to combust them, which would need them to be mixed in high concentration (and the second they started to form they would diffuse apart, and additionally the body has specific mechanisms to neutralize free O2) and you would need the reaction to be started by heat or something, and I don't think the body itself could provide that ignition. Even if the electric current was still happening at this point, combustion needs heat, not electricity, so I don't think that would help.
I hope this answers your question. One thing to keep in mind in general with this topic is that there are about 2 million deaths per year in the US alone, and in my couple decades of life I have never heard of a single case of SHC, which would mean that out of roughly 60 million deaths there has not been a single case. It must be a very unlikely process.
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