“I’m going to disagree with you because everything you just mentioned had an escape clause built into it. They weren’t really risking anything.”
Well, we can offer dozens of other examples, because humans override these instincts everyday. Flying on planes, riding a bicycle, driving an automobile, going to war, drinking alcohol, taking drugs, fasting, standing on a high balcony, playing with fire, etc, etc. All of them involve overriding our survival instincts, and not all of them are without consequence.
In fact, it’s such a common thing that parents teach their children how to do it, and when someone has trouble overriding those instincts in some circumstance, rather than call them “normal”, we say they have a “phobia” and call them “abnormal”. This is accurate as far as humans go, because being able to override these instincts on a whim is actually normal human behavior.
“We had a drowning in the bathtub murder trial around here not too long ago, and the prosecutor’s point was that even when unconscious a body’s reaction would be to flail out of that water.”
The prosecutor was slightly mistaken. There is an instinct, not a reflex, to flail your arms when you are near drowning, in order to push your head above water enough to take a breath. However, instincts don’t matter when you are unconscious, only reflexes can act at that point, because instincts are part of the higher nervous system, while reflexes are not. Once a person is unconscious, there is no opportunity for an instinct to do anything.
Besides, even if what you mentioned was a reflex, reflexes are specific to the stimuli which cause them. You can’t assume, because a reflex exists in response to one stimuli, that there would be a similar reflex in response to completely different stimuli. So, the human response to drowning has little to do with the human response to asphyxiation, since the stimuli are different.
Here are the observed human responses to asphyxiation:
* rapid loss of consciousness (at 8-18 seconds),
* convulsions (at 10-19 seconds),
* decerebrate and decorticate rigidity,
* loss of muscle tone (between 1 min 38 seconds and 2 mins 15 seconds),
* isolated body movements ‘from time to time’ (last between 1 min 2 seconds and 7 mins 31 seconds),
* deep rhythmic abdominal respiratory movements (last between 1 min 2 seconds and 2 mins 5 seconds).
http://www.forensicmed.co.uk/pathology/pressure-to-the-neck/
None of those actions seem deliberate enough to save you if your body weight is working against you. Perhaps a convulsion could dislodge you by random chance, but that would be unpredictable.
The prosecutor won.
Again, all of your examples are of tested behaviors that have such a high correlation with safe indulgence that there is no sense of gesturing to kill oneself.
People would think me a nut if I said, “If you don’t give me love, then I’ll fly on an airplane.”
But, if I saw a bit on my wrists or wrap a belt around my throat, then those are known suicidal methods. One can reasonable use them to telegraph despair without necessarily meaning to kill oneself. The danger of a gesture is that one accidentally be successful.
So, I repeat. Slumping down with a belt around one’s neck requires great determination to follow through with an actual asphyxiation. It’s contrary to self-preservation and good sense.
So, it is UNUSUAL. It is easy to imagine a gesture gone bad OR a great determination to kill oneself. The sawed on wrist with a dull blade suggests a real possibility of a gesture gone bad. The ability to stand suggests a gesture gone bad.
So, if they end up telling the family this might have been a gesture gone bad, then I won’t be the least bit surprised.