Ummm… no. Manslaughter is what’s called a predicate-based offence, i.e. if you commit an offence (say assault) which creates an objective risk of bodily harm and the victim dies as a result of that offence, then you are guilty of manslaughter. Consent, of course, negates assault so if there is no assault (i.e. no predicate offence), there is no manslaughter, just a dreadful accident (unless you wanted to go the criminal negligence route).

In any case, the common law has long distinguished between activities with social utility (medicine, sport) and those without (sadomasochism, fistfighting). See the Jobidon decision, in which the court held that a man could not consent to a parking lot brawl in which serious bodily harm resulted, partly because the wider society has no interest in seeing “cults of violence and sadism” spring up across the land: http://en.wikipedia.org/wiki/R._v._Jobidon

For someone who opines so piously about the law, you are awfully ignorant of it, aren’t you?

I could try to tease out distinctions for mutual competition and beneficial purpose in the other examples you described, but I don’t think that’s the real question.

Is this a matter of line-drawing or principle? In other words, is that this particular behavior isn’t so far out and, so long as everyone was okay with it, we therefore shouldn’t meddle? Or is it that, given mutual consent, there’s no conduct at all short of taking a life that should be outlawed as too risky and reckless with human life?

What if they get off from playing a modified form of russian roulette, putting the gun to other person’s head? Is it better to stop them, or to bury one and charge the other with manslaughter?

Uh, no. If you choke and kill your wife, you’d better hope your kink included having lots of witnesses with video cameras, because the default presumption should obviously be that someone who chokes another person to death has committed a crime. Hell, even if there’s ironclad proof that there was consent to the choking, we’re still at least talking manslaughter. (Presumably if you kill your opponent in the boxing ring, barring extraordinary circumstances, you’re also in legal trouble.) But when you’ve got the putative victim here saying the whole thing was consensual, it seems to me that it ought to make a difference. For any risky behavior you permit, you can imagine a case where someone commits murder and claims it was part of a consensual activity; I don’t think that constitutes a case against ever permitting risky behavior.

The ruling is clearly bad and overbroad as a point of law. But is the answer that people are free to willy-nilly choke out their wives and claim they had consent should the tragic but predictable occasionally happen? That seems overly permissive. Are the concerns of asphyxiation enthusiasts so sacrosanct? I gotta think there’s a middle ground here.