Sadly, I was reminded that the killer punch is very much a real thing when I saw news articles about a sports fan in my city who is fighting for his life after being struck. According to at least one article, he was hit just once. A quick Google search finds that one-punch deaths have occurred all over the world, including in Mobile, Alabama; New York City; Nottingham, England; and Vancouver, Canada.
So what have these one-punch killers mastered that makes them so deadly? Are they professional fighters or expert martial artists who train in iron palm or who know some secret technique? Although I can’t say for sure, I suspect that most are not. Part of the reason is that if the puncher were a professional fighter or expert martial artist, that fact would very likely come out in the media—it makes for a more interesting story, for sure. Also, from a legal standpoint it could very well change the nature/severity of the charges against the puncher. (On a side note, although it’s a myth that professional fighters and expert martial artists in the United States must register their hands as deadly weapons, it appears to be possible [although not required] to register them as such in Guam.)
How is it, then, that untrained people can kill with a single punch? Simple—it’s rarely the punch itself that is responsible for the death. Although it is possible for a single punch by itself to cause fatal injury to the brain or to induce a person to stop breathing, it’s usually when the punch causes a person to fall backwards and hit their head on a very unforgiving surface, especially pavement, that people die. Note that one-punch deaths rarely occur in combat-sport events: It’s not just that the combatants are tough and well trained. The events are also held on relatively forgiving surfaces to prevent fatal incidents.
With all due respect to martial artists skilled enough to legitimately break coconuts, bricks, boards, and other objects, that skill is unlikely to translate into a killer punch. Those objects are almost always immobilized against movement in the person’s line of force, making it difficult for the object to absorb the impact of the strike and thus making it easier (though maybe not easy) for the object to be broken. The skull and neck of a standing opponent, on the other hand, are not immobilized. And they do a remarkably good job of absorbing blows when an opponent is upright. This is especially true when the head is moved from front to back and, probably to a lesser extent, when moved from side to side.
I don’t doubt that a martial artist who can break coconuts or other hard objects could fracture the back of an opponent’s skull if the person were lying on the ground so that they couldn’t move their head. But it’s hard to get a person to lie still like that unless they’re unconscious (for example, if you’ve choked them out). In that case, though, you’ve pretty much already won the fight.
Of course there are definitely ways to help make a punch more lethal. For example, if a punch knocks the opponent out cold so that they’re unconscious on the way to the ground, the opponent can’t change their posture to better absorb the impact (e.g., tucking their chin, among other things, to prevent or at least minimize the back of their skull from contacting the hard ground and causing a traumatic brain injury). But as we can see from Western boxing matches, most fighters don’t die even when they’re out cold before they hit the canvas—mostly because they’re not hitting pavement.
So yes, the killer punch is real. And once I understood how it works, I also realized that if my opponent is at risk of hitting their head on the pavement, I would be, too—which is why I do my best to avoid getting into fights on the street.