In action movies, whenever the hero and his posse are trying to infiltrate the bad guys’ lair, they’ll often try to get rid of various guards and henchmen by performing silent kills. The cliched way to do this is to sneak up on the bad guy and snap his neck. It is shown that the neck snap is instantly incapacitating. But is the neck snap lethal in itself, or does it result in below-the-neck paralysis that eventually leads to suffocation, as the diaphragm is no longer receiving impulses from the brain?
The “Lethal Neck Snap” is a modern fictional convention akin to the “Knockout Karate Chop to the Base of the Neck” that was in vogue in the '60s and '70s.
A broken neck is potentially quite dangerous, for the reason you give, but not necessarily instantaneous, and certainly not able to be inflicted reliably in the fashion it’s usually shown. A windpipe-crushing choke hold is probably the real world equivalent for unarmed stealthy lethal attack, though it’s much slower in its effects, and the victim has more opportunity to struggle. Real Special Ops forces are more likely to use knives, garrotes, or silenced firearms for the purpose.
If your neck in broken around the level of C2 or C1 in laymens terms it will damage the area that controls your breathing and heart rate. What happens is you stop breathing immediately and die shortly after.
On a real world note I treated a man with a broken neck from a car accident at the level C6. He was incapacitated and his breathing was severely compromised. His skin color was ashen (bad) and his belly looked like a giant blob moving awkwardly with little chest movement. If left alone how he was he probably would of died with in twenty minutes from respiratory failure. He could no longer breathe effectively on his own.
So to answer your question yes a neck snap is lethal and the area around C2 potentially will cause “instant” death pretty much.
Whoops, too early in the morning.
I didn’t really answer what you were looking for. The movie based move would probably not be reliable as pointed out. However, I would never take the chance to actually find out 
Car crashes the most frequent cause of this type of death inflicts an extreme amount of force in the area that will cause “instant / rapid death”.
The chokehold is incredible I have actually been victim to this once and I was unconscious in about 8 seconds. My only reaction was to grab the arms around my neck which did not work. I woke up in a state of complete panic. Last time I’ll ever volunteer for something “cool” at a party standing next to MMA fighter.
Good luck snapping someone’s c2 or c1 with your hands. Especially with Hollywood technique, where they just sort of grab them by the chin and yank backward.
It’s important to point out you almost certainly weren’t “choked” into unconsciousness in 8 seconds. What probably happened was there was enough pressure on the major arteries leading to the brain that it interrupted blood flow. I’m not sure I’ve seen anything like that in Hollywood.
I’m well aware of what happened. Sadly the “pressure on the arteries which causes a lack of oxygenated blood to reach the brain causing a rapid loss of mentation followed by unconsciousness hold” never caught on.
I always saw the grab and turn past the shoulders to one side. This is probably beyond the normal person’s reach in terms of strength though. Those capable of doing it probably wouldn’t be too stealthy either.
Yeah, I’m more interested in the grab where you grab the guy’s head and turn it one way (left/right) and then turn the body/shoulders the other way - basically try to twist the head around 180 degrees. Would this actually kill a guy, and is within the realm of human strength?
It would break his neck and render him unconscious and incapacitated. Whether it kills him depends on exactly where the break occurs.
Theoretically, yes. On a real, struggling human being, you’d have to be very strong and very lucky. And if you’re that strong, punching the person on the back of the head would be more certain.
I would bet this is on border of “possible”. If a person were very, very strong, the other person had a particularly weak or congenitally compromised spine, and the attack was totally unexpected so that the breakee had no chance to tense the muscles of the neck, maybe. But routinely? I don’t think so.
If you do happen across someone who could bring it off, I would make some effort to remain in his good graces.
If I wanted to incapacitate someone instantly from behind, I would do the sleeper hold found in judo and ju-jitsu, choke the fellow out, and then kill him with a strike to the trachea once he was unconscious.
Regards,
Shodan
I assume Mythbusters hasn’t tackled this one yet.
Adam: Uh-oh! That’ll never make it to television…
Note to self: Never, ever shoplift from the Museum of Modern Art’s gift shop.
Is’nt this the aim of a long drop hanging?
Anyone else hear this in the voice of Dwight Shrute?
And if you’re going to try this on someone, just use a knife. I mean, if you want to kill someone quickly, have the drop on them, and for whatever reason don’t want to use a gun, the knife is much better instrument than any hand-to-hand technique.
Another thread on the subject:
I’m glad this is not one of those ‘need answer fast’ questions 
I hear the thing to do is to cover their mouth and stab into the side of the neck and tear out through the trachea and major arteries. Instant unconsciousness results followed by quick death. Never tried it myself.
I can say that after butchering a few animals, it is amazing how tough some of that connective tissue is.