Movies make it seem like you can just walk up to anyone and twist their head slightly and break their neck, based on the lack of any murder case I can remember involving this method of execution I’m thinking it is bullshit but am open to being amazed.
…and they’ll just invariably drop like a sack of potatoes, never screaming or anything. You’d actually have to do damage to the spinal cord itself, wouldn’t you?
Need answer fast?
I was thinking of asking this too.
I think there have been lots of previous threads, none of which give a satisfactory answer.
What is the amount of force calculated to snap the neck in a long drop performed using the British tables? That might give a rough guide to whether it is possible to do manually, no?
IIRC the issue is not breaking the neck, that’s pretty easy with practice. The problem is breaking it in a place that will kill the person and not just paralyze them.
Paralysis would be below the neck though wouldn’t it?
That would effectively remove their ability to act, make a noise or even breathe, so effectively killing them…albeit not instantaneously.
American Kenpo teaches techniques for doing this but it’s kind of hard to practice. You only get to use the white belts once. 
If you do it right I think you could get enough leverage to break a neck, probably. Maybe someone who has broken a lot of necks might be able to pull it off but even then I doubt the victims would just drop over dead like in the movies. In fact, I’m going to go out on a limb here and claim that a lot of the gun and fighting action in movies in not well researched.
I had a friend in the Marines who claimed he was taught a way to come up behind someone and kill them by breaking their neck. It did not involve the movie style grab and twist, but holding the other person head in such a way that when you knocked them down you would fall on them with all of your weight and that would break the neck. No way of knowing if he was telling the truth or if he was telling the truth wheter it would have worked.
In the NHL, Todd Bertuzzi took a cheap shot similar to what you describe on Steve Moore and broke three vertebrae in Moore’s neck.
It’s entirely possible, though difficult. Twisting the neck rapidly will cause unconsciousness. This is what happens when boxers hit someone on the point of the chin. Their neck is rapidly twisted compressing the nerves in the spine causing unconciousness. The neck can be broken this way also. That’s why football has a serious penalty for face-masking. Grabbing the face mask of a running player can break their neck. Death is harder. The trauma has to be sufficient to damage the brain stem or cause some other vital function failure. But when the guy is unconcious and paralyzed you can just stick a knife in him to finish.
I forget where the autonomic nerves tie in. Between C3 and C4 maybe. Avove that point it is death and below the heart still beats and the person still breaths.
Was Steven Seagal famous for overusing this move in his movies? I remember a Will Sasso spoof of him doing a lot of neck-breaking:
You must mean this thread. 
Does it really matter if you killed a guard or just dropped him? That’s usually when movie infiltrators do the whole “neck twist” thing - the big boss gets a lot more time to talk and run through factories and such.
That OP wins TSD!
Next you’ll be telling us that the Vulcan Nerve Pinchis fake. 
I have to imagine that a Mr. Universe type could do this to a 10 year old child. Now we just need to have a movie that justifies that situation. 
For what it’s worth, I was taught in Army basic training to break necks by approaching an enemy from behind, grabbing their right shoulder with your left hand, the left side of their chin with your right hand, and pulling your hands apart quickly.
Obviously, I never tried it, and I always figured you’d be pretty lucky to get into that position unless you sneak up on somebody, but I can’t see why it wouldn’t work if you used enough force. Grabbing the shoulder and chin like that gives you a lot of leverage.
A quick, hard squeeze or strike of the carotid sinus from behind would require less force and probably be more predictably effective on an unaware opponent.