Okay so... there's this trope of novels and film that's been the topic of discussion lately. Modern readers are getting increasingly savvy to myths of the knockout blow. I'm thinking its mostly due to the rising concern over concussions in boxing and American football, but honestly even before then, it was starting to bug me a little, too.
All of the focus on popular media is on the long term medical effects. But as a writer, I am more interested in the short term immediate effects, so I can create great scenes.
There's two aspects to the debate. One is that it isn't anywhere near as easy to knock someone out as it looks on television. The other is that if you hit a guy so hard that you cause him to lose consciousness, you could potentially kill him.
Well meaning know it alls who want to show the world how much they care about the issue of concussions are quick to glom onto the latter point especially. But they take it too far. To hear them talk, writers should stop knocking characters out entirely. It's akin to trying to kill them. Feh.
On one hand, both points are valid -- to an extent. It isn't as easy to knock a grown man unconscious as TV and movies make it look. And yes, it is potentially lethal, with a high likelihood of long terms effects without medical treatment.
On the other hand, I've seen enough MMA and boxing fights (and more recently researched the subject) to know that it's not really all that hard if you know what you are doing. As always, the truth of the matter is somewhere in the middle.
So as a writer who wants to appeal to modern audiences, you may want to check yourself before using the knockout as a plot device too frivolously. Assuming your goal is to present a believable scenario, you don't want to yank your audience out of the story.
But it's a convention of action dramas. It's one of those things that most readers will still accept, so long as you make some effort to present it realistically. So don't be too afraid to use it either. I'm a nitpicker from way back, and I'll still do it when the story calls for it.
So amid all the misinformation I've come across from people trying to sound enlightened, here's my 2 cents on the subject.
So there's a moral component. Kinda. I say kinda because typically the kind of person who would do such a thing isn't thinking in those terms. They are either dumbass criminals who just want to get away, or take someone out without making a lot of noise. Or they just want to stop the bad guy from doing whatever life threatening thing he's doing, but they are either unarmed or not capable of killing.
Still, it's something to consider. IF your character knew that that's what they were doing to their opponent, would they care? Would it cause them to hesitate? Would it cause them to go for a "less violent" approach, if they even have the time or the wherewithal to think of one.
One increasingly popular method is the chokehold. No violent striking, so no chance of a concussion. Depriving the brain of oxygen would definitely do it. But again, if the character is not trained in how to apply it properly, it either will not work... or they could kill the person in the attempt. People HAVE died from attempted chokeholds. It's why the police don't allow them to subdue suspects.
One huge gaff in this era of savvy reading audiences is to have your character remain unconscious for the remainder of any given scene, usually as a way to remove them from some key plot point.
Don't do this. Seriously.
The scientific answer to how long a victim would remain unconscious from a concussion or blood loss is: It depends. There is no hard and fast rule, and no studies have been done for obvious reasons. I can only go by anecdotal evidence from watching fights and what fighters claim.
Most get up within just a few seconds. The average seems to be more like 20-30 seconds. I've heard enough claims of up to a full minute to believe it.
But from what I can tell, if a guy is still out after sixty seconds, he is in need of serious and immediate medical treatment or he could die. There are stories of waking up hours to days later, but every one of them wakes up in a hospital room.
I could not find any reliable reports, but I am pretty sure that the odds are FAR greater of waking up within a minute of getting knocked out than of death. Have that happen to you enough times over the course of many years and you may have trouble speaking clearly or recalling your name on demand, but you'll be alive.
And fighters know this. In real world self defense, free of police regulations, it is a completely valid tactic to try to end a fight quickly by rendering your opponent unconscious. If you are unsure of your odds of winning a stand up fight, and you are in legitimate fear of your life, or driven by whatever fill-in-the-blank life or death dilemma that fuels good pulp dramas, then by all means knock the bastard out.
Well ironically, hitting someone on the back of the head is the least likely way to knock someone out. At least in the way it's normally portrayed. There's a lot of bone back there. You would have to hit a guy REALLY hard. Hard enough that you'd probably cave in their skull and kill them instead. Chances are you'll just really piss them off.
Where you want to hit is at the base of the skull, where the occipital lobe of the brain is most exposed. Trained fighters are very familiar with that spot. It does not matter how big you are. One solid hit there is lights out. The same ideas above about the length of unconsciousness and risk of long term injury still applies, thus MMA's strict rules against strikes to the back of the head. But it is the preferred method in urban self defense when possible.
The neck is another funny overused trope. The "judo chop" made famous by Captain Kirk and Austin Powers. Beyond the fact that Judo is a grappling and throwing art, hence no "chopping", it looks too silly to be believable because it is. Granted, cutting off the flow of the carotid artery is a completely valid way of rendering someone unconscious. It's been done many times. Accidentally more often than not. You've got to have fairly mad ninja skills to hit that spot with the right force at the right angle on purpose.
The neck muscles are usually too thick when striking the neck from behind or the side, too. It'd hurt like all hell, but it probably won't put them to sleep. You'd have better luck with a strike like that from the front. But that may require more focus than your average street brawler can muster.
Same with the well known "sweet spot" of the jaw. What technically happens there is similar to what I described above. The head whipsaws, but what gets actually gets hit in that scenario is a cluster of nerves below the ear which destroys your equilibrium. You never actually lose consciousness. You are messed up and wish you were pleasantly asleep, but you are aware of your surroundings beyond the deafening throb of blood in your ears. You will very likely stand up inside of ten seconds if determined enough.
Until you take one or two more shots like that.
But a well placed uppercut under the jaw... much more effective if the goal is unconsciousness.
Sidebar: It's always amazed me how infrequently the loser of a fight is described as simply unable to keep his wits about him to get up. A lot of times an opponent could legitimately lose the desire to keep fighting. They are knocked for a loop, but not out. In the famous words of Mike Tyson, everyone has a plan till they get punched in the mouth.
You can accomplish taking an opponent out long enough to escape any number of ways. Knock the wind out of them, gut punches, blows to the kidney or liver. Repeated kicks to the legs work, too, outside of a boxing ring. The ankle can only take so much. Hamstring shots are especially painful.
Another sidebar: The reason fighters often have thick necks is because they work on those muscles specifically to be able to take a punch to the head.
Of course you can always kick 'em in the junk. Again, they probably won't fall unconscious. But you won the fight.
So there you go. Just be aware that a growing portion of today's readers have grown vigilant of this particular trope.
It can still be done, but try not to overdo it. And do your best to avoid judo chops.