"It is important to understand that "can cause" won't cut it, nor will the "possibility".
Now is a good time to review the legal definition of deadly force."
it's a very good suggestion to go back and review the legal definitions. And in fact I think I will do that this weekend.
But to be practical - these Knockout Attacks involve a small hostile group of people. Several people grab the victim, while another one punches him/her in the face. In the moments that these people are in close proximity, I have got no idea of their "commitment to fight peacefully" - whatever that means. I have to assume they may be carrying a blade or a gun. And in fact one of those news stories did show that the guy delivering the knockout punch had a pistol on his body. Therefore, I do not have a problem with the application of a high level of force in these types of assaults. While the results may be "tragic" if some teenagers are wounded or killed, that fact is that they are putting their lives at risk if they attack people in this way. Doing stupid things can get you killed.
In reality, I would probably make a judgment call about the teenagers, how many there were, and what kind of physical threat they posed. I've got good martial arts training, and I don't have a problem with using it. But if the teenagers are big and aggressive, they could get shot doing this. Of course, it's all hypothetical because the laws on California where I live do not allow me to carry a loaded firearm in public anyway - Hahahahaha!!
CA R