Let me start by saying this. Knives are lethal weapons. to attack someone with a knife ( in any way ) is using lethal force. If you would not be justified in shooting an attacker. You would not be justified in using a knife. Let me continue by saying this. Knives are not good self defense weapons. Your chances of being seriously injured or killed while defending yourself are significantly higher if you have or are using a knife ( I have seen this multiple times in my career as an EMT ) Chances are there will be some people ( teenagers included ) on here, who's first weapon that they carry was or is a knife. Using knives in a real defense situation is a catch 22 The situation where you would even [b]Begin[/b] to entertain the idea of using your knife is such a severe, dangerous and life threatening situation. In such a situation you will not even begin to be able to use your knife effectively. Your adrenalin will be so high that you will not have proper control of your arms. Regardless of how much of a tough guy or gal you think you are. You simply will not be able to use a knife effectively in a real situation. It is not hard at all to take a knife away from someone, and can be done in 2 simple movements. Any training with a knife you may have had will be completely wiped blank by your adrenalin. This is the situation where you have a very high chance of death or serious injury. Your attacker could very easily be much larger, and much stronger than you. You won't be the only one experiencing an insane adrenalin surge either, Your attacker will also. This will make them considerably stronger and potentially more aggressive than they are normally capable of. Different people handle extreme stress situations better than others. You won't know how you react to such an extreme situation until you have been in one. ( most people haven't ) Worst case scenario is that you lose most of your facilities. And your attacker does not. However this may not be the case. It is almost impossible to tell how different people will react. But since these factors would often mean life or death. Its generally not something you want to learn at the last second. If your attacker is on drugs such as PCP or Meth. They very well could be experiencing no pain or fear. I have seen people flat out SPRINTING with everything they have. With a compound ankle fracture while on PCP. Violent people on PCP are the closest thing to zombies that we have. If you are a teenager with a knife. This is a more dangerous situation. Until about the age of 21 your prefrontal cortex has not developed fully. You are physically incapable of making the executive decisions that full grown adults are capable of. And quite frankly, you should not be carrying any kind of lethal weapon. You are simply not old enough, and not mature enough. ( regardless of how mature you think you actually are ) DUH, of course teenagers will have a higher self-idea of their maturity than they actually have. And then the other side of the catch 22. If you are able to use a knife with any kind of mental and physical clarity. The situation does not warrant the use of a lethal weapon. As I said. the situation that would require you using a knife is so extreme, so volatile, and so horrifically un-fuc­king describable. That with the adrenalin you will simply not have the motor skills, and mental facilities to properly use the knife. So to the teenagers and young adults of the flood. Knives are not some kind of cool and bad-ass weapon you carry that will let you defend yourself better. It will only instill a false sense of security. And only serve to increase your chances of death or serious injury.