By: Dan B.
The short answer to that question above is: No, knives are not good self-defense weapons. Now, let me explain, by exploring the defensive capabilities of this weapon.
First of all, a knife is unable to effectively block a strike from any other weapon by actually stopping the weapon itself. The only means one has to stop an incoming blow with a knife is to slash the attacker's arm/wrist as he is swinging his weapon at you. This means you must be at least partially within the effective striking range of the attacker's weapon in order to stop it, and if you don't stop his attack with your slash, you're probably going to be hit. This is why most (good) knife instructors will tell you to use your free hand (the hand not holding your knife) as a supplemental defense to block at the same time you are countering an attack with your knife. In fact, even if you successfully slash the arm of the attacker as he is swinging at you, that is no guarantee you will stop his attack. Even though knife slashes are impact cuts, you get more cut than impact. Your knife will slice across his arm, but may not halt the momentum of his blow. Thus, when you are attacked, a knife allows you to strike back at the opponent; it does not necessarily give you the ability to stop an in incoming blow.
In light of this, if you are using a knife for defense, your stance is very important. Without going into detail, typically you want to keep your knife between you and your attacker, and you want to keep yourself as compact as possible. I always think of a snake, coiled and ready to strike. Because that's what you do with a knife - you strike at whatever comes into your range. Stances that put the knife hand to the rear are mostly useless, except in cases where you are being attacked with a long impact weapon and you want to block and trap it with your free hand, or in cases where you think your attacker might charge you. Just FYI - charging a trained knife fighter is basically committing suicide.
I've examined the knives questionable ability to stop an incoming blow, now let's look at a knives ability to stop the attacker himself. The truth is that a knife wound that can be fatal later may not even be felt during the heat of combat. Now, if you are able to completely sever a tendon or major muscle group, you will incapacitate the attacker. However, if you are relying on pain and blood loss to stop him, although it will eventually, it may not have any immediate effect. The bad guy may continue to beat on you, even after you've stabbed him a couple of times.
Now, don't take any of this to mean that a knife isn't a good weapon. I've never said that. A knife is an excellent offensive weapon. It is easy to carry. It must only touch your opponent to do harm. It is just as effective in grappling range as it is at the furthest extent of its reach. It can literally move quicker than the eye can follow and it can be maneuvered in ways that it is momentarily concealed from the opponent during combat, even if he already knows you have a knife. When it comes to lethal force, a knife is arguable the close-quarters king.
When I talk about self-defense though, I am talking about my desire to stop an attacker, and prevent harm to myself. This may or may not involve harming my attacker. If I can yell for help and attract attention, or get into my car and lock my door before an attacker can get to me, I have successfully defended myself. And that is my beef with the knife as a defensive weapon. Using a knife, I will certainly harm my attacker, but I may or may not stop his attack and prevent him from harming me. For self-defense, I am more concerned about defending myself, than I am about hurting the other guy. The difference between the two can be subtle, but it is present. Using a knife is a great way to hurt the other guy, but it is not necessarily a great way to stop him from hurting me. And of course, a knife is considered a lethal force weapon and so it should only be used in situations where that is justified, thus limiting it's utility as an overall defensive first response weapon.
So what sort of weapon do I prefer for self-defense? Aside from pepper spray, I prefer an impact weapon such as the ASP baton. It can actually stop an incoming blow. You can stay beyond the reach of most other close-combat weapons except maybe a pipe or baseball bat. And I don't care how tough you are - or how drugged you are - if I break your knee you won't be running after me, it's just not physically possible; the same is not necessarily true for a knife wound. Also, with an impact weapon there's less chance you'll have the guy's blood all over you. And these days, with blood-born pathogens, that can be pretty important. Finally, with proper use the ASP baton is considered a less-than-lethal weapon, which (via strikes to the head) you can escalate to probable lethal force if necessary. Thus, in my opinion, an impact weapon is applicable over a wider range of defensive scenarios than the knife. Of course, a knife isn't always lethal either, but a knife is more likely to be lethal than a baton, in that there are a greater number of potentially lethal targets for the knife than there are for the baton. With a knife, it is quite possible to kill someone even if you are skilled and trying not to kill. I would rather not have that legal and moral liability, especially when a baton is more effective at stopping an attack and preventing harm than a knife is anyway.