Self-defense is the right of every living thing to defend itself from attack. You may use every means reasonably necessary to stop an attack against yourself or someone else. Being reasonable means that what you use to stop the attack should be commensurate with the type of attack. For example, you may not legally shoot someone who slapped you but you may legally shoot someone who attacks you with a knife.
Mental aspects. The state of minds of the predator and the victim.
Physical aspects. Your body reacts to the moment.
Legal aspects. It's something that must always be considered.
Criminal behavior. Why they do what they do.
Techniques. How to defend yourself.