Self-Defense by use of physical force is allowed when a person reasonably believes that the use of force is necessary to protect themselves or others from the imminent use of force by someone else. In order for self-defense to be successful, the defendant will need to establish that they believed the use of force was necessary to protect themselves or others from physical danger AND that a reasonable person in the defendants position would have acted in a similar way. The rationale behind this defense is that someone does not have to wait until they are attacked or injured before they can fight back. You cannot be the initial person causing the violent act to claim self-defense. A defendant does not need to prove that they were justified in using self-defense. The prosecution is required to prove beyond a reasonable doubt that the defendant was not justified in using self-defense.