Self-defense and the defense of one's own property are among the defenses to criminal liability.
Describe these defenses and the level of force permitted in exercising them.

We all have the right to protect ourselves from physical attacks by others; this is the right of self- defense. In most states, the force we use to protect ourselves must be reasonable under the circumstances, though. The force used must be justified by the degree of threat posed in a given situation. If someone is about to take your life, the use of deadly force (shooting that person with a gun, for example) might be deemed reasonable. If, however, someone in a shopping mall tries to pick your pocket to steal your wallet, you normally do not have a right to shoot the thief, because there was no physical threat to your person.
We also have the right to use reasonable force in the defense of property. In particular, if someone is trespassing on our property or is stealing our property, we have the right to use force to stop the trespassing or prevent the theft; again, the amount of force used must be reasonable. Because human life has a higher value than property, deadly force is normally not allowed in the protection of property unless the thief or trespasser poses a threat to human life.
Depending on the situation, the castle doctrine may come into play. This doctrine is based on the common law concept that you have a right to defend your home (your castle), yourself, your property, or an innocent person from the illegal acts of another. In general, if an intruder is in a home, the legal residents of the home do not have a duty to retreat.
Rather, they have an express right to stand their ground. About half the states have expressed this principle in legislation, but the details of how the principle is applied vary significantly across the states.