A more thorough explanation:

The urban-psychosis defense, also known as the urban-survival syndrome, is a self-defense theory that can be used by a defendant who uses unreasonable force. This defense argues that the defendant may be acquitted if they live in a dangerous environment that heightens their fears of injury to life or limb to the point where the force used seemed reasonable and necessary to the defendant.

For example, imagine a person who lives in a high-crime area and is approached by someone who they believe is going to harm them. If the person uses force to defend themselves, they may be able to use the urban-psychosis defense in court if they can prove that their fear of harm was so great that the force used was reasonable.

Another example could be a person who has experienced trauma in their past, such as being a victim of a violent crime. This trauma may cause them to have heightened fears and reactions in dangerous situations, which could lead them to use force in self-defense. In this case, the urban-psychosis defense could be used to argue that the force used was reasonable given the defendant's past experiences.