When can a defendant plead self defense?

A defendant can plead self-defense when they believe they are in imminent danger of harm and use reasonable force to protect themselves. The force used must be proportional to the threat faced, meaning lethal force can only be justified if the defendant believes their life is in immediate danger. Additionally, the defendant must not have provoked the encounter or have had a safe opportunity to retreat, depending on the jurisdiction's laws. Ultimately, the specifics of each case will determine the viability of a self-defense claim.