This lecture provides a comprehensive overview of defenses to criminal liability, categorizing them into justifications, where the act is deemed lawful, and excuses, where responsibility is negated due to factors like incapacity or coercion. It explores specific justification defenses such as self-defense and necessity, and excuse defenses including insanity and duress, detailing their legal standards and variations. The lecture also examines procedural and constitutional limitations, like due process and double jeopardy, which influence the application and availability of these defenses in the legal system. Understanding these principles is crucial for analyzing criminal cases and appreciating the balance between state power and individual rights.