Criminal law defines offenses, establishes guilt, and determines punishments. It balances societal protection with individual rights, requiring proof beyond reasonable doubt. The government prosecutes crimes, aiming to deter, incapacitate, rehabilitate, and provide retribution. Key elements of a crime include the act (actus reus), mental state (mens rea), concurrence, and causation. Offenses range from felonies to infractions, with various types like white-collar and inchoate crimes. Criminal procedure governs investigations, trials, and sentencing, protecting defendants' rights throughout.