Mental states that determine the degree of guilt or culpability in criminal law are generally classified from highest (most worthy of blame or punishment) to lowest as: (1) intentional; (2) knowing; (3) reckless; and (4) criminal negligence.

A person acts with criminal negligence, or is criminally negligent, with respect to circumstances surrounding his conduct or the result of his conduct when he ought to be aware of a substantial and unjustifiable risk that the circumstances exist or the result will occur. The risk must be of such a nature and degree that the failure to perceive it constitutes a gross deviation from the standard of care that an ordinary person would exercise under all of the circumstances, as viewed from the accused person’s standpoint at the time of the alleged criminal negligence.

Criminal offenses or crimes often specify the culpable mental state the prosecution is required to prove to convict a defendant of the offense. These culpable mental states are generally defined in the relevant state or federal statutes—usually in the penal or criminal code.

In California, the mental states that determine the degree of guilt or culpability in criminal law are indeed classified into different levels such as intentional, knowing, reckless, and criminal negligence. These mental states are critical in establishing the requisite mens rea, or 'guilty mind,' for a criminal offense. Intentional actions are those done with the purpose of causing a particular result, while knowing actions are those done with awareness that the result is practically certain. Reckless behavior involves conscious disregard of a substantial and unjustifiable risk, and criminal negligence refers to a situation where an individual fails to be aware of such a risk, and this failure is a gross deviation from the standard of care an ordinary person would exercise. In California, these definitions and applications are codified in the California Penal Code. The prosecution must prove the defendant had the specific mental state required by the statute for the crime charged in order to secure a conviction. Each crime specifies the mental state that must be proven, and the absence of the requisite mental state can be a defense against the crime charged.