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 Illinois, the mental state of an individual at the time of committing a crime is crucial in determining their degree of guilt or culpability. The mental states are ranked from most to least blameworthy as follows: intentional, knowing, reckless, and criminal negligence. Intentional actions are those committed with the purpose of causing a particular result. Knowing actions are those where the individual is aware that their conduct is practically certain to cause a result. Reckless behavior involves conscious disregard of a substantial and unjustifiable risk. Criminal negligence occurs when an individual fails to be aware of a substantial and unjustifiable risk, where such failure is a gross deviation from the standard of care an ordinary person would exercise. In Illinois, these mental states are defined within the Illinois Compiled Statutes, particularly in the Criminal Code. For a conviction, the prosecution must prove the defendant acted with the requisite mental state as specified by the statute for the particular offense.