A more thorough explanation:

Criminal intent, also known as mens rea, is the mental state required to convict someone of a crime. It is one of the fundamental aspects of criminal law, along with the criminal act, or actus reus. The specific intent required to sustain a conviction varies from crime to crime and from state to state.

In some states, criminal intent is split into four categories:

• Acting purposely: The defendant's goal was to cause the criminal conduct.
• Acting knowingly: The defendant was practically certain that the conduct would cause a particular result.
• Acting recklessly: The defendant consciously disregarded a substantial and unjustified risk that the criminal conduct would occur.
• Acting negligently: The defendant was not aware of the risk criminal conduct would occur but should have been aware of the risk.

Each crime will have an associated level of criminal intent necessary to sustain the conviction. For example, standard murder typically requires a party to purposefully or knowingly cause the death of another human. Therefore, a party who only negligently causes the death of another human cannot be found guilty of murder because the criminal intent was lacking.

Penalties for the same conduct increase the higher you travel up the mental state/specific intent list. For example, manslaughter, which requires recklessly or negligently killing another human, is punished less harshly than murder. Additionally, a higher mental state can substitute for a lower one. A party who purposefully kills another human can still be found guilty of manslaughter even though their criminal intent was purposeful rather than reckless.

A minority of states instead choose to follow common law doctrines of malice. These jurisdictions determine liability by categorizing the type of malice accompanying any given criminal action between:

• Express malice: Deliberate intent to bring harm to the victim.
• Implied malice: Indifference to harm that a victim may suffer due to the defendant's carelessness or inattentiveness.

For example, if someone intentionally shoots and kills another person, they have acted with express malice. If someone accidentally hits and kills a pedestrian while driving under the influence of drugs or alcohol, they have acted with implied malice.

These examples illustrate how criminal intent is an essential element of criminal law. Without the proper mental state, a person cannot be convicted of a crime, even if their actions caused harm or damage.