The law generally differentiates between levels of criminal culpability based on the state of mind of the perpetrator.  This is particularly true with respect to the law of homicide.  Intentional murder requires an intent to kill, usually referred to as malice.  However, there a several mitigating factors that can reduce an intentional murder to a crime of manslaughter.

Manslaughter consists of two distinct categories: voluntary manslaughter and involuntary manslaughter.

Voluntary manslaughter occurs when the defendant has the intention to kill or cause serious harm.  However, unlike a planned murder in which there was malice aforethought, in case of voluntary manslaughter there are certain mitigating circumstances which reduce culpability.  Traditionally, the mitigating factor for voluntary manslaughter was provocation or a murder committed in “the heat of passion.”  That is, a murder committed in response to a provoking circumstance such as coming home and finding a spouse with his/her lover.  The defenses used to mitigate murder to voluntary manslaughter include:

• Provocation: The occurrence of an event which would cause a reasonable person to lose control and thereby result in the killing.
• Imperfect self-defense: This is allowed as a defense only in a limited number of jurisdictions in the United States.  Self-defense is generally a complete defense to murder.  However, in the case of an imperfect self defense, a person who acted in an honest but unreasonable belief that deadly force was necessary for self-defense could still be convicted of voluntary manslaughter or deliberate homicide committed without criminal malice.
• Diminished capacity or a mental breakdown:  This can be a defense to negate the mental state of “malice”.  The law of the United States permits a state legislature to choose a diminished mental state to justify the finding of a lesser crime.  Even though insanity is also permitted as a defense under law, this defense is different from the defense of insanity.

In case of involuntary manslaughter, there is an improper use of reasonable care or skill while performing a legal act, or while committing an act that is unlawful but not felonious.  There are two types of involuntary manslaughter statutes: criminally negligent manslaughter and unlawful act manslaughter.  In case of criminally negligent manslaughter, death of the person results due to a high degree of negligence or recklessness on the part of the accused.  Unlawful act manslaughter occurs when someone causes a death while committing or attempting to commit an unlawful act, usually a misdemeanor.