If reasonable force us used against an Individual and there is a threat of imminent odily harm or death, and the individual defends themselves, that person may be acquitted of first-degree murder. To argue perfect self-defense, and have it result in a full acquittal the threat must be grave and the force used In response must be reasonable. With an argument of imperfect self-defense it will not result in a complete acqulttal, out most 11Kely a lesser cnarge sucn as manslaugnter.
In tne case of imperfect self-defense, the offender uses more force than is necessary to diffuse the threat such as if the force was necessary to defend themselves but using lethal force was not necessary. When a person pleads not guilty by reason of insanity, the defense is arguing that the defendant has a mental defect that makes them incapable of forming the intent that is required to prove first-degree premeditated murder.
Each state has different standards when it comes to establishing an insanity defense, and they examine whether or not the defendant understands that nature of their conduct at the time the offense was committed. The last is provocation which is not commonly used as a complete defense but can also reduce a first-degree murder charge down to a manslaughter conviction. Provocation uses the argument that the defendant was provoked and lost control and acted in the heat of the moment which undermines proof of intent.