ABSTRACT
This chapter explains two doctrines that mitigate intentional killing from murder to manslaughter arise from the actor having some abnormal mental state, either transient or long term. It reviews the existence and several variations of mitigations under current US law, how they came to their present form, and rationales one can offer in support of such mitigations. The Model Penal Code's mitigation doctrine has also altered the allocation of the burden of persuasion between the prosecution and the defendant. Another challenge to allowing mental illness to negate culpability focused on the nature of culpability. Many of the codification proposals in these jurisdictions proposed adopting the Model Penal Code 'extreme emotional disturbance' formulation of the mitigation. Indeed, if the higher grade offence, such as murder, carries a mandatory death sentence, then grading decision is all-important. The extent of their importance depends upon the nature of a jurisdiction's sentencing system and the practical effects that follow from the determination of offence grade.
