Criminal Law

Criminal law in the Anglo-American tradition has evolved significantly over time, particularly in the last two hundred years, as statutory law has continued to redefine crimes and their punishments, and as our understanding of crime and criminality has changed. These developments have been influenced by larger currents of social philosophy and changing views within society itself. Rules considered in the classic cases selected below include the insanity defense and its origins and influence, the standard for self-defense in homicide cases - as articulated in a fascinating English case of cannibalism - and the definition of malice as a standard of mens rea.

M'Naghten Rule (1843)
Also known as the “right-wrong” test, the M’Naghten Rule is a legal standard used to determine whether a defendant can be excused from criminal liability by reason of insanity. 

Defendants are presumed to be sane and have a sufficient degree of reason to be responsible for their crimes. To rebut this presumption one of the following is required:

To establish a defence on the ground of insanity, it must be clearly proved that at the time of committing the act the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing, or as not to know that what he was doing was wrong. ^[1]

The M’Naghten Rule remains the most common insanity standard across U.S. state jurisdictions as of the time of this writing. ^[2]

Regina v. Dudley & Stephens (1884)
Regina v. Dudley & Stephens stands for the rule that homicide is not justified by necessity unless it is committed in self-defense.

People v. Beardsley (1907)
Criminal liability for failure to act can only be imposed if a legal duty of care between the parties exists. A legal duty of care can arise from statute, contract, or certain kinds of relationships, such as parent-child or spouse-spouse. Although there may be a moral duty to assist, that alone is not sufficient to establish a legal duty of care. 

Regina v. Cunningham (1957)
Regina v. Cunningham clarified that the term “malice,” the most demanding standard of mens rea, means that the perpetrator either had the actual intention to cause the resulting harm or that they recklessly disregarded the foreseeable risk of the specific resulting harm. Malice is more akin to recklessness, rather than ill will.