There are many ways to murder someone.

Over time, Anglo-American criminal systems have come to distinguish between degrees of murder. With such a weighty crime and potentially serious punishments, the instinct to subdivide the offense according to degrees of blameworthiness seems like a reasonable way to accommodate the “proportionality principle”—the idea that crimes of different levels of blameworthiness should be treated differently. The best-known distinction between types of murder is between first- and second-degree murder.

The line between first- and second-degree murder is supposedly clear: premeditation. As the cases in this section suggest, however, defining premeditation can be difficult, and courts have taken different approaches. As you read these cases, consider also how the distinction between first- and second-degree murder serves the goals of criminal punishment. Which is more blameworthy, and thus more deserving of punishment as a matter of retribution? Who is more dangerous, and should be incapacitated longer, or permanently? Who can be deterred—and who can’t?

Distinctions within the group of crimes known as “homicide” depend on more than the different mens rea levels associated with a killing. Knowing that a person killed someone (act) with purpose or knowledge (mens rea) does not necessarily mean that the person committed “murder.” Criminal law sometimes takes additional circumstances into account when assigning blame.

In the case of knowingly or purposefully killing someone, provocation or extreme emotional disturbance might mitigate the crime of murder down to voluntary manslaughter. As the cases below demonstrate, different courts have taken different approaches in defining whether and what circumstances might lessen the seriousness of an intentional killing.

As you read these cases, consider the challenges that courts face when they downgrade a crime committed with the same basic act, result, and mens rea. Where and how do courts draw lines between which circumstances mitigate murder, and which circumstances don’t? In determining the effect of provocation or emotional distress, should courts look at a criminal’s individual nature, or hold him/her to an objective standard?