First-degree murder is the premeditated killing of another, according to FindLaw. Second-degree murder is not premeditated but requires malice aforethought, the intent to cause serious bodily harm and depraved indifference to life. Third-degree murder requires the intent to cause bodily harm that results from indifference, negligence or recklessness.
Although first- and second-degree murder are somewhat similar, the primary distinguishing factor is the killer's intent, notes Attorneys.com. First-degree murder cases are usually the most serious in nature and carry the most severe punishments, including the life in prison or the death penalty, in states that carry it. Second-degree murder cases are often "crimes of passion" and occur in the heat of the moment. Punishment is generally less than first-degree murder due to the lack of specific intent. Third-degree murder is the least serious of the different types of homicide and requires no intent to kill. As of 2015, it carries the least amount of punishment, typically several years in prison or a significant fine.