Murder is the act of killing a human being with malice aforethought. Malice aforethought is a legal term meaning the perpetrator has an evil mind at the time of the crime. It used to require premeditation, but today the law does not require an appreciable amount of time to pass between the formation and execution of the intent to kill.
Criminals and sociopaths are responsible for many murders, but the vast majority of homicides involve people who are not particularly dangerous or unusual other than the way they ended their lives. Men commit over 80 percent of reported murders, but the reason for this is more than a biological tendency.
There are a number of different categories of murder, including first-degree murder (premeditated), second-degree murder (spontaneous or without planning), and felony murder (death caused during the commission of a felony). Some states have additional distinctions for other types of killings, such as murders committed by police officers in the line of duty or cases of justifiable homicide.
Criminal law differs in different countries, but most common-law systems define murder as a serious offense with stiff penalties. The crimes of manslaughter and culpable homicide are less serious, with the former involving reckless killing and the latter involving killing without intent or as the result of a violent emotional outburst. A jury may sympathize with a murder defendant and choose to reduce the charge to manslaughter. However, the jury must still find that the defendant intended to kill the victim or intended to cause serious bodily harm.