A killer is a criminal who takes the life of a human being or an animal and who is driven by unlawful and personal motives.
There are many grounds for killing someone that are considered as still being in the scope of legality: a person who kills for self-defense motives or for the defense of a nation in war-time is not considered as a killer. Killing an enemy in the battlefield could make you a hero, same thing if you killed an intruder who threatened the life of your family. In both cases, you killed for legitimate purposes and in the name of each and all have the right to defend.

Some psychoanalysts dedicated their study on the Killers' typical behaviors in order to provide informations on the various profiles of such people. The result of their studies indicates that killers are not an homogeneous group of uniform personalities.

Some people for instance became killers because they couldn't overcome their feelings in a moment of climatic rage. The typical example is the jealous husband who kills his wife because he caught her in bed with the neighbor. In this case, the act of killing wasn't premeditated. Some mentally ill people became killers for reasons that remain quite unknown to a healthy mind, while some others killed in cold blood after having meticulously planned their act for revenge motives, for a financial compensation or for ideological purposes.

Killing is a process in which someone denies the basic right of an other person. In our society, the law makes provision for killers to be severely punished. Furthermore, the collectivity has the moral duty to make citizens capable of empathy and guilt. When we look at serial killers, it seems that our society is far from being flawless.