Murder, also known as homicide, is the activity of one human being purposefully taking the life of another human being, without lawful justification. It is known to be a sin from the Biblical times and is a crime in America and most countries. It is commonly considered one of the most serious crimes one can commit.
Premeditated murder, known in law as "murder in the first degree" is considered the most serious forms of murder, followed by murder in the second degree.
In most legal jurisdictions, manslaughter is a form of a form of lesser homicide, separate from murder. Involuntary manslaughter occurs when a person unintentionally ends another person's life through their unlawful incompetence. Voluntary manslaughter is a form of Killing in which the perpetrator acted under circumstances in which any "ordinary person" would become mentally disturbed, so much so that is it would be unrealistic to expect the perpetrator to have been able to control their emotions. Due to the ambiguity between murder and voluntary manslaughter, defense attorneys often get murder charges often mitigated to voluntary manslaughter charges for their clients.
One of the most other common justifications for killing include justified self-defense. In most jurisdictions, a civilian has the right to kill another person if they feel that their own life or the life of others would otherwise be in immediate peril. Killing another person under such circumstances is not recognised as homicide in some places, although other places still classify self-defense killings as a form of homicide, or manslaughter.