Torture is the act of deliberately inflicting severe physical or psychological pain and possibly injury to an organism, usually to one who is physically restrained or otherwise under the torturer's control or custody and unable to defend against what is being done to him or her. Torture has been carried out or sanctioned by individuals, groups, and states throughout history from ancient times to modern day, and forms of torture can vary greatly in duration from only a few minutes to several days or even longer. Reasons for torture can include punishment, revenge, political re-education, deterrence, interrogation or coercion of the victim or a third party, or simply the sadistic gratification of those carrying out or observing the torture. The need to torture another is thought to be the result of internal psychological pressure in the psyche of the torturer. The torturer may or may not intend to kill or injure the victim, but sometimes torture is deliberately fatal and can precede a murder or serve as a form of capital punishment. In other cases, the torturer may be indifferent to the condition of the victim. Alternatively, some forms of torture are designed to inflict psychological pain or leave as little physical injury or evidence as possible while achieving the same psychological devastation. Depending on the aim, even a form of torture that is intentionally fatal may be prolonged to allow the victim to suffer as long as possible (such as half-hanging).