A knockout (sometimes abbreviated as K.O.) is the act of rendering a person unconscience through non-lethal means.
The act of knocking out an individual is a non-lethal way of dealing with a person. When the affected individual is knocked out, their body will go limp and they will then be unconscious. Knocking out someone can be caused by a number of things: through physical striking with the fist, a chokehold, environmental objects or even from something that falls on them from above (like another person).
In the Tom Clancy's Splinter Cell series, knocking out a person is an alternative to simply killing them (although killing an enemy has no penalties and are just as quiet as non lethal methods). This can however be a mission-critical feature as killing innocent police officers or civilians may result in mission failure. Unconscious guards can be woken up by other patrolling guards, so hiding their sleeping body is key to remaining undetected. In Tom Clancy's Splinter Cell: Chaos Theory and Tom Clancy's Splinter Cell: Double Agent (Version 2), it is possible for the player to be knocked out by the guards (some guards fire Sticky Shocker rounds at the player). After being hit, the player's screen will transition to black and they will find themselves being interrogated by the guards.
In most games, if the player shoots the knocked out body, the NPC will be counted as dead and the player has made a kill; in Chaos Theory, if Sam grabs someone that mission demands him to terminate, both actions will be lethal, alternatively, if the mission demands zero fatality, both actions will be non-lethal.
- The only game to not feature any non-lethal functions the player can readily use is Tom Clancy's Splinter Cell: Conviction, every enemy is killed some way or another when grabbed by the player. There are some exceptions for pre-set interactions with NPCs, like when Sam Fisher spared Andriy Kobin after his interrogation.
- There are some instances where the player is forced to only use 'non-lethal' means in Conviction. The first instance is in the campaign level 'Lincoln Memorial', where the player 'knocks out' police officers as they chase after Galliard's killer.
- The second instance is in the cooperative campaign where Archer and Kestrel have to knock out police officers who are breaching the building.
- It is possible for unconscious enemy to die by drowning if they are placed in an area of water. This can be evidenced by observing them using Thermal vision. For players looking for non-lethal outcomes, it is advised to not hide unconscious bodies near areas of water. In Blacklist, the knocked out enemies can be killed by high falls, the kill will not count though.