Game concept
Prevented Murder
The game also links it as Prevent.
From the game's encyclopedia
Rarely, certain situations in the life of the Target of a Murder may cause the Scheme to fail in the final stages of its execution.
This overrides Success Chance.
Examples include intervention by a bodyguard, a foodtaster, a shieldmaiden, or a loyal pet.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Prevented Murder is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Rarely, certain situations in the life of the Target of a Murder may cause the Scheme to fail in the final stages of its execution." It is part of Scheme. The game also links it as Prevent. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.