Assumed cheating

Assumed cheating is an evidentiary status defined by FIDE's fair play rules. It arises when a validated algorithm or methodology analyzes a game, series of games, or tournament and produces a statistical result above the official threshold.

The analysis uses a statistic called a Z-score. In plain terms, it measures how far the observed performance lies from the model's projection for comparable players. An extreme enough result can trigger the presumption, but it does not mean that every move matched the first choice of a chess engine, a program that calculates moves, or that any brilliant performance is suspicious.

When proceedings are opened under this rule, the player must provide an explanation capable of rebutting the presumption. The case still includes evidence review and a right to respond. A signal from Fair Play software should not be described as an automatic conviction or a final public finding of cheating.