[oehpr]

I mean, such a system already exists when players do analysis of their matches. The thing that makes a move identifiable as a blunder is that a chess engine evaluating the board before and after the move.

It's also worth keeping in mind that you will sometimes see players match the best engine move 95% of the time or more at the 800-1000 elo's and they're not cheating, it's just their opponent is blundering and the next move is obvious.

So specifically, you have to find when players matched up with engine moves, where the engine decided on an optimal move by looking far into the future.