A trout in the milk?

I can’t tell you why the Armenian grandmaster Tigran Petrosian was found guilty of cheating last month, because I don’t know. The event was the 2020 PRO Chess League, an online team event organised by Chess.com. Petrosian (not to be confused with his namesake, who was World Champion in the 1960s) was playing for the Armenia Eagles, who appeared to overcome the St Louis Archbishops by 9.5-6.5 in a David and Goliath final. Petrosian’s 3.5/4 score against the mighty Archbishops’ squad (including wins against Fabiano Caruana, Wesley So and Leinier Dominguez) was exceptional. After his games were investigated and the results overturned, the title (and $20,000 first prize) was re-awarded to the team from St Louis.

In recent years, forensic statistical analysis of chess games has become a niche area of research. With the right software, one can dissect an entire collection of games, measuring each move against the suggestions of a powerful chess computer.