Was my opponent using a computer?

Hello. I've recently played a game for my school chess team. This game was played online because of covid. I suspect my opponent could have used a computer. Overall he had a 98.2 accuracy. My opponent was white.

Here's the game: https://www.chess.com/a/2WYo8cDUakoYa

Fun to finally have one of these we can actually discuss, since it happened off site.  When people raise this issue on this site, they are almost always just sore losers, but in your case with it happening at an online tournament, its natural to wonder if there weren't proctors monitoring people through the camera like they do it for money online tournaments.  

I'm going to say no, he wasn't cheating, or at least you'll certainly not prove he was.  He certainly played some odd and bad moves that were not recommended by the computer like 15. g3.  And there was no brilliant tactics or anything like that on his part.  Rather, you were basically equal, but selected the wrong move at several places and it eventually hurt you.  

15. g3 is recommended by the computer though. Chess.com actually says it's the best move....

What engine are you running that likes 15. g3?  Letting the chess.com version of stockfish running on your home computer run, 15. g3 never comes up.  Its certainly a weird looking move that is hard to understand a human coming up with.  29. a5 also struck me as a bit weird, and I did see that the chess.com stockfish liked that for a second, even if it quickly becomes the distant third choice.  Still, a5 does have a logic to it.  Rg6 leading to the win of the queen was a bit clever, but I don't think spotting it is suspicious.

The difficulty here is that we are speculating that maybe your opponent was running a weak engine for only a little bit of time, and how likely is that?  What was the time control?

The time control was 30+5.

Is a 98.2 accuracy a normal occurrence?

I am not an expert to tell whether 15 G3 was good or not. But I guess the people commenting on this thread must know that there are smart cheaters who don't follow each and every move recommended by the engine....they follow it upto a certain point and once they get a considerable advantage they purposely throw in a bad move....so that it becomes difficult for the cheat detect system to track them.

I definitely agree. I'm pretty sure my opponent stopped playing engine moves in the endgame because at that point he had a pretty good advantage. I don't think I can ever prove that he used a computer though.

Yes unfortunately you won't be able to prove it ...even if he did. But I believe the cheat detection system will catch him eventually ...how much ever smart he is.....

Personally even I feel he did get some outside assistance...I don't think so 1400 players can play that well.

15.g3 was the first move i thought of in that position.  Why?  Glad you asked.  Black has the DSB, so place your pawns on dark squares. 

The a4-b4 pawn pushes make perfect sense as white has the 4-3 pawn queenside pawn majority. 

But without knowing the true strength of both players, its impossible to tell if their was any "outside interference".

I would say both players are around 1400-1600

Unfortunately, without actual camera footage, you'll never discover a good cheater. Not at that level.

My first instinct is that he wasn't cheating. Most cheaters would play out the opening with the engine, since they can always claim they prepared the line or whatever. Yet the Bg5 Bxf6 maneuver is rather amateurish.

The position was relatively equal, but black played some odd moves and I'm not shocked he lost. Even once the two rooks for the queen trade happened it wasn't over. But going passive with the queen to defend b7 was the nail in the coffin.

Whites accuracy was high, for sure. But I've gotten accuracy that high in three minute blitz games. It's not unheard of, and whites play was very easy. Black didn't really put pressure on him.

Moves like h3 are suspicious. It's not obvious, but not impossible for him to see. It's not the best move, but an odd one he could throw in the confuse accusers, yet still maintains a winning position.

Could he have been cheating? Sure. Was he? Well...if he was cheating he's very good at it. I'll never play an online tournament game for this reason (unless there's some verification method).

The fact is, we will never really know--which is why it would have been more ethical for you to remove your opponent's name from the game before making a public accusation. 

As to the game itself, there are certainly no smoking guns. This was a very quiet opening, so a high degree of accuracy is no surprise. Neither side was called upon to make any difficult decisions. White's 12.Bxf6 was a bit of a surprise, and certainly not the computer's first choice. In fact, the game was pretty dull until Black's 20...e5 and 22...Bc3 worked out badly for him. 

Also, calling your opponent a "1400 player" is pretty misleading. He had only been a member of that site since October 5, and new members start with a provisional rating of 1500. His only two rated games were with you: one win, one loss. You have no idea what his real strength is.

The level of cheating, especially since this killer virus has been ridiculous.  I will no longer play any type of serious online chess.  The only thing i will play (at work) is 3/2, and even then the level of cheating is stupid.  And throw in those that blatantly acknowledge they cheated, just ruins online chess for me.

I am not a terribly strong player, but I have 96+ percent accuracy in several games. The one common thread is that my opponents never put any real pressure on me. It's not hard to be pretty damn accurate if no one is shooting back!

My play is like a shotgun.  I dont need to be accurate, when i have a wide spread pattern.

"My play is like a shotgun.  I dont need to be accurate, when i have a wide spread pattern."

I have to agree with that!

What was he rated?

Kg2, h3, and a5 are all moves that I would probably never consider. But then again I am much lower rated.