But Callum's mum, Emma, told the coroner: "Callum was 14, he was very mature. Kids play worse games.
"He was allowed to play Call of Duty but not other games. Does that make me a bad parent?"
Callum was found hanging by his school tie from his bunk bed after he was grounded by his mother following a row.
Before he died at his home near Stockport, Greater Manchester, in March last year, Callum had been in his bedroom playing on a computer.
His family said they believed he was using Facebook or YouTube.
But when Mr Pollard asked Callum's mother, Emma Green, about her son playing Certificate 18 Call of Duty, which has sold 100 million copies worldwide, she became upset, admitting she had known of the age restriction.
Callum used to play the Activision war game, which has graphic scenes of killings, with his stepfather, David White.
In one sequence, gamers see a hanging man.
Recording an open verdict, Mr Pollard told the court: "Age limitations on these various computer games are there for a valid reason. It is very important young children don't play them."
The inquest also heard the teenager told his 13-year old girlfriend he wanted to run away and have a baby with her.
Mr Pollard added: "Callum decided he was going to put the tie around his neck. "Was that with the intention of killing himself or just to give you a shock? We don't know."
Do you think the coroner is right to make this connection or just heaping more grief on the mother?
Do your pre-18 teens play Call of Duty?