Humberside Police had been tasked with investigating a series of stranger rapes in North East Lincolnshire, including an attack on a woman as she was walking home in 2015.
The woman had reported to police that she was held down by one man as another raped her in an alleyway.
But a disciplinary hearing was told that one officer, named only as Officer D, watched CCTV footage recovered in the case at an inappropriately high speed - despite expressly being told how not to speed it up - and a card game, either Solitaire or Freecell, was seen in his computer's task bar.
Officer D later told bosses that nothing had distracted him from his work.
The officer, who denies three allegations of misconduct, could lose his job if the allegations are proven.
John Whittaker, representing Humberside Police, said Officer D had been asked to review CCTV picked up as part of the investigation into the rape of the woman as she walked home from Cleethorpes town centre.
He was later tasked with a further review of the CCTV after a suspect had been arrested.
But Mr Whittaker said the officer had failed to identify the victim in the company of two suspects on some of the CCTV recovered.
He said: “It wasn’t a difficult task.”
The panel heard evidence from Det Con Dean Stevens, who specialised in the technology involved in CCTV.
He said he gave specific instructions to Officer D on how to watch some footage recovered from a petrol station.
He said it would be acceptable to watch this at either normal speed or twice normal speed, but any faster and the system would lag, meaning the footage would freeze on screen and key evidence might be missed.
He said he left the officer to watch the footage and later returned.
He said: “When I came back, I saw on the screen he was looking at the footage at an unacceptable speed.
“Not just on normal time, or one setting up, it was faster than that.
“Straight away, I said to Officer D, ‘You run the risk of missing something’.”
He said he also saw that a card game had been running on the computer.
Michael Rawlinson, representing Officer D, asked whether Det Con Stevens knew for sure that Officer D had not been playing the game during a break.
Det Con Stevens said he did not know this for sure.
The panel heard that later checks on CCTV recovered from local businesses revealed footage of the victim in the company of two men, one of whom was on a BMX-style bicycle with distinctive spokes.
Detectives gave evidence saying if they had known earlier that one suspect was on a distinctive bicycle, they could have issued a public appeal for information.
The hearing was told that one suspect had been arrested and charged but had claimed that sex with the complainant had been consensual.
Officer D is accused of submitting an internal report stating he had reviewed all the CCTV in the case when it was evident he had failed to identify the victim and two suspects on the footage.
Secondly, he is also accused of viewing one part of the CCTV at an inappropriately high speed and while playing computer games.
Thirdly, he is accused of stating that he had contacted the Crown Prosecution Service about a case when this was untrue.
Officer D denies all the allegations and is due to give evidence today.