Plans for the 1989 FA Cup semi-final at Hillsborough required double the maximum number of Liverpool supporters to pass through the Leppings Lane turnstiles, a court has heard.
On the tragic day, 10,100 Reds fans were directed through seven turnstiles – an average of 1,443 people per turnstile.
A build up of people outside the stadium prompted a gate to be opened to let them in, which caused a crush in pens 3 and 4 of the West terrace.
A 1986 Safety Guide stipulated a safe limit was 750 per hour.
“It is not merely with hindsight that we can look back and realise there was a serious risk of death”, the prosecution said.
The “obvious or readily discoverable” danger meant the failure of police match commander David Duckenfield was “so very very far from good enough”, the jury was told.
Mr Duckenfield, 74, denies the charge of manslaughter by gross negligence of 95 Liverpool supporters.
The court heard Chief Superintendent Duckenfield had the “keenest” view of the crowded pens from his position in the police control box.
Footage was also shown of Tottenham supporters climbing over a fence to escape a crush in the same pens during the 1981 FA Cup semi-final between Tottenham and Wolves.
After the match a letter from South Yorkshire Police to Sheffield Wednesday described their actions as “not only necessary, but vital to avoid further serious injuries and save life”.
It went on to say the club and the police “should be able to improve” their crowd control in future.
By 1989 Sheffield Wednesday’s stadium Safety Certificate was “very out of date” having not been updated since it was awarded in 1979, the jury was told.
An expert had estimated the capacity of the Leppings Lane terrace should have been reduced from 7,200 to 5,426 to ensure safety.
Sheffield Wednesday’s Safety Officer at the time, Graham Mackrell, is charged with breaching regulations by failing to agree the methods of admission and not taking reasonable care in the drawing up of contingency plans.
The 69-year-old denies the charges.
The prosecution is continuing to open its case against both men in a trial that is expected to last up to four months.
Hillsborough’s 96th victim, Tony Bland, is not included on the indictment because the law at the time prevented a manslaughter charge being brought if the death occurred more than a year and a day after the incident.