David Duckenfield, the South Yorkshire police officer in command during the Hillsborough disaster, lacked knowledge of the “hazards” at the stadium’s Leppings Lane end that represented “an obvious, serious and very present risk of death”, his trial for manslaughter has heard.

Chronic overcrowding in the central “pens” on the terraces at that end of Sheffield Wednesday’s stadium during the 1989 FA Cup semi-final caused a crush that killed 96 people.

Richard Matthews QC told the jury at Preston crown court on Wednesday, the second day of the trial, that David Duckenfield – promoted and appointed match commander shortly before the semi-final on 15 April 1989 – did not know how 24,500 Liverpool supporters were to gain access to the ground, through only 23 turnstiles.

Matthews also said Duckenfield failed to identify the “obvious hazard” of overcrowding and crushing posed by the layout of the turnstiles and concourse immediately inside the ground, and the central pens three and four of the Leppings Lane terraces, which were divided by metal fencing and had a high fence at the front.

“A failure to have that knowledge is so extraordinarily bad,” Matthews said, “it’s such an extraordinary failure, because such personal knowledge, you may think, is obviously central and essential to discharging the responsibility of match commander.”

Duckenfield, now 74, sat in the court, not the dock, alongside Graham Mackrell, 69, the former Sheffield Wednesday secretary and safety officer, who is accused of two criminal breaches of safety legislation relating to the arrangements for the 1989 semi-final.

Matthews took the jury through a history of changes to the Leppings Lane end, which were made after Tottenham Hotspur supporters suffered crushing at the 1981 FA Cup semi-final against Wolverhampton Wanderers. Police at that match guided some Tottenham supporters out of the terraces, to sit around the perimeter of the pitch.

After that incident, the Leppings Lane terrace was divided into pens and Matthews said expert evidence will be given that the division reduced the terrace’s safe capacity from 7,200 – the figure stated on the Hillsborough safety certificate – to 5,246.

Of these changes to the capacity and confined layout of the pens, Matthews said: “The scene was almost literally set for … the subsequent failures by David Duckenfield and Graham Mackrell.”

Mackrell is accused of failing to agree with police, as required by the safety certificate, a change to how Liverpool supporters were admitted to the Leppings Lane end compared with the semi-final the previous year, which was also between Liverpool and Nottingham Forest.

The change meant that in 1989 all 10,100 people with tickets to stand on the Leppings Lane and North West terraces had to be admitted through seven turnstiles. That was an average of 1,443 supporters through each turnstile, whereas almost three times the number of turnstiles were available for Nottingham Forest supporters, at 468 people each.

Matthews said that Duckenfield’s “first extraordinarily bad failure” was not to be fully aware of how the Liverpool supporters were to be admitted from the “bottleneck” of the Leppings Lane: “It was so very far from good enough or sufficient to be simply aware that 23 turnstiles were going to serve the entry of 24,000 people.”

Duckenfield should have been aware of the safety risks, Matthews said, partly due to a general warning in the 1986 “Green” Guide to Safety at Sports Grounds, of “the potential scale of death and injury at a crowded sporting event.” He said that the risk of death at Hillsborough did not need hindsight after the disaster to be identified; “personal knowledge” of the match commander would have recognised it in the arrangements of the turnstiles, and the tunnel across the concourse that led directly to the confining central pens.

“The Crown say that the risk of death was obvious, serious and present throughout the failings of David Duckenfield to show reasonable care in discharging his duty as match commander,” Matthews said.

The criminal charge against Duckenfield – of causing the deaths by gross negligence manslaughter – relates only to 95 of the people who died. The 96th, Tony Bland, suffered critical brain damage and died four years later, when life support in hospital was lawfully withdrawn. The law in 1989 stipulated that no charges relating to a death could be brought if the victim died longer than a year and a day after the alleged criminal acts.

Both Duckenfield and Mackrell have pleaded not guilty in pre-trial hearings. The trial continues.