Crowd Science

Module 8, lesson 3 · 60 minutes

Hillsborough, 1989

Pens certified for more than they could safely hold, a gate opened without flow control, and twenty-seven years before inquests said what had happened.

You’ll be able to

  • reconstruct the capacity arithmetic of pens 3 and 4 and explain why opening Gate C was dangerous before anyone came through it;
  • describe the mechanism, including what is still contested about how quickly people died;
  • follow the inquiries from 1989 to 2021 and say what each found, and read the disaster through DIM-ICE.

Introduction

Here are three numbers. Pens 3 and 4 at the Leppings Lane end of Hillsborough Stadium were certified to hold 2,200 people between them. When the Health and Safety Executive recalculated their capacity after the disaster, it reached 1,693, and said even that should be reduced further. At about 14:52 on 15 April 1989, an exit gate, Gate C, was opened, and about 2,000 people came in.

You do not need to know anything else to see the shape of the problem. More people came through that one gate than the HSE thought the two pens could safely hold even when empty. And the 2016 inquests found that the pens were not empty: they were already full before Gate C was opened. 97 people died.

What happened

The match was an FA Cup semi-final between Liverpool and Nottingham Forest. The crush happened in pens 3 and 4 of the Leppings Lane end. The fact sheet does not give a full minute-by-minute timeline, and this lesson does not reconstruct one beyond what the sources state.

  1. Before about 14:52. Pens 3 and 4 fill. The inquests found they were already full before Gate C opened.
  2. About 14:52. Exit Gate C is opened. About 2,000 people come in.
  3. In the pens. People are crushed. The Taylor report describes some “held upright by pressure all round”, and, when a barrier broke, “Many fell and the involuntary rush of those behind pressed them down”.
  4. The toll. 94 people died on the day and three more later, including Lee Nicol in hospital and Andrew Devine in July 2021, whose inquest on 28 July 2021 found he had been unlawfully killed, “the 97th fatality”. 766 people were injured, according to a secondary source.

The space: capacity arithmetic

Pens are fenced sections of a standing terrace. They divide a crowd so that pressure in one section cannot spread to the next, which also means a full pen cannot relieve itself sideways. The capacity of each pen therefore matters on its own.

The Leppings Lane end, as far as the course’s sources describe it. Capacities from the 1987 certification drawing and the HSE’s 1990 recalculation; Gate C from ; barrier test load from the Taylor report. Schematic, not to scale.
Pens 3 and 4: two capacitiesCertified capacity from the 1987 Eastwood & Partners drawing; HSE recalculation by Collins and Waterhouse, January 1990.
PenCertifiedHSE recalculationCertified ÷ HSE
Pen 31,2008221.46
Pen 41,0008711.15
Pens 3 + 42,2001,6931.30

Work through what the table means.

  1. The certificate was 30% too high overall. 2,200 ÷ 1,693 ≈ 1.30. Pen 3 alone was certified for 46% more than the HSE’s figure. And the HSE said its own 1,693 should be reduced further, because of six departures from the Green Guide.
  2. A full pen at the certified figure was over capacity. If the pens held their certified 2,200, they held 507 more people than the HSE’s maximum. Recall from m7-l3 that the Green Guide’s holding capacity is area ÷ 10 × D, with D at most 47 per 10 m². Exceeding the recalculated capacity by 30% means 30% more people per square metre than the HSE judged appropriate for those pens.
  3. Gate C’s inflow exceeded the pens’ safe capacity on its own. About 2,000 people came in. Even had pens 3 and 4 been empty, that is more than 1,693.

That last point is the expert reading. Opening a gate is a decision about flow, and flow needs somewhere to go. Opening Gate C without controlling where the people coming through it went sent a large inflow towards spaces that, the inquests later found, were already full. In the language of m1-l5, the outflow from the pens was close to zero, so nearly the whole inflow accumulated as density.

The mechanism

Hillsborough was a standing crush: compression in an upright crowd pressed against a barrier or a fence, with a collapse inside it. The Taylor Interim Report gives the cause of death: “In virtually every case the cause of death was crush asphyxia due to compression of the chest wall against other bodies or fixed structures so as to prevent inhalation.” Some people died upright, held by pressure all round; others fell when a barrier broke and were pressed down. Mechanisms mix, as m2-l2 warned.

Barriers and forces

Crush barriers are rails across a terrace meant to break up the forward pressure of a standing crowd. The Taylor report quotes the test load for them: “an evenly distributed force of 6.0kN/metre width to be applied for 3 five minute periods”. So a barrier 3 m long is tested at 18 kN.

Do not read that as a limit on what a body can bear. It is a test of a structure. For bodies, the biomechanical model of Kroll, Still and colleagues gives about 1,000 N as a safe static chest force. The barrier test is about eighteen times that over 3 m, because it is meant to hold back many rows of people at once. That is the point of m2-l1: at high density, forces from many rows add up, and the people at the front, against the barrier or the fence, carry them.

6.0 kN/m is a barrier test load (Taylor, para 238). The “6,227 N” sometimes quoted is a force on a person from a 1993 study known only through Still’s website. They measure different things and should never be merged.

How quickly people died: a contested question

The Taylor Interim Report said: “If no relief came in four minutes there would be irreversible brain damage; if longer, death.” For years that framed the medical evidence: a fast, uniform death that no response could have prevented.

In 2012 the Hillsborough Independent Panel cast “significant doubt on the single unvarying pattern… of traumatic asphyxia causing unconsciousness within seconds, followed inevitably by death within a few minutes”. It found that 28 victims did not have traumatic asphyxia with obstruction of the blood circulation, and that in 31 the heart and lungs had continued to function after the crush. That matters for what the emergency response could have achieved, and it is why the course treats “death within minutes” as contested for Hillsborough.

Pen 3 was certified for 1,200 people; the HSE later put its capacity at 822. If pen 3 held its certified number, by what factor was its density above the HSE’s safe maximum? And why does a fence between pens make this worse rather than better?

1,200 ÷ 822 ≈ 1.46, so the density was about 46% above the HSE’s maximum. Pens are fenced to stop pressure spreading across the terrace, but that also stops the crowd in a full pen moving sideways into emptier space. The only relief is backwards or forwards, and with people arriving from behind and a fence in front, there is none.

What the inquiries found

Hillsborough has the longest investigative history of any case in this module. Read it in order, because each stage revised the one before.

From 1989 to 2021Dates and findings as reported by the sources cited in each row.
WhenBodyWhat it found or decided
August 1989Taylor Interim Report“the main reason for the disaster was the failure of police control”. The date is given as 1 or 4 August.
19 January 1990Taylor Final Report76 recommendations, including all-seater stadiums: the top two divisions by August 1994 (the lower two were exempted in July 1992).
31 January 1990HSE report (Collins and Waterhouse)Recalculated pens 3 and 4 at 1,693 against a certified 2,200.
12 September 2012Hillsborough Independent PanelCast significant doubt on the assumed medical pattern of rapid, inevitable death.
26 April 2016InquestsUnlawfully killed (by a 7–2 majority). Errors by the police, the ambulance service and the club, and the stadium’s design and certification, caused or contributed; supporters’ behaviour did not; the pens were already full before Gate C was opened.
2019Criminal trialsDavid Duckenfield was found not guilty at a retrial (28 November 2019); Graham Mackrell was convicted under the Safety of Sports Grounds Act 1975.
26 May 2021Criminal trialThe trial over the alleged cover-up collapsed.
28 July 2021InquestAndrew Devine unlawfully killed, “the 97th fatality”.

The inquest finding on supporters is the one to hold on to. The jury was asked whether supporters’ behaviour caused or contributed to the dangerous situation, and found that it did not. It took twenty-seven years to reach that finding about a disaster in which the space was over capacity and a gate was opened into it. Any explanation that looks first to the crowd’s behaviour, rather than to the space and how it was managed, is the panic myth of m3-l1 in another form. Still’s general observation fits: “when you analyse the facts the crowd is rarely the cause of major incidents”.

What changed

  • All-seater stadiums. Taylor’s final report led to all-seater grounds in the top two divisions by August 1994. Seats fix the number of people in an area and stop forward pressure from building down a terrace.
  • A regulator. The Football Spectators Act 1989 created the Football Licensing Authority (section 8), which became the Sports Grounds Safety Authority in 2011.
  • Barrier testing. The Taylor report sets out the test load for crush barriers quoted above.

What did not change by statute is just as instructive. The certificate that allowed 2,200 people into pens 3 and 4 was issued under the system created after Ibrox (m8-l2). A licensing regime protects people only if the capacities it certifies are right and are checked against the ground as it actually is.

Through the DIM-ICE lens

Hillsborough failed in ingress, in normal mode, on all three influences, and then failed again in emergency mode. The matrix is the course’s reading of the findings above; red marks a failure the inquiries found contributed.

Run the three counterfactuals from m8-l1. Correctly certified pens would not have made opening Gate C safe unless the flow through it went somewhere else. Control of that flow would not have made over-certified pens safe. And neither helps people who cannot see that the space ahead of them is full. Each failure removed a margin that the others relied on.

  • “The crowd caused it.” The 2016 inquests found supporters’ behaviour did not cause or contribute to the dangerous situation.
  • “Everyone died within four minutes, so nothing could have been done.” The Independent Panel cast significant doubt on that pattern; in 31 victims the heart and lungs continued to function after the crush.
  • “The 6 kN/m barrier test is what a person can survive.” It is a structural test load over a metre of barrier, not a force on a chest.
  • “The ground had a safety certificate, so its capacities were safe.” The certified figure for pens 3 and 4 was 30% above the HSE’s recalculation.