David Conn speaks to Meredydd Hughes, the current South Yorkshire police chief constable, about the lessons learned from Hillsborough. guardian.co.uk

In a dusty library at the far end of the Houses of Parliament, among 10 boxes of documents relating to the Hillsborough disaster which were made available by the South Yorkshire police following a government order some years ago, is a statement from a police constable on duty that day.

On the front page is a handwritten instruction from a more senior officer. "Last two pages require amending," it notes. "These are his own feelings. He also states that PCs were sat down crying when the fans were carrying the dead and injured. This shows they were organised and we were not. Have [the PC] rewrite the last two pages excluding points mentioned."

As they prepare to mark Wednesday's 20th anniversary of the 1989 FA Cup semi-final between Liverpool and Nottingham Forest, the families of the 96 people who died at Hillsborough retain, with their enduring grief, a burning sense of injustice. The discovery that the police vetted junior officers' statements, and amended many to remove criticisms of the police's own operation, seemed to confirm the families' suspicions after Hillsborough: that the police tried to cover up their own culpability for the disaster. The families are still outraged that after Lord Justice Taylor's official inquiry, a lengthy inquest, high court appeals and a judicial "scrutiny", no one has ever been held accountable, and unanswered questions remain.

In his report, Taylor concluded firmly that police mismanagement of the crowd had caused the disaster. Chief Superintendent David Duckenfield, commanding his first big football match, had agreed to relieve a crush outside the ground by opening an exit gate to allow a crowd of supporters to enter together, rather than singly through the turnstiles. The central pens of the Leppings Lane terrace were full, but no officers were ordered to block the tunnel leading to those pens and direct supporters to the sides, where there was still room. "Failure to give that order," Taylor wrote, "was a blunder of the first magnitude." Taylor criticised South Yorkshire police for refusing to accept that truth. Duckenfield even said originally that supporters forced open the gate; that was condemned as a "disgraceful lie" by Lord Justice Stuart-Smith in his 1998 judicial scrutiny of new Hillsborough evidence. "It is a matter of regret," Taylor wrote, "that ... the South Yorkshire police were not prepared to concede that they were in any respect at fault. The police case was to blame the fans for being late and drunk ... It would have been more seemly and encouraging ... if responsibility had been faced."

Yet at the inquest that followed, prominence was given again to police accounts of supporters being drunk and without tickets. The families were appalled by the eventual verdict of accidental death rather than unlawful killing, and felt that the police force principally responsible for so many deaths had behaved, from the day of the disaster, without humanity. It emerged that two police CCTV videos went missing from the locked control room on the night of the disaster - one showing the police opening the gate survived - and that deepened suspicion.

It was amid that legacy of betrayal that evidence emerged, nine years later, that senior South Yorkshire police officers had vetted and amended their junior officers' statements, in consultation with the force's solicitors, before presenting them to Taylor and the inquest. Criticisms that senior officers failed to provide leadership on the day, and radio communication was poor, were removed from several statements. Accounts of drunken or misbehaving fans, on the other hand, were almost all left in. The junior justice minister, Maria Eagle, MP for Liverpool Garston, said questions still remained about who was involved with that process and how far it went, and she urged the force to "come clean" and make a genuine apology. "The institutional behaviour of South Yorkshire police was appalling," she said. "I stand by the comments I made in the House of Commons at the time. This was a black propaganda unit, engaged in a conspiracy to cover up."

Police documents

Eagle complains the documents were "dumped" in the parliamentary library after South Yorkshire police were ordered to disclose them, and she doubts if it is a comprehensive collection. The 10 boxes are in no discernible order; there is no index or explanatory letter, and it is difficult to believe it can be complete: there are no memos between senior officers, or between the police and their solicitors.

Many statements have apparently not been amended, or the originals are not there. On the ones which have, there are handwritten notes on the front, setting out sections to be changed. There is a list headed Amended Reports, with 163 officers' names on it, and another, with 248 names on it, with a column noting when the statements were vetted.

The police argue they were trying only to cut emotion and opinion out of the officers' raw statements. Stuart-Smith concluded there was no cover-up, because the changes mostly involved removing comment and hearsay, although he did criticise some deletions of fact.

Yet the handwritten note on the front of that PC's statement - "This shows they were organised and we were not" - appears to show there was a more sinister agenda, to undermine the fans and exonerate the police.

Meredydd Hughes, the current South Yorkshire police chief constable, said the force fully accepted Taylor's findings, including the criticism that the police failed to take responsibility and sought to blame the disaster on supporters. He did not, however, accept that the amending of statements was part of that campaign. "It was not a systematic attempt to hide the truth," he said. Hughes said he would find out whether there were further documents which have not been publicly disclosed, make available any not covered by legal privilege, and issue an apology if appropriate.

"We are not about trying to hide things," he said. "We are not the same force that was here in 1989. We exist to protect the public, learn lessons from Hillsborough and put them into practice."

Prof Phil Scraton, author of Hillsborough: The Truth, was the first to discover the changing of statements, and he maintains it was a cover-up. "The statements were transformed after a team of officers, from the force under investigation, reviewed and altered them. If cover-up means anything, this was it."

The emergence of the changed statements is not the worst lingering injustice the families feel. Many are still profoundly scarred by the inquest process, and crucial decisions made by the coroner, Dr Stefan Popper. He held "mini-inquests" while the director of public prosecutions was considering criminal charges against the police officers in command - no charges were ultimately brought.

At the mini-inquests, West Midlands police officers read out summaries of evidence about where and when victims died. Witnesses were not called, let alone cross-examined. Popper then limited the main inquest, which began in Sheffield on 19 November 1990, to events up to 3.15pm on the day of the disaster. He ruled that by then, all the victims had received injuries in the Leppings Lane crush which rapidly caused irreversible brain damage.

That line of reasoning was upheld when the families challenged it by judicial review in the high court in 1993. Yet the "mini-inquests," followed by the 3.15 cut-off, meant two huge areas have been closed from full investigation: the response to the disaster by the police, ambulances, fire service and local hospitals, and the individual circumstances of how each victim died.

A number of witnesses, never called to the inquest, have since bitterly criticised the emergency response. Anthony Edwards, a paramedic in one of only three ambulances that made it on to the pitch out of 42 called to the ground, described the operation as "chaotic". He said that paramedics could not reach the crush, and the "basic technique" of inserting airways into casualties' mouths was barely administered. Another leading ambulanceman, John Flack, said it was "bedlam".

Hillsborough was a scene of horror. Supporters were mostly laid on their backs, rather than in the recovery position, some with clothes covering their faces, even though no qualified person had determined they were dead. There were literally piles of bodies at the Leppings Lane end, and bodies left lying around elsewhere. Only 14 of those who died were taken to hospital, a fact Ann Adlington, solicitor for the Hillsborough Family Support Group, describes as "shocking".

In August 2006, Anne Williams, whose 15-year-old son Kevin was killed at Hillsborough, applied to the European court of human rights, arguing that the inquest into her son's death was "insufficient" due to the 3.15 cut-off.

Over years of tireless campaigning, Williams tracked down people who had helped Kevin, including Derek Bruder, an off-duty police officer, and a woman special police constable. They had testified that Kevin had signs of life up to 4pm; Bruder felt a pulse, and the SPC said Kevin had opened his eyes and said "Mum".

Their statements were changed after visits from the West Midlands police, to suggest there were no signs of life. Both have since emphatically stood by their original statements. Bruder has since complained that his evidence "was not presented in its entirety or in a professional manner" at the mini-inquest, to which he was not called to give evidence in person, and he has emphatically maintained he did feel a pulse. The SPC has also stood by her original statement. Williams sought the opinions of three eminent pathologists, who all disagreed with the diagnosis by the consultant, Dr David Slater, who examined Kevin. Dr Iain West, consultant forensic pathologist at London's Guy's hospital, contested Slater's finding, which had been upheld in the high court, that Kevin had died from traumatic asphyxia. That and crush asphyxia were the causes of death ascribed to all who died at Hillsborough. West said he believed Kevin died from severe neck injuries, and could have been saved had he been treated early enough. There may have been other victims who were recoverable, he said, after 3.15.

Applications to the European court have to be made within six months of exhausting the last possible domestic legal means of redress. The judges took that to be Stuart-Smith's "scrutiny", which upheld the coroner's findings in the case of Kevin Williams and rejected all requests to reopen the inquests. On 17 February this year, the ECHR dismissed Williams's case as out of time. Sitting in her home in Chester, surrounded by files and documents, Williams said: "I won't give up, not until the record is put straight. You can't grieve properly, you can't lay your children to rest, until you have established what really happened."

Meredydd Hughes acknowledged that the police response to the unfolding disaster was "a picture of terrible confusion, a lack of leadership at critical times". Asked whether he could understand the families' frustration with the 3.15 cut-off, he said: "I understand it, but it is not for the police service to comment on."

Margaret Aspinall, vice-chair of the Hillsborough Family Support Group, whose 18-year-old son James died at Hillsborough, said the 3.15 cut-off was "the biggest issue" for the families. "There are huge, unanswered questions. How many could have survived if they had had proper care, and oxygen? Even now, we want reopened inquests beyond 3.15."

The families want answers, too, about the role of a West Midlands police officer, Detective Superintendent Stanley Beechey, whom Popper described as "the second most senior officer at the time of the main inquest".

In June and July 1990, Beechey had been in a monitoring room when Duckenfield and other senior officers were interviewed about their roles at Hillsborough. Beechey was given the sealed audio tapes of the interviews and was responsible for presenting them to the inquest. The coroner said publicly that Beechey had "an awful lot to do" with preparing the evidence summaries for the mini-inquests.

Beechey was a former head of West Midlands serious crime squad, which was disbanded in August 1989 after a string of collapsed cases, and amid allegations of police malpractice. A complaint about Beechey was made to the then Police Complaints Authority by George Tomkins, who alleged he had been "fitted up" by West Midlands police for an armed robbery he did not commit. Tomkins spent 17 months on remand in Birmingham's Winson Green prison before he was acquitted.

The West Midlands chief constable, Geoffrey Dear, moved named West Midlands SCS officers to "non-operational duties". Beechey's transfer was to "studying technical aspects of Hillsborough". Dear said he believed this involved working on fuzzy video footage to enhance its quality. When told Beechey became involved at a senior level, Dear said: "It definitely was not what I had in mind when I transferred him. If I had been told, I would have taken him off the investigation. I wouldn't have had Beechey working on that or any other inquiry. Not because he might necessarily be doing anything wrong, but because it was not appropriate." On 20 June 1990, Beechey was formally interviewed, under caution, about Tomkins's allegations. So, at the same time Beechey had been present at the interviews of senior officers responsible at Hillsborough, he was himself under formal investigation.

Detective's involvement

Beechey was not disciplined following the PCA inquiry, and returned to operational duties on 30 November 1990. His period on "non-operational duties" had taken in the Hillsborough mini-inquests, the criminal inquiry for the DPP, and the first 11 days of the main inquest.

In April 1993, Tomkins took out a private prosecution against Beechey, three other police officers and a DPP lawyer, accusing them of perverting the course of justice. The police officers' cases were committed to the crown court. In 1995 the DPP discontinued the prosecutions. Tomkins took out a civil claim, suing the West Midlands police for malicious prosecution. On 18 March 1996, the force agreed, without admitting any wrongdoing by any officer, to pay Tomkins £40,000 compensation, and £70,000 for his legal costs.

Although there is no evidence that Beechey did anything improper in the Hillsborough investigation, Aspinall feels Beechey's involvement is another area of unease. "We want it cleared up," she argues. "What was this police officer doing on the Hillsborough investigation, what position did he occupy, and why, if he was on 'non-operational duties?'"

A spokesman for West Midlands police provided a statement: "Det Supt Beechey was a later addition to the team of officers who liaised with the Hillsborough coroner, and his role was of a limited, overseeing nature. There has never been any suggestion that he carried out the support work into Hillsborough in anything other than a rigorous, thorough and professional manner. An unconnected civil action brought against DS Beechey was settled in a separate legal process, the basis of which means we cannot comment further."

Hillsborough seems an age away now, a disaster caused by police mismanagement at an unsafe football ground, where the Football Association commissioned a semi-final despite the ground's safety certificate being a decade out of date. In the 20 years since, football grounds have been rebuilt, helped initially by public grants, and the top clubs have made fortunes.

Yet for the families of the mostly young people who died, there has been unending grief, and a traumatic legal ordeal leaving them with questions still unanswered.

"I don't like to use the word justice," says Aspinall. "I prefer to say that we want the full truth, and accountability. Even now, it would make a difference, alleviate some of the hurt and betrayal we have suffered for 20 years."

Unanswered questions

The cause of the Hillsborough disaster - police mismanagement of the crowd - was established by Lord Justice Taylor in his report published just four months afterwards, in August 1989. Yet 20 years on, key questions remain unanswered about the disaster's aftermath.

1 What, in detail, happened after 3:15pm on the day of the disaster?

2 Could more people have been saved if the response to the disaster had been better co-ordinated?

3 Who removed two CCTV video tapes from the locked control room at Hillsborough on the night of the disaster?

4 Why was nobody identified to have removed them, and what investigation was mounted?

5 Which South Yorkshire police officers worked in the unit that vetted police statements before they went to Taylor and the inquest?

6 Who gave the orders for them to do so and what was the stated intention of those orders?

7 Are the documents lodged by order of the government in the House of Lords library a complete archive of South Yorkshire police's Hillsborough documents?

8 What was Det Supt Stanley Beechey, a former head of the West Midlands serious crime squad, doing on the Hillsborough investigation while he had been placed on "non-operational duties"?