Police scandal! What springs to mind this week? Undercover officers stealing the identities of dead children? The Stephen Lawrence case? Officers taking bribes from journalists?

But shift your attention from London to Cardiff, because this week the latest chapter in one of the gravest and most shameful police scandals of the last half-century has just unfolded.

It is more than 25 years since Lynette White, a young sex worker, was murdered in Cardiff, a victim of more than 50 stab wounds. At the time, the only evidence was that a dark-haired, blood-stained white man with cut hands had been seen near her flat shortly after the killing. Eight people, seven of them black, were eventually arrested. All were tested for blood found at the scene of the murder but with no positive result. Five were charged. Three were convicted in 1990. All were innocent.

The so-called Cardiff Three – Tony Paris, Stephen Miller and Yusef Abdullahi – were eventually freed on appeal in 1992 after the shoddy nature of the case against them was exposed. It was not until 2003 that the real murderer, Jeffrey Gafoor, confessed to carrying out the killing alone.

A scandal indeed. But who has been punished for the false imprisonment of the three? Two other vulnerable sex workers, Leanne Vilday and Angela Psaila, and a neighbour of White's, Mark Grommek, who had made statements to the police implicating the men, were charged with perjury. During their own trial in 2008, they claimed they had been harassed into lying by the police. The judge, Mr Justice Maddison, accepted that and told them: "You were seriously hounded, bullied, threatened, abused and manipulated by the police … as a result of which you felt compelled to agree to false accounts they suggested to you." He added that what they had been subjected to was "unacceptable in a civilised society". He jailed them for 18 months.

The following year, 13 former and serving South Wales police officers were charged with perverting the course of justice in connection with the case. It was to be the largest police corruption trial ever to take place in a British court. Eight of them, and two civilians, stood trial in 2011 in Swansea crown court; a further trial of the others was due to follow. All pleaded not guilty. In December 2011, the trial was abandoned on the grounds that documents essential to the case, which should have been disclosed to the defence, had been destroyed. The defendants, including those yet to stand trial, were formally declared not guilty. Amazingly, not long after the abandonment of the trial, it emerged that the documents had not been destroyed at all.

Two inquiries, by the Independent Police Complaints Commission and HM Crown Prosecution Inspectorate were launched into how this happened. This week, their reports were published. The conclusions make depressing reading. The Crown Prosecution Service says it accepts that "some elements of disclosure were not adequately managed from the outset, leading to the prosecution team of police and prosecutors being overwhelmed by the scale and complexity of the disclosure exercise".

The chief constable of South Wales police, Peter Vaughan, has welcomed the conclusions into the handling of the latest prosecution, saying, "It is clear from the reports that there was no misconduct on the part of officers and prosecutors". What South Wales police might add, perhaps, is a full apology to the wrongly convicted men and to Lynette White's family – whom the South Wales police, by their shocking behaviour, had so dismally failed in a case that has so far cost around £30m. (If you want the full story, read Satish Sekar's The Cardiff Five: Innocent Beyond Any Doubt.)

The lawyer representing the wrongly accused, Kate Maynard, says that the reports expose "a disturbing degree of complacency and incompetence on the handling of disclosure by the prosecution team".

The home secretary, Theresa May, has until 16 September to decide whether to keep this case open with a public inquiry. Sometimes such a course of action is just another way of shuffling off a problem, but this case must be kept alive. Tony Paris says that the conclusions of the reports make him feel that he was "let down by the system all over again". He was.

Two of his five co-defendants have already died. Justice should not be allowed to die with them.