There are some disgraceful miscarriages of justice in every democratic developed nation of the world, the worst of which are on a par with the greatest excesses of the worst dictators; it is only the scale of suffering that might be reduced, not the actual suffering.
In 1975 Earl Truvia and Gregory Bright were convicted of murder on the testimony of one eyewitness. The eye witness was schizophrenic and a heroin addict. These facts were kept from the defence team. In 2002 Mr Truvia and Mr Bright were exonerated from their convictions, the court having decided, rightly, that had the eye witness’s history been known they would never have been convicted.
They sued the New Orleans district attorney but lost, the Supreme Court holding that the case had not been proved. There is very little in the way of sanction or compensation that exists to make prosecutors across the world follow the rules of justice.
In the United Kingdom, where similar rules about disclosing evidence apply, there have been many cases where evidence has been withheld.
Of course it is just that the guilty are convicted, and equally just that the innocent are acquitted. In order to convict the guilty and acquit the innocent it is necessary that the defence not only have all the information that the prosecution have gathered, but also a proper opportunity to digest it, understand it and test it.
They rarely have such an opportunity these days. The prosecution has huge resources: the defence has merely the resources that an accused person may muster, which may have taken a lifetime to accumulate and which almost never come within a fraction of the resources of the prosecution, with their almost limitless access to lawyers, forensic services, and money to investigate.
The gap between the resources of the prosecution and the resources of the defence will widen in time as governments seek to balance the books; very few complain that defence funding has been cut, unless and until it affects them personally.