Victims in hundreds of crimes were wrongly told that their offender could not be brought to justice.
The Crown Prosecution Service refused to bring charges in 315 cases that eventually did go to court and ended in guilty verdicts.
Families only got justice by using the Victims’ Right to Review Scheme, allowing a second opinion. Ex-Victims Commissioner Vera Baird called our findings “shocking”.
Figures show that of 560 cases sent to court since the review scheme started in 2013, more than half (315) ended with a conviction, with acquittals in the other 245.
Seven of the successful cases involved deaths, plus 59 sex cases, 12 frauds and 150 violent crimes.
Mrs Baird warned the problem could be worse because the CPS sometimes drops cases at the late stage in court to get a formal not guilty verdict.
She said: “That means the case can’t be re-opened even if the Right to Review succeeds.
“These figures may merely be the tip of an iceberg of bad decisions by the CPS.”
Criminals successfully prosecuted under the review scheme include knife killer Geoffrey Strike, 76, who admitted the manslaughter of Jason Comerford, 21, in Manchester.
His family had waited 26 years for justice.
Recycling boss Stephen Jones, 60, got nine years for gross negligence manslaughter over a baling machine accident at his firm in Kimnel Bay, North Wales which led to the death of Norman Butler, 60.
The CPS said of around 2,000 Right to Review cases per year, one in eight went before a court.
A spokesman added: “More than 97% of our decisions are not appealed. Right to Review was designed to make sure our decisions can be scrutinised. We are committed to learning lessons from successful appeals.”