Tens of thousands of files are sent back to police every year by prosecutors for failing to contain vital evidence.
At least a third of police files prepared for prosecutors are returned because they contain significant mistakes, such as failing to include key witness statements or evidence such as CCTV, statements from victims, or details of special measures needed for vulnerable witnesses.
In the Metropolitan Police, two thirds of files are sent back, according to figures from the Crown Prosecution Service. The force insists that the situation has improved in recent months.
The mistakes often lead to delays in the court process, which criminal lawyers say is unfair to victims and defendants as well as placing an additional burden on the public purse.
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