The move follows difficult negotiations between the CPS and chief constables and represents a significant response to Court of Appeal hearings such as the Birmingham Six and Judith Ward cases.
In many cases, information obtained by the Crown and not presented to the court was withheld from defence lawyers, even though it was of assistance to them.
Additionally, a ruling by Lord Lane, the former Lord Chief Justice, in one of the West Midlands Serious Crime Squad cases has now placed police under an obligation to reveal disciplinary findings against officers so that the CPS can decide whether fresh cases in which they are involved should go ahead or be dropped.
Barbara Mills QC, the Director of Public Prosecutions, has warned police that they have a duty to disclose and the onus is on prosecutors to decide if any unused material should be withheld.
The new instruction echoes a recent speech to senior officers where she said: 'We may find some of the rulings on disclosure hard to live with on a daily basis, but we must observe them. We have no choice. If in doubt, disclose to us. We will not automatically disclose to the defence. We must, however, know what exists before we can make an informed judgement . . . we must know, or the case may go horribly wrong later and an important prosecution may fail.'
Despite cases like Judith Ward, the instruction is based on the appeal by Ernest Saunders over the Guinness prosecution, which supported the widest definition of 'unused material'.
The instruction says it is impossible to list all types of documentation, but unused material should be disclosed, 'unless it is plainly of no interest or value'. CPS sources say this should include all police documents such as computer records, messages, observation logs, crime reports, police injury claims, photofits in addition to notes and scientific reports.Reuse content