Public interest immunity

●  Public interest immunity (PII) is a common law doctrine whereby potentially relevant evidence may be excluded at trial.

●  If PII is applied neither party may use the evidence, preserving equality of arms.

●  Exclusion of evidence on grounds of PII is a recognition of the public interest in non-disclosure, which outweighs that of access to evidence of the parties to the proceedings.

●  The principle mainly relates to non-disclosure of documents rather than oral testimony.

●  A claim for non-disclosure may be made by the parties, by the court, or by third parties, including the state or a public body.

●  Non-disclosure claims may be made for a specific document (contents claim) or a series of documents (a class claim).

●  Areas of public interest which are covered by possible PII claims include national security, defence and foreign policy, the identity of police informers, protection of children, and confidential records held by public bodies.

●  PII claims primarily occur in civil cases. The main area in criminal cases is the protection of informers.

●  In criminal proceedings disclosure is governed by the Criminal Procedure and Investigations Act (CPIA) 1996 (as amended by the Criminal Justice Act 2003) and the Criminal Procedure Rules 2018.

●  In civil proceedings disclosure is governed by the Civil Procedure Rules (CPR) 1998.