Evidence and disclosure

Criminal proceedings

MI5 officers may be called as prosecution witnesses in criminal trials, and our intelligence may be admitted in evidence or disclosed to the defence. To date, this has occurred mostly in the context of our counter-terrorism work. 

Our greater involvement in criminal proceedings means that we keep in mind the needs of both the law of evidence and the Crown’s duty of disclosure when we plan and carry out intelligence investigations which may lead to a criminal prosecution. Because our intelligence could be admitted as evidence in court and to ensure compliance with the relevant legislation, we keep detailed records of our operations. 

Judges have allowed our staff to give evidence anonymously and from behind screens. These arrangements are similar to those made for undercover and specialist police officers and members of the Special Forces when giving evidence. The decision on these issues rests with the trial judge in each case. The evidence given by MI5 witnesses is subject to cross-examination by the defence in the normal way, even where the judge makes an order to protect the witness’s identity. 

As for intelligence that is not relied on by the prosecution in evidence but which is potentially relevant to the case, the duty of prosecutors to review such material and to disclose it to the defence if it is reasonably capable of undermining the prosecution case or assisting the defence case applies equally to MI5 material.

Protecting sensitive information 

Courts recognise that the duty to disclose intelligence must be balanced against the need to protect sensitive information. In a criminal case the prosecutor will consider our records and advise which information meets the threshold for disclosure to the defence. If that information is sensitive, such as details of a sensitive investigative technique, its disclosure could cause real damage to the public interest in the protection of national security. In such cases, the prosecutor may apply to the judge to withhold the material. Such applications take the form of a claim for public interest immunity (PII). 

Claims for PII in relation to MI5 material are made by a Secretary of State, usually the Home Secretary. They will carry out a careful balancing exercise, weighing up the competing public interests of the administration of justice and the protection of national security. This exercise takes account of detailed advice from prosecuting Counsel on the relevance of the material to the issues in the case. 

If the Home Secretary considers that the balance favours non-disclosure, a claim for PII will be made. But the decision on a PII claim is ultimately one for the trial judge alone. The courts, not MI5 or the government, ultimately decide what must be disclosed in a particular case. If a claim is accepted, the judge will nevertheless continue to keep the decision to authorise non-disclosure of the sensitive material under review throughout the proceedings. 

Proceedings arising out of disruptive measures recommended by MI5 

Ministers will use legal powers to protect national security, for example by ordering the deportation of a suspected terrorist or placing someone under Terrorism Prevention and Investigation Measures (TPIMs). Such decisions are often based on MI5 intelligence, and MI5 will present the intelligence as evidence in the event that the decision is challenged in the courts, usually the Special Immigration Appeals Commission (SIAC) or the High Court. 

In such cases the court will use special procedures that enable it to take account of sensitive evidence, including intelligence material. Where evidence is not sensitive, the court sits in "open" session. The subject of the decision and their lawyers may take part in the normal way and members of the public may also attend. 

However, the court will use "closed" sessions to hear evidence that the court agrees must be withheld from the subject in order to avoid damage to the public interest, for example, to national security. The subject and their lawyers, and the public, are excluded from closed sessions. Instead, a "special advocate" drawn from a panel of security-cleared counsel represents the subject’s interests. The special advocate may make submissions and cross-examine witnesses in the same way as the subject's own lawyer in open session. 

MI5 officers have given evidence in many such cases in both open sessions (when they are screened in order to protect their identities) and closed sessions. 

Civil proceedings 

A PII claim may be made to protect sensitive information in civil cases, in the same way as in criminal cases. Additionally, there is provision for the court to order a closed material procedure in certain civil cases, which ensures that sensitive material can be considered as part of the case while also being adequately protected. This enables MI5 to rely on sensitive material in our defence when we face actions for civil damages, providing the judge is satisfied that a closed material procedure is necessary to ensure the fair and effective administration of justice. Special advocates may be appointed to represent the interests of claimants in closed material procedures. 

Where MI5 holds material that is relevant to a public inquiry, we will disclose the material with necessary redactions. However, where the material is too sensitive to be disclosed, we will apply for a “restriction notice” under the Inquiries Act so that it is only considered by the Inquiry Chair and their team in a closed session. 

MI5 material relevant to the circumstances of a death may need to be considered in inquest proceedings. In these cases MI5 will work closely with counsel to the inquest to ensure all such material is identified and shown to the coroner to ensure they are properly informed and the proceedings are conducted fairly. A PII claim may be made to protect sensitive material from disclosure to the interested persons. If sensitive material needs to be put into evidence, the Secretary of State may decide that an inquiry should be established in place of the inquest to permit this to happen in closed session.