B The Judicial Assumption of Responsibility for the Public Interest
For our purposes, the account of this subject may conveniently begin with the decision of Duncan v Cammell Laird in 1942.” In 1939, a submarine, which was being constructed by the respondents for the admiralty, sank during submergence tests. Ninety-nine men lost their lives and their families brought actions for negligence against the respondents. The plaintiffs sought discovery of documents concerned with the construction of the submarine but objection was taken by the respondents. The first Lord of the Admiralty submitted a claim for Crown privilege stating that disclosure of the information in those documents would be injurious to the public interest. It is, of course, understandable that in war time the courts should refuse to sanction the disclosure of information about the country’s naval capabilities, when to do so might undermine the country’s war effort. What is, however, far less commendable is the ruling of principle.
At the outset of his speech, Lord Simon LC made clear that he regarded the issue in the case to be one of ‘high constitutional importance.’  Indeed, the House of Lords pronounced a principle justifying this assessment. It held that:
The principle to be applied in every case is that documents otherwise relevant and liable to production must not be produced if the public interest requires that they should be withheld. This test may be found to be satisfied either (a) by having regard to the contents of the particular document, or (b) by the fact that the document belongs to a class which, on grounds of public interest, must as a class be withheld from production.
Equally important, the House of Lords held that: ‘an objection validly taken to production on the grounds that this would be injurious to the public interest is conclusive.’
Thus, the House of Lords established two principles: that the interests of litigants must give way to the interest in secrecy and that ministers are the sole judges of what is in the public interest. Having installed the executive arm of government as judge of the public interest, the House of Lords went on to indicate how it expected the executive to fulfil this function. It would not be proper ground for claiming immunity, the House of Lords indicated, that the documents were state documents, nor that disclosure might reveal inefficiency and lay the government open to criticism. A minister, the House of Lords pronounced, ‘ought not to take the responsibility of withholding production except in cases where the public interest would otherwise be damnified, e.g. where disclosure would be injurious to national defence, or to good diplomatic relations, or where the practice or keeping a class of documents secret is necessary for the proper functioning of the public service.’
There is, however, one point to be made in mitigation for the ruling in Duncan v Cammel Laird. At the time, no orders for discovery could be made against the Crown, so that had the submarine plans been in the possession of the Crown there would have been no basis whatever to compel their production. This position was only to change five years later by the Crown Proceedings Act 1947. However, as might have been foreseen, the hope expressed by the House of Lords that ministers would exercise a fair and disinterested judgment in matters affecting their own government and their own departments was bound to be disappointed. Having been given the freedom to judge and execute the public interest, ministers developed a practice of claiming privilege as a matter of course. If disclosure of the contents of a particular document was not likely to injure the public interest, refuge could be taken in the claim that the class to which it belonged needed secrecy for the sake of the proper functioning of the public service. Similarly, if privilege could not be claimed for a class, there was always the possibility that it could be asserted on account of the sensitivity of the particular document.
The class claim became the most popular with ministers. A practice arose of issuing certificates claiming class immunity on a regular basis, ‘as if pronouncing a spell.’ The standard justification for class immunity was that it was required in order to enable civil servants and ministers of the Crown to express themselves candidly on matters of public administration. Disclosure in the courts, it was said, would inhibit candour. In this way, immunity from production could be secured for ever widening classes of material, even if the subject matter had nothing to do with security, the prevention of crime or sensitive economic matters. It could be claimed for matters such as correspondence regarding the lease of a hotel, or documents concerned with the reorganisation of local authorities, and many others besides.
The courts became alarmed by the extent to which access to evidence was being blocked by ministers of the Crown on grounds of privilege and by their own inability to exercise supervision over the validity of claims to Crown privilege. This alarm resulted in the watershed decision in Conway v RimmerP Lord Morris did not conceal his disenchantment with the existing law when he said that a system under which evidence could be withheld from the court on the say so of a minister was ‘out of harmony with the spirit which in this country has guided the ordering of our affairs and in particular the administration of justice.’  ‘I cannot think,’ Lord Reid added, ‘that it is satisfactory that there should be no means at all of weighing, in any civil case, the public interest involved in withholding the document against the public interest that it should be produced.’ As a result, the House of Lords established three principles of great constitutional importance.
First, it held that the responsibility for deciding whether or not evidence should be withheld from a court of law rested with the courts and not the Crown. It was for the courts to determine whether the public interest necessitated suppression of evidence and, therefore, the matter was not one of Crown privilege. Henceforth a claim for withholding evidence was to be referred to as a claim for public interest immunity. If a minister, or anyone else for that matter, wished to withhold evidence on the grounds that the public interest so demanded, an application would have to be made to the court stating the grounds for the claim. It was then for the court to decide whether to accede to the application.
Second, the House of Lords laid down the process of reasoning which should be followed in the exercise of the judicial discretion to sanction the withholding of evidence. In arriving at its decision, the court has to weigh the public interest in the suppression of evidence against the public interest that the administration of justice shall not be frustrated. This balancing exercise requires the court to place on one side of the scales the potential harm to the public from the disclosure of the evidence in question. On the other side of the scales, the court has to place the consequences to the court’s ability to administer justice, if the evidence were to be suppressed. This last aspect requires the court to take account two separate, if closely related, factors. It requires the court to consider the likely effect that the absence of the evidence might have on the court’s facility to ascertain the true facts. It also requires the court to take into account the effect that the withholding of the evidence will have on the appearance of justice and on confidence in the judicial system. It has been insufficiently appreciated that the need to conduct a balancing act in respect of every claim for immunity has greatly reduced the significance of the distinction between contents claims and class claims. Whether it is claimed that the contents of a particular document is sensitive and its disclosure would, per se, be harmful, or whether it is claimed that, notwithstanding the innocuousness of the information, it is desirable to maintain the confidentiality of the class to which it belongs, the court must consider whether the actual information in question is of importance to the determination of truth before it can allow the information to be withheld.
The third principle has to do with inspection. As we have just observed, the balancing exercise necessitates an assessment of the effect that the absence of a
piece of information might have on the determination of truth. This raises the question: how is the court to determine the likely effect that the evidence would or would not have if it has been withheld? Mindfiil of this difficulty, the House of Lords held that a court was entitled to inspect in private materials for which immunity has been claimed for the purpose of deciding whether or not their suppression would have an adverse effect on the ascertainment of truth.
The Conway v Rimmer decision represents a bold and progressive step in the direction of establishing government accountability for the suppression of evidence. It took decisions in the matter away from ministers and placed them in the hands of the judiciary. Furthermore, it established an even-handed process for determining the issue of suppression of evidence. One particular implication of this process is of great importance. It stands to reason that the effect that the suppression of a piece of evidence would have on the court’s ability to determine the truth would vary according to what that evidence is and according to how it relates to the rest of the evidence. It therefore follows that there can be no a priori answer to the question: would the suppression of the evidence be injurious to the ascertainment of truth? Whether or not it will be injurious will depend on the evidence in question and the circumstances of the particular case. Accordingly, the Conway v Rimmer balancing exercise requires the court to consider the question afresh in every case where a claim for immunity has been made. It cannot rely on precedent in this regard any more than it can rely on precedent when it is asked to decide whether a piece of evidence has sufficient bearing on a particular issue.
We may refer to the need for decisions on a case-by-case basis as the fact- dependent dimension of the balancing process. A judge faced with a claim for public interest immunity cannot accept the minister’s certificate without question. Nor can he rely on precedent to decide for him. Precedent may help him identify what claims can be considered as valid claims. For example, precedent may indicate that maintaining the confidentiality of communications between civil servants and their ministerial masters is in the public interest, or that the desire to avoid criticism does not serve the public interest. But precedent cannot, in the nature of things, have anything to say about the effect that the withholding of a particular piece of evidence would have on a particular issue in a particular case. The scrutiny of claims for public interest immunity, it follows, has to take place every time a claim is made.
The assumption of responsibility for deciding whether evidence should be withheld has had crucial implications for ministerial responsibility. When a minister’s certificate was conclusive, the minister had to consider, at least in theory, what effect his certificate would have on the administration of justice. Under the new dispensation, ministers are relieved of this responsibility. For them it is only to decide whether they believe that the disclosure of the evidence would be harmful to the public interest. If it would be, they may claim immunity. It is then for the court to decide whether to accept the claim or overrule it, depending on the outcome of the balance of interests carried out by the judge. Ministers who appeared in the Scott enquiry were therefore correct in asserting that the responsibility for the suppression of evidence rested with the courts. Their task has been confined to determining whether there are grounds for believing that disclosure would be injurious to the public interest and to asserting that this is the case by issuing a certificate to this effect.  It is not for them to contemplate, let alone decide, what effect suppression might have on the case of the litigant demanding disclosure; if only because the potential effects could only emerge from a review of all the evidence in the case which ministers are in no position to conduct.
Lastly, the Conway v Rimmer strategy mitigated the injustice inherent in the trumping of private interest by the public interest. It was certainly in the public interest that the submarine plans should not be disclosed in the Duncan v Cammel Laird litigation. But was it also right that the dependents of the ninety-nine workmen who died in the accident should be deprived of the means of proving the wrong and risk going without compensation? Under the Duncan v Cammel Laird philosophy, this injustice was tolerated without question. Under the new approach the potential for injustice must be taken into account and counted against the suppression of the evidence.
  1 All ER 587. For a discussion of the legal and historical background, see Jacob, Privileged Crown to Interested Public’  PL 121.
 id at 588.
 id at 592.
 id at 595.
 The House of Lords embraced the pronouncement to this effect made in The Zamora  2 AC 77, 107. Canadian courts have resisted following this decision: see Sopinka, Lederman and Bryant, The Law of Evidence in Canada (Toronto: Butterworths, 1992) 784 — 786.
 id, n 11 above at 595.
 See Jacob, ‘The Debates Behind an Act: Crown Proceedings Reform, 1920—47’  PL 452.
 See judicial dictum referred to in n 45 below.
 Merricks v Nott-Bower  1 All ER 717, 722.
 Re Grosvenor Hotel, London (No 2)  3 All ER 354.
 Wedneshury Corpn v Ministry of Housing and Local Government  1 All ER 186.
 See instances referred to in the cases cited in the preceding two footnotes and instances listed in Phipson on Evidence (London: Sweet & Maxwell, 12th ed, 1976) para 564.
  1 All ER 874. For a discussion of the implications of this decision, see Zuckerman, Privilege and Public Interest in Tapper (ed), Crime, Proof and Punishment: Essays in Memory of Sir Rupert Cross (London: Butterworths, 1981) 248; De Smith and Brazier, Constitutional and Administrative Law (London: Penguin, 1989) 639 — 641.
  1 All ER 890.
  1 All ER 882.
 The distinction is discussed in McNicol, Law of Privilege (New South Wales: The Law Book Co, 1992) 384.
 This decision gave expression to the courts’ wider policy of extending their powers to review administrative decisions. Other key decisions were Ridge v Baldwin  2 All ER 66 and Padfield v Ministry of Agriculture 11968] 1 All ER 694. See Craig, Administrative Law (London: Sweet & Maxwell, 2nd ed, 1989) 203; Cane, An Introduction to Administrative Law (Oxford: Clarendon Press, 2nd ed, 1992) 27.
 Tomkins, Public Interest Immunity after Matrix Churchill  PL 530.
 [19721 2 All ER 1057.