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"neither the doctrine of separation of powers, nor the need for confidentiality of high level communications, without more, can sustain an absolute, unqualified presidential privilege of immunity from judicial process under all circumstances. The President's need for complete candor and objectivity from advisers calls for great deference from the courts. However, when the privilege depends solely on the broad, undifferentiated claim of public interest in the confidentiality of such conversations, a confrontation with other values arises. Absent a claim of need to protect military, diplomatic or sensitive national security secrets, we find it difficult to accept the argument that even the very important interest in confidentiality of Presidential communications is significantly diminished by production of such material for in camera inspection with all the protection that a district court will be obliged to provide.
The impediment that an absolute, unqualified privilege would place in the way of the primary constitutional duty of the Judicial Branch to do justice in criminal prosecutions would plainly conflict with the function of the courts under Art. III.
Since we conclude that the legitimate needs of the judicial process may outweigh Presidential privilege, it is necessary to resolve those competing interests in a manner that preserves the essential functions of each branch.
A President and those who assist him must be free to explore alternatives in the process of shaping policies and making decisions and to do so in a way many would be unwilling to express except privately.
But this presumptive privilege must be considered in light of our historic commitment to the rule of law. . . . We have elected to employ an adversary system of criminal justice in which the parties contest all issues before a court of law. The need to develop all relevant facts in the adversary system is both fundamental and comprehensive. The ends of criminal justice would be defeated if judgments were to be founded on a partial or speculative presentation of the facts. The very integrity of the judicial system and public confidence in the system depend on full disclosure of all the facts, within the framework of the rules of evidence.
In this case we must weigh the importance of the general privilege of confidentiality of Presidential communications in performance of the President's responsibilities against the inroads of such a privilege on the fair administration of criminal justice.
We conclude that when the ground for asserting privilege as to subpoenaed materials sought for use in a criminal trial is based only on the generalized interest in confidentiality, it cannot prevail over the fundamental demands of due process of law in the fair administration of criminal justice. The generalized assertion of privilege must yield to the demonstrated, specific need for evidence in a pending criminal trial."
http://www.landmarkcases.org/nixon/opinion.htmlThe decision was unanimous with the exception of MR. JUSTICE REHNQUIST, who recused himself.