“ If their production before the grand jury violated Perlman's constitutional right then he could protect that right only by a separate proceeding to prohibit the forbidden use. To have denied him opportunity for review on the theory that the district court's order was interlocutory would have made the doctrine of finality a means of denying Perlman any appellate review of his constitutional claim. Due regard for efficiency in litigation must not be carried so far as to deny all opportunity for the appeal contemplated by the statutes. ”

“ That a grand jury proceeding has no defined litigants and that none may emerge from it, is irrelevant to the issue. The witness' relation to the inquiry is no different in a grand jury proceeding than it was in the Alexander case. Whatever right he may have requires no further protection in either case than that afforded by the district court until the witness chooses to disobey and is committed for contempt. See Hale v. Henkel, supra, and Wilson v. United States, supra. At that point the witness' situation becomes so severed from the main proceeding as to permit an appeal. ”

“ It is the means for achieving a healthy legal system. As an instrument of such policy the requirement of finality will be enforced not only against a party to the litigation but against a witness who is a stranger to the main proceeding. Neither a party nor a non-party witness will be allowed to take to the upper court a ruling where the result of review will be 'to halt in the orderly progress of a cause and consider incidentally a question which has happened to cross the path of such litigation * * *.' Mr. ”

“ To be effective, judicial administration must not be leaden-footed. Its momentum would be arrested by permitting separate reviews of the component elements in a unified cause. These considerations of policy are especially compelling in the administration of criminal justice. ”