FLAUM, Circuit Judge.

This consolidated appeal, involving six separate criminal cases, requires us to resolve what has become known in the Northern District of Illinois as the "grand jury issue." In February of 1987, the office of the United States Attorney discovered that the records of the clerk's office did not contain a written order extending the Special December 1983 Grand Jury beyond its initial 18 month term. Subsequent investigations discovered similar omissions in the records of the Special October 1984 and Special January 1985 Grand Juries.

Several defendants indicted by these bodies contend that their indictments are nullities because the putative special grand juries were not properly constituted when they returned these indictments. The government argues that the omission of a written extension order is not error under 18 U.S.C. § 3331, the statute regulating the summoning and term of special grand juries. We hold that the § 3331 extension provision requires only a judicial determination that a special grand jury has not finished its business. The record indicates that this determination was made prior to all but one period of extension of the affected special grand juries; we cannot ascertain on this record whether the Special October 1984 Grand Jury was properly extended for a second time in October of 1986. Accordingly, we hold that the failure to enter formal written orders of extension was not error, and that the indictments against all of the defendants except Clemenic are therefore valid.

I.

The six cases before us involve the Special December 1983 Grand Jury (the "1983 Grand Jury") and the Special October 1984 Grand Jury (the "1984 Grand Jury"). Chief Judge McGarr ordered the 1983 Grand Jury convened on December 2, 1983. On May 25, 1985, before its original 18 month term expired, the Chief Judge extended the Grand Jury's term pursuant to 18 U.S.C. § 3331. This constituted the first of three such six month extensions authorized by the statute. On November 25, 1985, Chief Judge McGarr again extended the 1983 Grand Jury, this time until June 2, 1986. Prior to the termination of this second extension, the U.S. Attorney never presented, and the Chief Judge never signed, a third formal written order of extension. However, the 1983 Grand Jury continued to meet and return indictments, and was instructed on several occasions by Chief Judge McGarr to "resume deliberations."

Defendants Wilson, Rosenstein and Sanders were each convicted on the basis of indictments returned after the expiration of the 1983 Grand Jury's second six month extension. These defendants contend that the 1983 Grand Jury was not properly extended for the third of its three statutorily authorized extensions. Thus, they allege that its power to return indictments lapsed in June of 1986, thirty months after its impanelment, rather than in December of 1986, a full three years after it was convened.

Defendants Taylor, Nigo-Martinez, Jaraba, and Clemenic were indicted by the 1984 Grand Jury. They contend that this Grand Jury was never validly extended beyond its original 18 month term, and that its power to indict therefore lapsed in April of 1986. The October 1984 Grand Jury was convened pursuant to an order of Acting Chief Judge Marshall. During its first 18 months, the Grand Jury returned indictments against many defendants, including original and superseding indictments against Taylor charging various narcotics-related offenses. In March of 1986, before the expiration of its initial 18 month term, the Grand Jury voted unanimously to continue its work; however, no formal order of extension was ever entered. The 1984 Grand Jury continued to appear weekly before Judge McGarr (and later Judge Grady) until February of 1987, ten months after the end of its initial 18 month term.

After discovering the lack of written orders extending the 1983 and 1984 Grand Juries, the United States Attorney's office prepared corrective orders which Judge McGarr signed. In the case of the Special December 1983 Grand Jury, Judge McGarr issued an order on February 21, 1987 finding that in May of 1986 he had determined that the 1983 Grand Jury had not completed its work. In the case of the Special October 1984 Grand Jury, Judge McGarr issued an order on March 3, 1987 finding that in March of 1986 he had determined that the 1984 Grand Jury had not completed its work. In addition to setting forth Judge McGarr's factual findings, both of these orders purported to amend the records of the respective Grand Juries nunc pro tunc to reflect the entry of the extension orders on the proper dates.

II.

In this appeal, the government first argues that the absence of a formal order extending the Grand Juries was not a defect, because the applicable statute requires only a judicial finding that a special grand jury has not completed its work. Since there is evidence that such a judicial determination was made with respect to both Grand Juries at issue, the government asserts, the indictments and subsequent convictions are valid. Second, even if the absence of a written order is a defect, the government contends that it is a defect in the institution of the proceedings or in the indictment, and any objection was therefore waived under Federal Rule of Criminal Procedure 12(b) because defendants failed to raise this issue before trial. The government asserts that Federal Rule of Criminal Procedure 12(b) creates a distinction between waivable defects in personal jurisdiction, which protects individuals, and nonwaivable defects in subject matter jurisdiction, which restricts the types of cases a court is empowered to hear. The government urges that as long as the indictment charges a federal crime — thereby showing subject matter jurisdiction in the court under Federal Rule of Criminal Procedure 12(b)(2) — it is valid unless the defendant objects to it before trial. Finally, the government asserts that even if defendants could show cause as to why they failed to object prior to trial, any error was harmless in light of defendants' subsequent convictions.

The defendants, some of whom are appellants and some of whom are appellees, contend that no special grand jury is properly extended without entry of an order; that even if a judicial determination is sufficient under the statute, none was made here; that the courts below therefore lacked jurisdiction; that any objections therefore could not have been waived; and that harmless error analysis is inapplicable where jurisdiction is lacking.

Because we conclude that 18 U.S.C. § 3331 does not require a written entry to effect the extension of a special grand jury's term, we hold that as to all but one defendant no error has occurred. We therefore do not reach the waiver and harmless error issues.

III.

The special grand jury is a creature of statute. United States v. Lang, 644 F.2d 1232, 1235 (7th Cir.), cert. denied, 454 U.S. 870, 102 S.Ct. 338, 70 L.Ed.2d 174 (1981). An examination of the language and purpose of 18 U.S.C. § 3331 compels our conclusion that the mere omission to enter a written extension order does not affect the status of an extended special grand jury. The relevant language reads:

The grand jury shall serve for a term of eighteen months. . . . if, at the end of such term or any extension thereof, the district court determines the business of the grand jury has not been completed, the court may enter an order extending such term for an additional period of six months. No special grand jury term so extended shall exceed thirty-six months.

. . . . .

18 U.S.C. § 3331(a). Our approach to interpreting this language cannot be one of "slavish literalism. . . . We reject a view that would make `a fortress out of a dictionary,' remembering instead that `statutes always have some purpose or object to accomplish, whose sympathetic and imaginative discovery is the surest guide to their meaning.'" United States v. Rabb, 680 F.2d 294, 296 (3d Cir.), cert. denied, 459 U.S. 873, 103 S.Ct. 162, 74 L.Ed.2d 135 (1982) ( quoting Cabell v. Markham, 148 F.2d 737, 739 (2d Cir.) (Learned Hand, J.), aff'd, 326 U.S. 404, 66 S.Ct. 193, 90 L.Ed. 165 (1945)). We agree with Judge Plunkett's careful analysis in United States v. Smith, No. 86 CR 272 (N.D.Ill. May 20, 1987), that to extend a special grand jury the statute requires only that the district court overseeing its activities make a determination that the grand jury has not finished its business. If the court finds that the grand jury still has work to do, the statute itself authorizes the extension. The law thus requires only this judicial determination — not the ministerial act of memorializing it by formal order — to effect the valid extension of a special grand jury.

Our interpretation of the extension provision of § 3331(a) is supported by our reading of the statute as a whole. See id., slip op. at 6-7. Although subject to a degree of judicial supervision, § 3331 allows special grand juries substantial independence in fulfilling their duties. This independence is incompatible with a provision that would allow an inadvertent clerical omission to cripple the grand jury. Both sections of § 3331 reflect the special grand jury's relative autonomy. Under § 3331(a), a special grand jury may not be discharged before it has served 18 months unless the grand jury itself determines that it has finished its business, and the judge then enters an order for its discharge. The judge merely ratifies the grand jury's determination. Under § 3331(b), if the judge fails to wait for the grand jury's determination and tries to discharge it early, or if he fails to extend the grand jury's term when its business remains unfinished, the statute protects against his arbitrary or erroneous action. The grand jury by majority vote can appeal the district judge's action or failure to act to the chief judge of the circuit. Pending the chief judge's order, the grand jury continues to serve. Significantly, although § 3331(b) contemplates the entry of an order in the case of the discharge of a grand jury as a final judicial step after the grand jury's own determination has been made, it mentions no such requirement in the case of an extension.

The history and purpose of § 3331 militate against a reading of the statute which would allow the mere failure to enter a formal extension order to prematurely terminate the life of a special grand jury. Our review of the relevant legislative history leads us to adopt Judge Plunkett's analysis in Smith:

The section was enacted as one small part of the Organized Crime Control Act of 1970, and was, like several other of the Act's provisions, designed to provide law enforcement authorities with more effective tools in the fight against organized crime. See Organized Crime Control Act of 1970, Pub.L. No. 91-452, 84 Stat. 923 (1970) (Statement of findings of purpose). Title I of the Act, of which § 3331 is a part, was designed to enhance the powers of grand juries investigating organized crime by ensuring that a sufficient number of grand juries would be available to accommodate the needs of the particular district, by permitting the special grand juries to serve for longer periods, and by giving them a greater degree of autonomy from the courts. [ See 116 Cong.Rec. 35,290, 35,313, 35,321, 35,328, 35,332, 36,293.] While the House version of § 3331 (the version eventually enacted) amended the Senate version to retain some control by the district court over the special grand juries, see H.R. Rep. No. 1549, 91st Cong., 2d Sess. 32, reprinted in 1970 U.S. Code Cong. Admin.News 4007, 4007, it is evident from the debates in the House that a major concern of the drafters was that grand juries be protected against arbitrary termination of their term of service by district courts.

. . . .

The legislative history plainly indicates that § 3331 was enacted to permit the convening of special grand juries which would have significant independent authority to determine the length of their service without interference from the courts. In light of the protections provided these special grand juries against intentional actions taken by the district court to terminate their service before their business had been completed, we conclude that it would be contrary to the spirit as well as the letter of the statute to hold [indictments] invalid . . . because of an inadvertent omission by the district court. Nothing in the legislative history even hints that any provision of § 3331 was designed to protect the individuals investigated by these special grand juries. Cf. United States v. Pisani, 590 F. Supp. 1326, 1339 (S.D.N. Y. 1984). In fact, the entire purpose of the statute is to permit the special grand jury sufficient time to complete [its] investigations of complex matters. We can find no evidence whatsoever in the legislative history that Congress was attempting to legislate the validity of indictments in § 3331. Cf. United States v. Wallace Tiernan, Inc., 349 F.2d 222, 227 (D.C. Cir. 1965); Nolan v. United States, 163 F.2d 768, 769 (8th Cir. 1947), cert. denied, 333 U.S. 846 [ 68 S.Ct. 649, 92 L.Ed. 1130] (1948); Breese v. United States, 203 F. 824, 828 (4th Cir. 1913).

Smith, No. 86 CR 272, slip op. at 7-10 (emphasis added).

Defendants contend that we should follow the decisions of the United States Courts of Appeals for the Ninth and Second Circuits holding that improperly extended grand juries were without power to return indictments. See United States v. Armored Transport, Inc., 629 F.2d 1313, 1316 (9th Cir. 1980), cert. denied, 450 U.S. 965, 101 S.Ct. 1481, 67 L.Ed.2d 614 (1981); United States v. Macklin, 523 F.2d 193, 195 (2d Cir. 1975); United States v. Fein, 504 F.2d 1170, 1173 (2d Cir. 1974). These cases are inapplicable here because we hold that as to all but one defendant, the grand juries were properly extended. Moreover, these cases are inapposite, because they examined grand juries convened under Federal Rule of Criminal Procedure 6(b), which provides for 18 month terms. The grand juries at issue were purporting to act beyond the term authorized by law and their acts were therefore nullities. Here, by contrast, each of the special grand juries was impaneled pursuant to § 3331, which authorizes a 36 month term. All of the indictments before us were returned within this time period.

It would have been preferable for the Chief Judge to enter an order at the time of these special grand juries' extensions evidencing his determination that they had not completed their work. See United States v. Marrapese, 610 F. Supp. 991, 1010 n. 6 (D.R.I. 1985). A written order is the best evidence of a judicial act. But in the absence of a statutory provision requiring the entry of a written order, the judicial determination alone stands as the operative act of the court. Courts accomplish much of their business without formal memorialization. Moreover, the common law distinguishes between the rendition and the entry of judgment. See People v. Redman, 122 Ill.App.3d 787, 462 N.E.2d 21, 24, 78 Ill.Dec. 305, 308 (1984); Freeman on Judgments §§ 46-49 (1925). Cf. Speaks v. Brierley, 417 F.2d 597 (3d Cir. 1969), cert. denied, 397 U.S. 1051, 90 S.Ct. 1388, 25 L.Ed.2d 665 (1970) (policy in favor of maintaining the integrity of written record against subsequent oral inquiry into its meaning); Wigmore on Evidence § 2450 (integration of judicial records compulsory). It is the rendition of judgment that is determinative; entry of a notation is merely ministerial. The judicial act of determining whether a special grand jury has completed its work is separate from and prefatory to the ministerial act which reflects it. "That which the court performs judicially . . . is not to be avoided by the action or want of action of the judges or other officers of the court in their ministerial capacity." Freeman on Judgments § 46. Where a supervising judge has failed to enter a written extension order under § 3331, other reliable and unequivocal evidence that he or she actually made the determination in question may suffice. We therefore proceed to examine the sufficiency of this evidence.

IV.

On February 21, 1987 Chief Judge McGarr signed an order which contained findings of fact and purported to extend the term of the 1983 Grand Jury nunc pro tunc. A court may issue a nunc pro tunc order to correct the record so that it reflects what was actually done but never recorded due to clerical inadvertence. See Recile v. Ward, 496 F.2d 675, 680, modified on other grounds, 503 F.2d 1374 (5th Cir. 1974); Matthies v. Railroad Retirement Board, 341 F.2d 243, 246-48 (8th Cir. 1965). "The office of a nunc pro tunc (`now for then') order is to clean up the records by showing what was previously done with effect from the time done; it is not to alter substantive rights." King v. Ionization Int'l, Inc., 825 F.2d 1180, 1187 (7th Cir. 1987). No formal order was ever entered extending the term of the 1983 Grand Jury; thus the record may not be altered after the fact to show the entry of such an order. Yet, as we have already held, the entry of a formal order was not necessary. We therefore examine Judge McGarr's order solely to determine whether it contains evidence that he made the requisite determination in May of 1986.

Paragraph seven of Judge McGarr's order reads: "I determined prior to May 25, 1986, that the grand jury had additional matters to transact, had not yet completed its business, and should therefore be extended another six months." Judge McGarr's finding is corroborated by the fact that he ordered the 1983 Grand Jury to "resume deliberations" on several occasions in April and May of 1986 and treated it as properly extended. Defendants point out that an assistant U.S. Attorney made a conscious decision not to seek another extension order for the 1983 Grand Jury because he erroneously believed that the previous order, which purported to extend the Grand Jury "until further order of the court," was sufficient. The fact that the U.S. Attorney's office never sought an extension, however, does not contradict Judge McGarr's finding that he was familiar with the work of the Grand Jury and made the requisite determination prior to May 25, 1986.

Judge McGarr made similar findings with regard to the 1984 Grand Jury. Paragraph seven of his March 3, 1987 order states that he "determined in March 1986, that the grand jury had additional matters to transact, had not yet completed its business, and should therefore be extended another six months." Judge McGarr's finding is corroborated by the fact that the 1984 Grand Jury voted in March to continue its work. See supra note 8. This evidence suffices to show that the 1984 Grand Jury was properly extended for six months beyond its original term.

Judge McGarr's order therefore indicates that the 1984 Grand Jury was validly extended until October of 1986. The 1984 Grand Jury, however, continued to sit until February of 1987 — four months beyond its initial extension. The record before us does not reflect whether a judicial determination was made, prior to the expiration of the 1984 Grand Jury's first extension, that it had unfinished business. Further, it is not clear from the record on which date in October, 1984 the 1984 Grand Jury was impaneled. The Grand Jury indicted Clemenic on October 14, 1986, returned a superseding indictment against him on January 6, 1987, and a second superseding indictment on January 13, 1987. We therefore remand Clemenic's case to the district court for a determination of whether his original indictment was returned less than 24 months after the October 1984 impanelment date; and whether there is any evidence that a judicial determination was made prior to the expiration of its first extension that the 1984 Grand Jury had not finished its business.

V.

In summary, we hold that the Special December 1983 Grand Jury was validly extended until December 2, 1986 and the Special October 1984 Grand Jury was validly extended until 24 months from the date of its impanelment. The Grand Juries were thus properly constituted when they returned indictments against defendants Taylor, Nigo-Martinez, Jaraba, Wilson, Rosenstein and Sanders, and these defendants' convictions are not on this account invalid. We remand for a determination of whether, consistent with this opinion, any of Clemenic's indictments were valid.