with whom The Chief Justice, Mr. Justice Blackmun, and Mr. Justice Rehnquist join, concurring in part and dissenting in part.
I agree with the majority that the authorization by the Executive Assistant to the Attorney General of the application for the October 16 interception order contravened 18 U. S. C. § 2516 (1) and that the statutory remedy is suppression of all evidence derived from interceptions made under, that order. I therefore join Parts I, II, and III of the opinion of the Court/ For the reasons stated below, however, I dissent from the Court’s conclusion, stated in Part IV of its opinion, that evidence *549obtained under the two “pen register”1 extension orders and under the November 6 extension of the interception order must also be suppressed.
These are the pertinent facts. On October 8, 1970, the Chief Judge of the United ¡States District Court for the District of Maryland authorized the use of a pen register devieé to monitor and record for a 14-day period all numbers dialed from a telephone listed to respondent Giordano. There is no dispute that the pen register order was based on probable cause and was therefore lawful under the Fourth Amendment. On October 16, 1970, the District Court issued an order authorizing the interception of wire communications to and from Giordano’s telephone for a period not to exceed 21 days. There is likewise no dispute that the wiretap order was based on probable cause. The defect in the application for this order was not the strength of the Government’s showing on the merits of its request but the authorization of the application by the Executive Assistant to the Attorney General rather than by one of the officials specifically designated in 18 U. S. C. § 2516 (1) . As a result of this procedural irregularity both the contents of communications intercepted under the October 16 wiretap order and any “evidence derived therefrom” must be suppressed. 18 U. S. C. §§ 2515 and 2518 (10) (a).
The authorization for use of the pen register device was extended by orders dated October 22 and Novem*550ber 6, 1970. On the latter date the. District Court also extended the intercept authority for a maximum additional period of 15 days.' All three extension orders were based in part, but only in part, on evidence' obtained under the invalid wiretap order of October 16. The wiretap extension order, unlike the original intercept order, was not marred by the defect of improper authorization. . '
The Government contends that, putting aside all evidence derived from the invalid original wiretap order, the independent and untainted evidence submitted to the District' Court- constituted probable cause for issuance of both pen register extension orders and the wiretap extension order, and in the latter case also satisfied the additional requirements imposed by 18 U. S. C.. §2518 (3).2 Preoccupied with the-larger issues in the case, the District. Court summarily dismissed this contention insofar as it related to the pen register extension orders:
“The subsequent extension orders are not supported by sufficient showings .of probable cause, *551however, for the reason that information wa,s used to obtain those extension orders from a Title III wiretap which, for reasons appearing later in this opinion, was defective, The ‘fruit of the po.sonous tree’ doctrine requires the suppression of all pen register information obtained under the subsequent orders. Nardone v. United States, 308 U. S. 338 .., (1939); 18 U. S. C. § 2518 (10) (a).” 340 F. Supp. 1033, 1041 (Md. 1972).
The Court of Appeals did not mention the point. 469 F. 2d 522 (CA4 1972).
With respect to the wiretap extension, neither the District Court nor the Court of Appeals addressed the Government’s contention that communications intercepted under the extension were not derivatively tainted by the improper authorization defect in the original wiretap order, and neither cflurt made any finding on this contention. The District Court simply found the wiretap extension order invalid on a different ground applicable both to the extension and to the original order. Specifically, the court concluded that the original wiretap order was unlawful because the application for it misidentified the approving officer and therefore failed' to comply strictly with the provisions of 18 U. S. C. §§2518 (l)(a) and (4)(d). The misidentificatioh problem occurred in the application for the original wiretap order and in the application for the wiretap extension. The District Court held the extension order invalid on that basis alone and ordered the evidence obtained pursuant thereto suppressed for that reason.3 The Court of *552Appeals affirmed on a different ground entirely. It held the original order invalid because the application for it had been approved by the Executive Assistant to the Attorney General rather than by one of the officials designated in 18 U. S. C. § 2516 (1). The defect of improper authorization, unlike the misidentification problem, arose only in connection with the original wiretap order. Perhaps through simple oversight, the Court of Appeals failed to consider the fate of the evidence obtained under the extension. Thus-neither of the lower courts ruled on the derivative evidence question.
Today we affirm the suppression of evidence obtained under the original wiretap order for the same reason adopted by the Court of Appeals — the defect of improper authorization. As noted above, this defect did not occur in the application for the wiretap extension • order. Today we also hold that misidentification of the approving authority does not render inadmissible evidence obtained pursuant to a resulting interception order. United States v. Chavez, post, p. 562. This decision removes the sole basis advanced by the District Court for suppressing the telephone conversations intercepted under the wiretap extension order and requires us to consider whether that evidence should be suppressed by reason of the improper authorization of the application for the original order. In doing so it is important to note that we are the first court to consider this aspect of the case.
The majority holds that the invalidity of the original wiretap order requires suppression of all evidence *553obtained under the three extension orders. In my view the application to this case of well-established principles, principles developed by the courts to effectuate constitutional guarantees and adopted by Congress to effectuate the statutory guarantees of Title III, demonstrates that the majority’s conclusion is error. As will appear, the same analysis governs all three extension orders, but it may clarify my position to deal with the two pen register extension orders in Part I, below, and to reserve discussion of the November 6 extension of the wiretap for Part II.
I
The installation of a pen register device to monitor and record the numbers dialed from a particular telephone line is not governed by Title III. This was the conclusion of the District Court in the instant case and of the courts in United States v. King, 335 F. Supp. 523, 548-549 (SD Cal. 1971), and in United States v. Vega, 52 F. R. D. 503, 507 (EDNY 1971). This conclusion rests on the fact that the device does not hear sound and therefore does not accomplish any “interception” of wire communications as that term is defined by 18 U. S. C. § 2510 (4) — “the aural acquisition of the contents of any wire or oral communication through the use of any electronic, mechanical, or other device” (emphasis added).. Any doubt of the correctness of this interpretation is allayed by reference to the legislative history of Title III. The Report of the Senate Committee on the Judiciary in discussing the scope of the statute explicitly states “[t]he use of a ‘pen register,’ for example, would be permissible.” S. Rep. No. 1097, 90th Cong., 2d Sess., 90 (1968).
Because a pen register device is not subject to the provisions of Title III, the permissibility of its use by law enforcement authorities depends entirely on com*554pliancé with the constitutional requirements of the Fourth Amendment.4 In this case the Government secured a court order, the equivalent for this purpose of a. search warrant, for each of the two extensions of its authorization to use a pen register. The District Court Seemed to assume that because these extension orders were based in' part on tainted evidence, information obtained pursuant - thereto must necessarily be suppressed under the “fruit of the poisonous tree” doctrine. 340 F. Supp., at 1041. That is not the law.
The District Court relied on Nardone v. United States, 308 U. S. 338 (1939). In that decision the Court held that a statutory prohibition of unlawfully obtained evidence encompassed derivative evidence as well. But the Court also reaffirmed that the connection between unlawful activity and evidence offered at trial may become “so attenuated as to dissipate the taint,” id., at 341, and thait facts improperly obtained may nevertheless be provéd if knowledge of them is based on an independent source. Ibid. In its constitutional aspect, the principle is illustrated by Wong Sun v. United States, 371 U. S. 471 (1963). It is, in essence, that the derivative taint of illegal activity does not extend to the ends of the earth but only until it is dissipated by an intervening event. Of course, the presence of an independent source would alwáys suffice.
The independent-source rule has as much vitality in the context of a search warrant as in any other. Thus, for example, unlawfully discovered facts , may serve as. the basis for a valid search warrant if knowledge of them *555is-obtained from an independent and lawful source. See, e. g., Anderson v. United States, 344 F. 2d 792 (CA10 1965). The obvious and well-established corollary is that the inclusion in an affidavit of indisputably tainted allegations does not necessarily render the resulting warrant invalid. The ultimate inquiry on a motion to suppress evidence, seized pursuant to a 'warrant is not whether the underlying affidavit contained allegations based on illegally obtained evidence, but whether, putting aside all tainted allegations, the independent and' lawful information stated in the affidavit suffices to show probable cause. James v. United States, 135 U. S. App. D. C. 314, 315, 418 F. 2d 1150, 1151 (1969); United States v. Sterling, 369 F. 2d 799, 802 (CA3 1966); United States v. Tarrant, 460 F. 2d 701, 703-704 (CA5 1972); United States v. Koonce, 485 F. 2d 374, 379 (CA8 1973); Howell v. Cupp, 427 F. 2d 36, 38 (CA9 1970); Chin Kay v. United States, 311 F. 2d 317, 321 (CA9 1962).5 Judge *556Weinfeldraptly stated the. point in United States v. Epstein, 240 F. Supp. 80 (SDNY 1965):
“There is authority, and none to the contrary, that when a warrant issues upon an affidavit con- ' taining both proper and improper grounds, and the proper grounds — considered alone — are more than .sufficient to support a finding of probable cause, inclusion of the improper grounds does not vitiate the entire affidavit and invalidate the warrant.” Id., at 82. *
I know of-no precedent holding to the contrary.6
,.. The application of this principle to the pen register extension orders is clear beyond doubt. The original pen register order was based on a showing of probable *557cause made prior to, and therefore undeniably independent of, the invalid wiretap. The affidavit supporting the first extension of the pen register order incorporated the allegations contained in the affidavit submitted. for the original order and provided the additional- untainted information that Giordano had sold heroin to a narcotics agent on October 17, 1970. The affidavit for the second extension of the pen register .order is not included in the record, but there is no reason to doubt that it made a similar incorporation by reference of the earlier,, untainted allegations. I would hold the evidence obtained under the first pen register extension order admissible and remand the case-for determination of whether evidence obtained under the second extension should be admitted as well. ’
The.basis for the majority’s conclusion to the contrary is far from apparent. In the final footnote to its opinion, the Court states that the evidence obtained under the' defective original wiretap order “should be considered a critical element in extending the pen register authority.” The majority does not suggest, however, that the original pen register order was based on anything less than probable cause. Nor does it deny that the affidavit suppor bing the extension of the pen register authority fully incorporated the earlier untainted allegations. And, fin; idly, the majority does not contradict the established principle that a warrant based on an affidavit containing tainted allegations, may nevertheless be valid if the independent and lawful information stated in the affidavit shows probable cause. In light of these significant silences, the majority’s bare assertion that the tainted evidence ob-' tained under the original wiretap order was a “critical element” in the extension of the pen register authority is, to me, an unexplained conclusion — not a rationale.
*558II
Unlike the pen register extensions, the wiretap extension order of November 6 is governed by Title III. The provisions of that statute prescribe an elaborate procedure for the lawful interception of . wire communications. To the extent that the statutory requirements for issuance of an intercept order are nonconstitutional in nature, the exclusionary ‘rule adopted to effectuate the Fourth Amendment does not pertain to their violation. The statute, however, contains its own exclusionary rule, 18 U. S. C. § 2518 (10) (a), and the scope of the suppression remedy is defined by 18 U. S. C. § 2515 to include derivative evidence:
“Whenever-any wire or oral'communication has been intercepted, no part of the contents of such communication and no evidence derived therefrom may be received in evidence in any trial . . .
The "obvious and familiar model for the statutory ban on the use of- derivative evidence was the constitutional doctrine of the “fruit of the poisonous tree,” and the legislative history confirms that Congress intended the phrase “no evidence derived therefrom” to incorporate that doctrine and render it applicable to certain statutory violations of nonconstitutional dimensions. The Senate Report makes the point explicitly:
“[Section 2515], largely reflects existing law. It applies to suppress evidence directly (Nardone v. United States, 302 U. S. 379 (1937)) or indirectly obtained in violation of the chapter. (Nardone v. United States, 308 U. S. 338 (1939).) There is, however, no intention to change the attenuation rule. See Nardone v. United States, 127 F. 2d. 521 (2d), cert. denied, 316 U. S. 698 (1942); Wong Sun *559v. United States, 371 U. S. 471 (1963).” S. Rep. No. 1097, 90th Cong., 2d Sess., 96.
Thus, although the validity of a wiretap order depends on the satisfaction of certain statutory conditions in addition to the constitutional requirement of probable cause, the principle developed in Part I of this opinion is fully applicable to the November 6 wiretap extension order. The question is not whether the application for that order relied in part on communications intercepted under the invalid original order but whether, putting aside that tainted evidence, the independent and lawful information stated in the supporting affidavit suffices to show both probable cause and satisfaction of the various additional requirements of Title III.7 United States v. *560Iannelli, 339 F. Supp. 171 (WD Pa. 1972); United States v. Ceraso, 355 F. Supp. 126 (MD Pa. 1973).
The application for the wiretap éxtension order was supported by the affidavit of a group supervisor from the Bureau of Narcotics and Dangerous Drugs. The same officer had sworn to one of two affidavits submitted in support of the application for the original wiretap order. The other had been filed by a narcotics agent acting under his supervision and stated facts within their joint knowledge. In the affidavit for the extension order, the supervisor swore that he had reviewed both of the 'earlier affidavits, and he “reassert[ed] the facts, details and conclusions contained in those affidavits.” App. 66. Those allegations not only established probable cause to believe that Giordano was engaged in the illegal sale and distribution of narcotics on a fairly'substantial scale, 18 U. S. C. §2518 (3)(a), they also satisfied the additional statutory criteria for issuance of an intercept order. They showed, for example, that Giordano had made numerous telephone calls to numbers listed to well-known narcotics violators and hence that there was probable cause to believe that communications concerning the illegal drug traffic were taking place on Giordano’s telephone line. See 18 U. S. C. §§ 2518 (3)(b) and (d). The affidavits also established the inadequacy, of alternative investigative means and demonstrated tna.t, without a wiretap of Giordano’s telephone., the narcotics" agents would be unablq to discover his source of supply or method of distribution. See . 18 U. S. C. §2518 (3)(c). All this was shown on the basis of wholly untainted evidence incorporated and reaffirmed in the affidavit sup*561porting the Government’s request for the. wiretap extension order.
The affidavit also provided additional untainted information to support the application for the extension order. It set forth, for example, the circumstances of Giordano’s sale of $3,800 worth of heroin to an undercover agent on the day following issuance of the original wiretap order. Moreover, it recounted in great detail highly suspicious conduct observed by federal agents keeping Giordano under physical surveillance.8 Like the allegations incorporated by reference from the earlier affidavits, this additional untainted information was relevant both to the constitutional requirement of probable cause and to the various statutory criteria for issuance of an intercept order. 18 U. S. C. § 2518 (3).
In light of the substantiality and. detail of the untainted allegations offered in support of the application for the wiretap extension order, I find no basis for the majority’s rather summary conclusion that the communications intercepted under that extension order were derivatively tainted by the improper authorization of the application for the original wiretap order. Because neither the District Court nor the Court of Appeals has considered this question, I would remand the case with instructions that the issue be settled in accord with the principles set forth in this opinion.
A pen register is a mechanical device attached to a given telephone line and usually installed at a central telephone facility. It records on a paper tape all numbers dialed from that line. It does, not identify the telephone numbers from which incoming calls originated, nor does it reveal whether any call, either incoming or outgoing, was completed. Its use does not involve any monitoring of telephone conversations. The mechanical complexities of a pen register are explicated in the opinion of the District Court. 340 F. Supp. 1033, 1038-7-1041 (Md. 1972).
Under 18 U. S. C. §2518(3), the court is required to make the following determinations: '
“(a) there is probable cause for belief that an individual is committing, has committed, or is ‘about to commit a particular offense enumerated in section 2516 of this chapter; '
“ (b) .there is probable cause for belief that particular conmmnications concerning that offense will be ' obtained through such interception;
“(c) normal investigative procedures have been tried and have failed, or reasonably appear to be unlikely to succeed if tried or to be too dangerous,^
“(d) there is probable cause for belief that the facilities from which, or the place where, the wire .or oral communications are to be intercepted are being used, or are about to be used, in connection with the commission of such, offense, or are leased to, listed in the name of, or commonly used by such person.”
Immediately after stating its conclusion that the misidentification problem required suppression, the District Court made its sole reference to the November 6 extension order:
“The application and order relating to the extension of the wire*552tap are defective for the same reasons as the original application and order.” 340 F. Supp., at 1060.
Plainly, this reference to the “same reasons” concerns the failure to comply literally with §§2518(1) (a) and (4) (d) identification requirement: and- -has nothing to do with any derivative-evidence rule.
The Government suggests that the use of a pen register reay not constitute a search within the meaning of the Fourth'.Amendment. I need not address this question, for in my view the. constitutional guarantee, assuming its applicability, was satisfied in this case.
All of the cases' cited are directly on point. There are a few additional decisions that indirectly support the general proposition stated above. United States v. Cantor, 470 F. 2d 890 (CA3 1972), involved a defendant’s claim that the Government violated his Fourth Amendment rights .by refusing to disclose to him certain evidence that had been used to establish probable cause for issuance of a warrant. The court rejected that claim on the ground'that there-was adequate independent justification to find probable cause. Id., at 893. The cases of United States v. Jones, 475 F. 2d 723 (CA5 1973), and United States v. Upshaw, 448 F. 2d 1218 (CA5 1971), stand for the proposition that the validity of a search warrant based in part on erroneous statements is determined by evaluating the sufficiency of the other allegations. Finally, United States v. Lucarz, 430 F. 2d 1051 (CA9 1970), involved a search warrant based on an affidavit containing two paragraphs that invited the magistrate to find probable cause by drawing a negative inference from the defendant’s exercise of his constitutional right, to the assistance of counsel. The court held the validity of the warrant was to be determined on the básis of the other allegations in the affidavit.
In fact, there are only two cases lending even colorable-support to a contrary view. Both are from the Sixth Circuit, and neither can be said to contradict the general proposition stated above. In United States v. Langley, 466 F. 2d 27 (1972), the court considered the validity of a warrant issued on the basis of information obtained in a previous warrantless search. The court held the prior search valid in large part and affirmed the validity of the warrant for the second search despite the inclusion in the affidavit of allegations based on the unlawful aspects of the first search.. Although the case therefore illustrates the principle stated above, the court added the following comment: “It must be emphasized that where such tainted information comprises more than a very minor portion of that found in an affidavit supporting a warrant to search, the warrant must be held invalid.” Id., at 35 (emphasis in original).' The other case is United States v. Nelson, 459 F. 2d 884 (1972), where the affidavit for a search warrant relied on information derived from two prior warrantless searches.' Although the court suggested several reasons for suppressing the evidence seized pursuant to .the'warrant, the principal basis seems' to have been the finding that the untainted allegations did not' constitute probable cause.- Thus neither case contradicts the decisions of the District of Columbia, Third, Fifth, Eighth, and Ninth Circuits' cited in the text.
The majority" seems to believe that this principle, while fully applicable to original wiretap orders, is wholly inapplicable to extension orders. This, at least, is the most reasonable construction of the majority’s discussion of §§ 2518 (1) (e) and (f). Ante, at 532-533. Those provisions require that an application for an extension order include “a full and complete statement of the facts concerning all previous applications” and “a statement setting forth the results thus far obtained from the interception ...” According to the majority, the fact that law enforcement authorities complied with §§ 2518 (i) (e) and (f) by including in the application for the extension order information regarding the earlier wiretap necessarily and automatically rendered the extension order invalid, regardless of whether the independent and untainted information in ihe application for the extension satisfied the requirements of the Fourth Amendment and §2518 (3).
With all respect, I find this a baffling interpretation of the statute. Certainly there is nothing in the language or history of §§ 2518 (1) (e) and (f) to suggest that Congress intended these provisions to except all extension orders from the independent-source doctrine. Nor is there any suggestion in the language or history of § 2515, which is the statutory analogue .to the constitutional doctrine of the fruit of the poisonous tree, that Congress intended to distinguish between original wiretap orders and extension orders in determining the extent of the suppression remedy. Finally, there is nothing in logic *560to indicate why Congress would have wanted to make such a distinction, and there is no basis in reason to suppose that Congress, if it had intended such a’result, would have failed to leave any evidence of that intent.
The detailed information lawfully obtained through surveillance and undercover work was aptly summarized in ¶ 77 of the affidavit supporting, the extension order:
“Giordano "exhibits the characteristics of a high-level narcotics trafficker — extreme caution. When travelling, he continually uses various counter-surveillance, techniques. In his transactions, he limits his contacts to a.'small -number of trusted individuals.” App. 81.