concurring in the result:
The facts of this case give new meaning to the term “invasion” of privacy. Dressed in military camouflage uniforms, 24 to 30 officers of the Vermont State Police moved onto a 70-acre tract of private property in Sharon, Vermont, leased by one of the appellants as his residence, and, working in eight-hour shifts, maintained 24-hour surveillance of the appellants for three weeks. Observations were made of the appellants while inside and outside a house on the property. The observations were so continuous as to include viewings of some of the appellants using a toilet. Among the devices used to enhance the officers’ observations were field binoculars with 12-power magnification, a Bushness spotting scope with 45-power magnification, and a Questar lens with 130-power magnification. Some use was made of a Javelin nightscope, capable of magnifying existing light 50,000 times. The officers used infrared night goggles to facilitate their movement in the dark and concealed their presence not only by using the natural cover of trees and shrubs but also by cutting branches and brush to form a blind.
Without doubt there was an invasion. The Court suggests, however, that what was invaded by the exterior observations was not privacy,1 at least not the reasonable expectation of privacy protected by the Fourth Amendment. Fortunately that suggestion is dictum, since the majority holds that, wholly apart from the results of the para-military surveillance at Sharon, the independent information in an affidavit presented to the state judge who issued the search warrant adequately established probable cause for the search of the premises. I agree with that holding and therefore concur in the result, but I write separately to register respectful disagreement with the majority’s dictum, approving the exterior surveillance at Sharon, in the hope that this dictum will not in future cases ripen into a holding.
The majority’s endorsement of the Sharon surveillance purports to draw support from two doctrines, each illustrated by a number of cases cited in Judge Van Graaf-eiland’s opinion. The first is the “open fields” doctrine, which traces its Fourth Amendment lineage to Hester v. United *54States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898 (1924). The second is essentially a doctrine of waiver of Fourth Amendment protection as to items or activities willingly exposed to public view. In my judgment neither doctrine justifies the surveillance carried out in this case, nor do any of the cited cases remotely countenance what occurred here.
1. Both before and after Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967), shifted the appropriate inquiry in Fourth Amendment cases from places to people, or, more precisely, to a person’s reasonable or “legitimate” expectation of privacy, Rakas v. Illinois, 439 U.S. 128, 143 n.12, 99 S.Ct. 421, 430 n.12, 58 L.Ed.2d 387 (1978), the “open fields” doctrine had been invoked to uphold police activity in a context totally different from the circumstances of this case. Police have been permitted to intrude upon open areas of privately owned property on a brief, one-time basis to make specific observations of items or events that were either observable from beyond the property2 or about which the officers had prior information.3 None of the cases cited by Judge Van Graafeiland,4 nor any that I have located,5 invokes the “open fields” doctrine to validate an open-ended, long-term surveillance conducted on private residential property in the hope of seeing evidence of crime.
The distinction between all the prior cases and this one goes to the heart of the Fourth Amendment’s protection. The Amendment protects against “unreasonable” searches. Katz teaches that warrant-less searches are unreasonable if they intrude upon a person’s reasonable expectation of privacy. When a law enforcement officer sees smoke pouring from a factory chimney and steps onto an open area of the owner’s property to make a more precise observation, Air Pollution Variance Board v. Western Alfalfa Corp., 416 U.S. 861, 94 S.Ct. 2114, 40 L.Ed.2d 607 (1974), or when an officer receives information that a cache of dynamite is hidden in a junked car in an open field and goes to look, United States v. Ramapuram, 632 F.2d 1149 (4th Cir. 1980), cert. denied, 450 U.S. 1030, 101 S.Ct. 1739, 68 L.Ed.2d 225 (1981), his action is not “unreasonable”; it can fairly be said that he does not encroach upon an expectation of privacy that “society is prepared to recognize as ‘reasonable.’ ” Katz v. United States, supra, 389 U.S. at 361, 88 S.Ct. at 516 (Harlan, J., concurring). But when police officers execute military maneuvers on residential property for three weeks of round-the-clock surveillance, can that be called “reasonable”? Can it be doubted that society is prepared to recognize as “reasonable” the expectation of the tenant and his guests that the property will not be *55invaded for such purposes? I should think that even those in our society not overly fond of the Fourth Amendment and its implementing exclusionary rule would agree that every person may enjoy the privacy of his back yard secure in the belief that police officers are not bivouacked on his property just beyond the nearest tree line observing him with high-powered telescopes day and night for three weeks.
The “open fields” of private property are not open for any surveillance police officers choose to conduct, unrestricted as to duration, constancy of observation, location observed, or means of enhanced viewing. The narrow holding of Hester supports no such rule. Officers there approached the residence of an individual about whom they had prior information. When they saw another man drive up to the house, they concealed themselves and maintained observation only long enough to see the immediate episode at hand, the transfer of a quart of moonshine whiskey. Dealing with the contention that the officers’ subsequent examination of a bottle and jug dropped on the ground violated the Fourth Amendment, Justice Holmes said that the “special protection accorded by the Fourth Amendment to the people in their ‘persons, houses, papers, and effects,’ is not extended to the open fields. The distinction between the latter and the house is as old as the common law.” 265 U.S. at 59, 44 S.Ct. at 446. If that observation was intended to mean that no Fourth Amendment protection extends beyond the house, its validity has not survived either the holding or the rationale of Katz, which extended Fourth Amendment protection to a person using a public telephone because the person was entitled to enjoy a legitimate expectation of privacy. See United States v. Mullinex, 508 F.Supp. 512, 514 (E.D.Ky.1980) (“The final analysis [after considering the impact of Katz upon Hester ] is that ‘open fields’ are not per se outside the protective boundary of the Fourth Amendment, but a defendant’s expectation of privacy in an open field must be an expectation that society would consider as reasonable.”) (emphasis in original).
Courts have not had to consider whether police officers may occupy a property owner’s open fields for prolonged and continuous surveillance of his back yard because, until today, it does not appear that police officers have asserted such authority. But many courts that have upheld surveillance conducted on, over, or from open fields have been careful to note the limited extent of the surveillance and to caution against unrestricted surveillance. United States v. DeBacker, 493 F.Supp. 1078 (W.D.Mich. 1980) (aerial surveillance of private property upheld because only isolated instances occurred); State v. Stachler, 58 Hawaii 412, 570 P.2d 1323 (1977) (same). See United States v. Jackson, 588 F.2d 1046, 1053 n.12 (5th Cir.) (“[T]his court may, under different facts, find a Fourth Amendment violation even though the government agents make their observations from an ‘open field’ ”), cert. denied, 442 U.S. 941, 99 S.Ct. 2882, 61 L.Ed.2d 310 (1979); United States v. Brown, 487 F.2d 208, 210 (4th Cir. 1973) (observing, even as to one-time appearance on property, “It is a bit disquieting that we must countenance federal snooping around farmers’ barns as a legitimate investigative technique”), cert. denied, 416 U.S. 909, 94 S.Ct. 1617, 40 L.Ed.2d 114 (1974); Fullbright v. United States, 392 F.2d 432, 435 (10th Cir.) (“[W]e do not mean to say that surveillance from outside a curtilage under no circumstances could constitute an illegal search.... ”), cert. denied, 393 U.S. 830, 89 S.Ct. 97, 21 L.Ed.2d 101 (1968). As Judge Hillman observed in United States v. DeBacker, supra, 493 F.Supp. at 1081, “The ultimate question, therefore, is not whether the surveillance in this case occurred in ‘open fields’. Instead, the issue is whether ‘if the particular form of surveillance practiced by the police is permitted to go unregulated by constitutional restraints, the amount of privacy and freedom remaining to citizens would be diminished to a compass inconsistent with the aims of a free and open society.’ ” (quoting Amersterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 403 (1974) (emphasis added)).
*56Moreover, even apart from the particular form of the surveillance, “absent exigent circumstances a warrantless search of one’s home or its curtilage, when effected through trespass, violates the fourth amendment.” United States v. Van Dyke, 643 F.2d 992, 993 (4th Cir. 1981). As Judge Friendly has pointed out, “Terming a particular area curtilage expresses a conclusion; it does not advance Fourth Amendment analysis. The relevant question is . . . whether the defendant has a legitimate expectation of privacy in the area.” United States v. Arboleda, 633 F.2d 985, 992 (2d Cir. 1980), cert. denied, 450 U.S. 917, 101 S.Ct. 1362, 67 L.Ed.2d 343 (1981). But obviously the nature of the area observed, its proximity to one’s home, the extent of surrounding trees and shrubs, and the general setting of the area within the larger context of the total property are all relevant in assessing the reasonableness of an expectation of privacy. These defendants, while in the immediate area of the home one of them had rented on a 70-acre farm in rural Vermont, had a reasonable expectation of privacy that they would not be observed by highly intrusive surveillance conducted upon the open fields of the leased property.
2. I have no quarrel with the majority’s general statement of its second proposition, “What was observable by the general public was observable without a warrant by the police as well.” That statement, paraphrasing a sentence in Marshall v. Barlow’s, Inc., 436 U.S. 307, 315, 98 S.Ct. 1816, 1821, 56 L.Ed.2d 305 (1978), derives from the following sentence in Katz v. United States, supra, 389 U.S. at 351, 88 S.Ct. at 511: “What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection.” Before endeavoring to apply that statement, it is well to identify its origins. The supporting citations in Katz are Lewis v. United States, 385 U.S. 206, 210, 87 S.Ct. 424, 427, 17 L.Ed.2d 312 (1966), and United States v. Lee, 274 U.S. 559, 563, 47 S.Ct. 746, 748, 71 L.Ed. 1202 (1927). Lewis concerns observations made by an undercover agent invited into the defendant’s home to purchase narcotics. The case involves misplaced confidence and does not illuminate the Katz-Marshall principle of public exposure, since nothing was viewed or viewable by the public. Lee concerns a view of items on the deck of a motor boat on the high seas by agents on a Coast Guard vessel. The case is more pertinent to a principle of public exposure because the items were located where any member of the public, at least any sea-going member, could see them, and the observation made by law enforcement officers was precisely the one that the defendant could have reasonably expected.
Katz itself supplies some content to the principle of “public exposure” by holding that even in an area accessible to the public, what a person seeks to preserve as private may be constitutionally protected. 389 U.S. at 351-52, 88 S.Ct. at 511-12. Marshall v. Barlow’s, Inc., supra, adds an important qualification by making clear that exposure to some limited segment of the public, there employees, is not the sort of public exposure that removes Fourth Amendment protection against government observations. See also Mancusi v. DeForte, 392 U.S. 364, 369, 88 S.Ct. 2120, 2124, 20 L.Ed.2d 1154 (1968) (defendant who shared an office entitled to Fourth Amendment protection for its contents, even though he could expect that contents would be observed by those who shared the office and by their business and personal guests).
In suggesting, albeit in dictum, that the exterior surveillance at Sharon impaired no Fourth Amendment right of the defendants because the area viewed was exposed to the public, the majority has extended the public exposure doctrine in two significant respects beyond the holdings of other courts. The first extension concerns who could have made the observations; the second concerns the location from which they could have been made.
Though the District Court stated that “outsiders” could enter the Sharon property “at will,” 502 F.Supp. at 1038, Judge Holden’s specific factual findings make clear that he is not referring to the public at large but only to a narrow segment. The *57owners (two couples) retained the right to use the property for recreational purposes, neighbors had permission to use the pond, and hunters could hunt on the property. Id. at 1026-27. Since it is undisputed that the surveillance occurred out of the hunting season, the “outsiders” whose observations the defendants risked were the owners and neighbors when using the pond. No doubt defendants did bear the risk that an owner or neighbor might observe unlawful activity and report it to the police, just as the defendant bore the risk in Marshall v. Barlow’s, Inc., supra, that employees would report OSHA violations to Government inspectors. 436 U.S. at 315, 98 S.Ct. at 1821. But risking observation by a limited category of persons is not the equivalent of public exposure and does not displace a reasonable expectation of privacy against “governmental intrusion.” Mancusi v. DeForte, supra, 392 U.S. at 368, 88 S.Ct. at 2123.
As to the location from which the back yard at Sharon was observable, it could be seen from a point on what Judge Holden called an “unimproved town road,” 502 F.Supp. at 1026. But it is undisputed that the surveillance was not made from this point. The majority cites no case where the risk of being observed from one spot accessible to the public has been considered the sort of public exposure that relinquishes a reasonable expectation of privacy that surreptitious observations will not be made from locations on private property. In fact, all of the cases cited by the majority that uphold police observations on a “public exposure” theory involve sightings made from precisely the location from which the defendant knew or should have known he was observable.
Perhaps cases may arise where a person is observable from several locations accessible to the public and may thereby be deemed to have exposed himself to the public so as to lose any reasonable expectation of privacy against government observation, even from some other location.6 But surely that situation is not reached by people in the back yard of a rural Vermont farm property, simply because observation was physically possible from one point on a rarely used road. A person in a back yard reading Karl Marx or sunbathing in the nude is entitled to rely on his or her own sense of whether anyone is at the one point on an adjacent road from which observation is possible. They take the risk of not hearing a car or otherwise not realizing that someone is there, but that slight risk does not expose them to three weeks of 24-hour surveillance by camouflaged police officers peering through telescopes from concealed positions on their property.
To summarize, the exterior surveillance of the defendants in the area of the house at the Sharon property, though conducted from an “open field” of the property, violated the defendants’ reasonable expectation of privacy because of the offensively intrusive manner in which police officers operated on the property, and that reasonable expectation of privacy was not displaced by the possibility that a few identifiable people might have observed the defendants from locations on the property or that anyone might have observed them from one point on a little-used, unimproved road. I regret that the majority, even in dictum, has expressed approval of what occurred in this case. Since the surveillance I regard as unlawful was not essential to the validity of any of the challenged searches and seizures, I concur in the result.7
. The results of the interior observations were suppressed by the District Court, 502 F.Supp. 1021, 1040-41, and the correctness of that ruling is not in issue on this appeal.
. E.g., Air Pollution Variance Bd. v. Western Alfalfa Corp., 416 U.S. 861, 94 S.Ct. 2114, 40 L.Ed.2d 607 (1974); United States v. Varkonyi, 645 F.2d 453 (5th Cir. 1981); United States v. Freie, 545 F.2d 1217 (9th Cir. 1976), cert. denied, 430 U.S. 966, 97 S.Ct. 1645, 52 L.Ed.2d 356 (1977).
. E.g., United States v. Ramapuram, 632 F.2d 1149 (4th Cir. 1980), cert. denied, 450 U.S. 1030, 101 S.Ct. 1739, 68 L.Ed.2d 225 (1981); United States v. Minton, 488 F.2d 37 (4th Cir. 1973), cert. denied, 416 U.S. 936, 94 S.Ct. 1936, 40 L.Ed.2d 287 (1974); Fullbright v. United States, 392 F.2d 432 (10th Cir.), cert. denied, 393 U.S. 830, 89 S.Ct. 97, 21 L.Ed.2d 101 (1968).
. Of all the cases cited in the majority’s opinion, the only one involving any long-term, surreptitious surveillance is United States v. Hensel, 509 F.Supp. 1376 (D.Me.1981). In Hensel the surveillance was conducted from locations off the defendant’s property, although some instances of aerial surveillance occurred. The degree of intrusiveness is reflected in the fact that the surveillance could not even identify any of the individuals observed. The one-time physical entry into the driveway resulted in observation only of a license plate number, as to which defendant had no reasonable expectation of privacy. Id. at 1386.
. McDowell v. United States, 383 F.2d 599 (8th Cir. 1967), approved surveillance conducted on the open fields of private property, but the case is readily distinguishable from what happened here. In McDowell initial surveillance of fields suspected of being used for illegal hunting of migratory birds was conducted from locations off the defendant’s property. When alerted by unusual activities in the fields, agents entered the fields on three occasions for a closer look. Their observations were confined to open areas, one-quarter to one-half a mile from the nearest farm building.
. Even that circumstance would not necessarily validate an observation made from a location on the defendant’s property.
. While I do not share the majority’s concern that defendants’ briefs omit the word “innocent,” since their guilty pleas with a reservation of appellate rights usefully saved considerable time and expense, some comment on the plea procedure is warranted. The practice of pleading guilty with a reservation of right to appeal a pre-trial ruling has been used in the context of a single pre-trial issue that all sides recognized would be dispositive of the entire case. See, e.g., United States v. Faruolo, 506 F.2d 490, 491 n.2 (2d Cir. 1974) (voluntariness of consent to search); United States v. Rothberg, 480 F.2d 534, 535 & n.1 (2d Cir.) (construction of statute defining offense), cert. denied, 414 U.S. 856, 94 S.Ct. 159, 38 L.Ed.2d 106 (1973); United States v. Mann, 451 F.2d 346, 347 (2d Cir. 1971) (pre-trial delay). The prac*58tice was suggested to our Circuit by Judge Friendly in United States v. Doyle, 348 F.2d 715, 719 (2d Cir.), cert. denied, 382 U.S. 843, 86 S.Ct. 89, 15 L.Ed.2d 84 (1965), though previously used elsewhere, e.g., Jaben v. United States, 333 F.2d 535 (8th Cir. 1964), aff’d without consideration of the point, 381 U.S. 214, 85 S.Ct. 1365, 14 L.Ed.2d 345 (1965). But see United States v. Mizell, 488 F.2d 97 (5th Cir. 1973) (rejecting the practice).
The use of the practice in this case to preserve for appellate review a considerable number of issues is potentially troublesome. Suppose, for example, we had found one of the several challenged seizuies unlawful. Under the terms of the defendants’ plea agreements, it would certainly be arguable that upon a determination that even one seizure was unlawful, the defendants could withdraw their guilty pleas. Yet if the lawfulness of the seizures had not been adjudicated until after a trial, the unlawfulness of any one seizure might well have been found to be harmless error, in light of the weight of the admissible evidence. Pleading guilty with a reservation of appellate rights should not be a device to circumvent the harmless error rule. The problem does not arise in this case since we affirm the results of all of the pre-trial rulings. But it is a problem to which the Government and District Judges should be alert in accepting conditional guilty pleas hereafter. When multiple pre-trial rulings concerning evidence are to be challenged, one solution would be for the parties to stipulate, for purposes of the conditional guilty plea, to an agreed statement of the admissible evidence apart from the challenged rulings, with withdrawal of the plea permitted only upon an appellate determination that a pre-trial ruling was not only erroneous but prejudicial in light of the stipulated evidence.