JUSTICE KIRSHBAUM delivered the Opinion of the Court.

The petitioners, Robin Hoffman and Larry Hoffman (Hoffmans), were convicted in separate trials in Morgan County District Court of cultivation of marijuana, in violation of section 18-18-106(8)(a)(I), 8B C.R.S.(1986). They appealed, and the Court of Appeals affirmed their convictions. Having granted certiorari to review issues relating to the trial court's order denying the Hoffmans' motion to suppress evidence, we reverse and remand with directions.

I

On July 20, 1985, Robert Aufenkamp, then Chief of Police of Log Lane Village, received a telephone call from an anonymous citizen indicating that marijuana might be growing in the backyard of a residence located in that community. He and Lieutenant Dana Speaks of the Morgan County Sheriff's Department drove to the residence. Speaks knocked on the front door of the residence. Receiving no answer, he and Aufenkamp drove to the back of the residence and stopped in a service alley abutting the Hoffmans' backyard. From one vantage point they observed a garden through a wire mesh fence enclosing the backyard. Among the vegetables and flowers growing in the garden were what the officers believed to be marijuana plants. Speaks took photographs of the plants from the alley.

The two officers then opened an unlocked gate in the fence and entered the backyard. When Speaks received no response to his knock on the back door of the residence, he and Aufenkamp walked to the garden, took additional pictures of the plants, removed them and took them to an evidence room at the Morgan County sheriff's office. Subsequent testing confirmed that the plants were marijuana plants.

Prior to his trial, Larry Hoffman filed a motion to suppress introduction of the marijuana plants into evidence on the ground that in the absence of a warrant the officers' conduct was constitutionally impermissible. He and Robin Hoffman, who later joined in the motion, argued that while the off-premises sighting of the marijuana was lawful, the entry into the backyard and particularly the seizure of the plants violated their rights to privacy in their residence and its curtilage.

At the suppression hearing the People acknowledged the absence of any search warrant supporting the seizure of the plants and presented testimony by the two police officers to justify the seizure. The People argued that because the backyard and its contents were fully visible to the officers and anyone else from the public alley, the Hoffmans had no legitimate expectation of privacy in the garden area of their backyard and that in any event the officers were justified in entering the yard and seizing the plants.

The trial court denied the suppression motion. The trial court's order contained the following pertinent language:

"I have difficulty in this case accepting the proposition that the defendant had any — or defendants had any expectation or reasonable expectation of privacy where the fence as I gather was transparent, that is to say, it was a wire fence, was a situation where you had a garden that was readily visible at least from an alley and, at least according to the evidence received, from a public highway.

"It seems under those circumstances there is no expectation of privacy as to the items that can be observed. If there is no expectation of privacy, I frankly don't see that there is any violation, constitutional violation of such gravity that it requires the suppression of evidence in this case."

Robin Hoffman was convicted by a jury of the offense of cultivation of marijuana and sentenced to two years' probation. Larry Hoffman was convicted of the same offense following a trial to the court and was sentenced to three years' probation. On appeal, the Court of Appeals affirmed the judgments in a one-page opinion, stating:

"[W]e conclude that the trial court rulings were correct for the reasons assigned by the People in the answer briefs. We regard the following cases to be dispositive of the arguments and issues raised. People v. Shorty, 731 P.2d 679 (Colo. 1987); People v. Gomez, 632 P.2d 586 (Colo. 1981); People v. Ortega, 175 Colo. 136, 485 P.2d 894 (1971)." People v. Hoffman and Hoffman, Nos. 86CA0647 and 86CA1198, slip op. at 1 (Colo.Ct.App. Sept. 17, 1987).

II A

The fourth amendment to the United States Constitution and article II, section 7, of the Colorado Constitution protect persons from unreasonable searches and seizures. See Ker v. California, 374 U.S. 23 (1963); Mapp v. Ohio, 367 U.S. 643 (1961). Searches have been described as intrusive governmental investigations or explorations into non-public places for that which is concealed. See W. LaFave, Search and Seizure § 2.1(a), 301-03 (2d ed. 1987). However, the mere observation by government officials of that which is plainly visible to anyone does not constitute a search for constitutional purposes. See California v. Ciraolo, 476 U.S. 207 (1986); Fagundes v. United States, 340 F.2d 673 (1st Cir. 1965); People v. Becker, 188 Colo. 160, 533 P.2d 494 (1975). Seizures, on the other hand, refer to some meaningful interference with an individual's possessory interest in personal property such as the physical taking and removing of such property. United States v. Jacobsen, 466 U.S. 109, 113 (1984); W. LaFave, Search and Seizure § 2.1(a), 299-301 (2d ed. 1987).

The touchstone of fourth amendment analysis is whether a person has a "constitutionally protected reasonable expectation of privacy" in the area or item searched or seized. U.S. v. Katz, 389 U.S. 347, 360 (1967) (Harlan, J., concurring). See Ciraolo, 476 U.S. at 211; Oliver v. United States, 466 U.S. 170, 177 (1984). That determination requires the court to ascertain whether an individual has exhibited a subjective expectation of privacy in the particular place or object in question and whether that subjective expectation is one society recognizes as reasonable. Katz, 389 U.S. at 361. The existence of a legitimate expectation of privacy must be determined after examining all the facts and circumstances in each particular case. Oliver, 466 U.S. at 177-78; People v. Shorty, 731 P.2d 679, 681 (Colo. 1987); People v. Oates, 698 P.2d 811, 819 (Colo. 1985); People v. Savage, 630 P.2d 1070, 1073 (Colo. 1981).

In the present case, the Hoffmans and the People agree that the officers' off-site observation of the marijuana plants did not constitute a search for fourth amendment purposes. There is no invasion of privacy in the observation of that which is plainly visible to the public. See Fagundes, 340 F.2d 673 (1st Cir. 1965); Petteway v. United States, 261 F.2d 53 (4th Cir. 1958). As the Supreme Court has recognized, "[w]hat a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection." Katz, 389 U.S. at 351. Thus, in general, a curtilage is not protected from observations that are lawfully made from outside its perimeter not involving physical intrusion. Florida v. Riley, 109 S. Ct. 693, 696 (1989); Ciraolo, 476 U.S. at 213.

B

The fact that the officers legitimately obtained sufficient information to establish probable cause to believe the Hoffmans had committed an offense does not end the inquiry. Probable cause permits officers to obtain a warrant to search premises and to seize property. See Specht v. Jensen, 832 F.2d 1516 (10th Cir. 1987), cert. denied, 109 S. Ct. 792 (1989); U.S. v. Burns, 624 F.2d 95 (10th Cir.), cert. denied, 449 U.S. 954 (1980); People v. Rayford, 725 P.2d 1142 (Colo. 1986); People v. Hill, 690 P.2d 856 (Colo. 1984). The officers here elected to enter the backyard, walk to the garden and seize the marijuana plants, all without first obtaining a warrant judicially authorizing such conduct.

Warrantless searches and seizures are presumptively invalid under the fourth amendment to the United States Constitution and article II, section 7, of the Colorado Constitution, subject only to a few specifically delineated exceptions. See Thompson v. Louisiana, 469 U.S. 17 (1984) (per curiam); United States v. United States Dist. Court, 407 U.S. 297 (1972); People v. Dandrea, 736 P.2d 1211 (Colo. 1987); People v. Reynolds, 672 P.2d 529 (Colo. 1983); People v. Stoppel, 637 P.2d 384 (Colo. 1981). The prosecution bears the burden of establishing that warrantless conduct by government officials falls within one of those exceptions. See Arkansas v. Sanders, 442 U.S. 753 (1979); Mincey v. Arizona, 437 U.S. 385 (1978); People v. Jansen, 713 P.2d 907 (Colo. 1986); People v. Turner, 660 P.2d 1284 (Colo. 1983); People v. Williams, 200 Colo. 187, 613 P.2d 879 (1980).

While the fourth amendment protects people rather than places, Katz, 389 U.S. at 353, particular places retain significance for purposes of determining the scope of fourth amendment protections. Certain areas, such as the interiors of homes and offices, are deemed to be constitutionally protected areas. See Mincey, 437 U.S. at 391; People v. Turner, 660 P.2d 1284, 1287 (Colo. 1983). The United States Supreme Court recognized this distinction in Coolidge v. New Hampshire, 403 U.S. 443, 468 (1971), in the following language:

"[P]lain view alone is never enough to justify the warrantless seizure of evidence. This is simply a corollary of the familiar principle . . . that no amount of probable cause can justify a warrantless search or seizure absent "exigent circumstances." Incontrovertible testimony of the senses that an incriminating object is on premises belonging to a criminal suspect may establish the fullest possible measure of probable cause. But even where the object is contraband, this Court has repeatedly stated and enforced the basic rule that the police may not enter and make a warrantless seizure. See also Illinois v. Andrews, 463 U.S. 765 (1983).

One area traditionally recognized as deserving of special protection from unwarranted government intrusion is the area immediately surrounding a private residence, or the curtilage. As the United States Supreme Court stated in Dow Chemical Co. v. United States, 476 U.S. 227, 235 (1986), "[t]he curtilage area immediately surrounding a private house has long been given protection as a place where the occupants have a reasonable and legitimate expectation of privacy that society is prepared to accept." Courts have recognized that this area is entitled to the same level of protection as is a residential dwelling because it harbors the "intimate activity associated with the `sanctity of a [person's] home and the privacies of life.'" Boyd v. United States, 116 U.S. 616, 630 (1886). The Supreme Court has identified four factors to consider in defining the extent of a home's curtilage: "the proximity of the area claimed to be curtilage to the home, whether the area is included within an enclosure surrounding the home, the nature of the uses to which the area is put, and the steps taken by the resident to protect the area from observation by people passing by." United States v. Dunn, 480 U.S. 294, 301 (1987). Although we stated in People v. Becker, 188 Colo. 160, 163, 533 P.2d 494, 496 (1975), that "[t]he curtilage concept, properly understood, merely restates what the Supreme Court expressed in Katz as to a reasonable expectation of privacy," the concept of curtilage continues to play an independent role in fourth amendment analysis. See Dunn, 480 U.S. at 300; Ciraolo, 476 U.S. at 212-13; Oliver, 466 U.S. at 180.

The initial question raised by the Hoffmans' motion is whether the marijuana plants were located outside the curtilage of their house. If so, the Hoffmans in all probability could not establish either prong of the Katz test and, therefore, could assert no constitutionally protected privacy interest. Moreover, if the plants were located within the curtilage, but the curtilage was determined to have been generally accessible by as well as visible to the general public, a Katz analysis might reveal that the Hoffmans either had no subjective expectation of privacy in the curtilage or, if so, that their subjective expectation of privacy is not one acceptable to society. See Ciraolo, 476 U.S. at 213; United States v. Smith, 783 F.2d 648, 651 (6th Cir. 1986); United States v. Magana, 512 F.2d 1169, 1170 (9th Cir.), cert. denied, 423 U.S. 826 (1975); Shorty, 731 P.2d at 681.

The trial court erroneously assumed that the fact that the plants were visible from one point in the alley foreclosed any assertion of reasonable expectations of privacy by the Hoffmans. Its order does not contain findings as to whether the plants were located in the curtilage and, if so, whether under all relevant circumstances the Hoffmans had no reasonable expectations of privacy in their garden. See State v. Rickard, 420 So.2d 303 (Fla. 1982); State v. Rowe, 422 So.2d 75 (Fla.Dist.Ct.App. 1982); State v. Hook, 60 Haw. 197, 587 P.2d 1224 (1978); People v. Pakula, 89 Ill. App.3d 789, 411 N.E.2d 1385 (Ill.App. 1980); State v. Silva, 509 A.2d 659 (Me. 1986); State v. Prier, 725 S.W.2d 667 (Tenn. 1987). But see People v. Schmidt, 168 Ill. App.3d 873, 522 N.E.2d 1317 (1988); State v. Loomis, 436 So.2d 1103 (Fla.Dist.Ct.App. 1983); State v. McConnell, 422 So.2d 74 (Fla.Dist.Ct.App. 1982); Lightfoot v. State, 356 So.2d 331 (Fla.Dist.Ct.App.), cert. denied, 361 So.2d 833 (1978). The case must be remanded to the trial court for the entry of appropriate factual findings and the application of these principles. See Crim. P. 41(e).

C

The Court of Appeals cited three decisions of this court in affirming the trial court's ruling. However, in each of those cases special circumstances supported the conduct of police officials. In People v. Shorty, 731 P.2d 679 (Colo. 1987), we held that the defendant had no reasonable expectation of privacy in a common landing located outside the front door to his apartment which was accessible to anyone. We therefore found no fourth amendment violation when police officers lifted a piece of carpet located on the landing and seized a packet of cocaine hidden thereunder. In People v. Gomez, 632 P.2d 586 (Colo. 1981), cert. denied, 455 U.S. 943 (1982), we concluded that a warrantless entry and seizure of contraband was permissible under the doctrine of exigent circumstances because the defendants knew police officers were present and quick action was required to preserve evidence in a motel room observed through a window.

Finally, in People v. Ortega, 175 Colo. 136, 485 P.2d 894 (1971), police officers received information that the defendant was hiding narcotics in his backyard and set up a surveillance. The officers watched the defendant walk to a weeded area in his backyard, bend in a crouching position for a few seconds and then start to return to his residence. When the officers called out to him, he threw an object into the grass. The officers then arrested him, seized the packet he had discarded, and also seized LSD and marijuana from the weeded area he had just visited. We found no constitutional violation in this warrantless seizure of drugs from the defendant's backyard, holding that the packet had been abandoned by the defendant and the LSD and marijuana were seized incident to an arrest based upon probable cause. We also concluded that the officers' observations of defendant's conduct did not violate any fourth amendment privacy interest.

In each of these cases the defendant was present on the property and became aware that police officers were also present in a situation in which the officers' need to act quickly was amply demonstrated. Those circumstances are not present in this case. We therefore do not view those decisions as dispositive of the issues raised here.

III

In view of the foregoing discussion, it is clear that the trial court failed to make sufficient findings and apply the appropriate test to the Hoffmans' fourth amendment argument. However, the People argue that the entry and the seizure here was justified under the doctrine of exigent circumstances. See People v. Turner, 660 P.2d 1284, 1287-88 (Colo. 1983); People v. Hogan, 649 P.2d 326, 331 (Colo. 1982); McCall v. People, 623 P.2d 397, 402 (Colo. 1981). The People also argue that the Hoffmans' convictions should be affirmed pursuant to the doctrine of inevitable discovery. See, e.g., Murray v. United States, 108 S. Ct. 2529 (1988); Nix v. Williams, 467 U.S. 431 (1984); People v. Schoondermark, 759 P.2d 715 (Colo. 1988). Finally, the People contend that even if the trial court erred in admitting the marijuana plants into evidence, such constitutional error was harmless beyond a reasonable doubt. See Kotteakos v. United States, 328 U.S. 750, 764 (1946); Crespin v. People, 721 P.2d 688, 691 (Colo. 1986); Graham v. People, 705 P.2d 505, 509 (Colo. 1985); People v. Quintana, 665 P.2d 605, 612 (Colo. 1983).

The trial court did not consider the issues of exigent circumstances and inevitable discovery. It should be permitted to do so in the event it alters its initial decision on the Hoffmans' motion, particularly in view of the fact that additional factual findings might be required to resolve those issues. The issue of harmless error was not included among the issues accepted for certiorari review, and we elect not to address it.

IV

For the foregoing reasons, the judgment of the Court of Appeals is reversed. The case is remanded to the Court of Appeals with directions to remand to the trial court for the conduct of such further proceedings as the trial court may deem appropriate, to permit reconsideration of the Hoffmans' motion to suppress evidence, pursuant to the appropriate standards set forth in this opinion. In the event the trial court concludes that the suppression motion should be denied, the judgments of conviction will remain and the Hoffmans may appeal such ruling to the Court of Appeals. In the event the trial court grants the motion and therefore orders new trials for the Hoffmans, the People may appeal such ruling pursuant to C.A.R. 4.1.

JUSTICE ERICKSON dissents.

JUSTICE VOLLACK dissents, and JUSTICE ROVIRA joins in the dissent.