In criminal law the facts can be simple but the law complex. This is why criminal lawyers appear to some observers to be vastly more intelligent than their colleagues who practise in civil law.
The implied licence to enter private property can give rise to differences of judicial opinion on whether a police officer carried out a search and if so whether it was done lawfully.
In Florida v Jardines, USSC No 11-564 the Court split 5-4 on the lawfulness of a search where an officer had taken a drug dog on a lead to the front door of a house intending to knock and speak to the occupier. The officer was acting on information that drug offending was occurring on the property. The dog indicated the smell of drugs and the officer left the property with the dog and obtained a warrant to search the address. When the warrant was executed evidence of cannabis offending was found.
The opinion of the Court, delivered by Scalia J, was that the officer with the dog had carried out a search in breach of the implied licence to enter and knock. The main grounds for this decision were trespass, but in a concurring opinion Kagan J, joined by Ginsburg and Sotomayor JJ, the alternative ground of breach of privacy was advanced as an easier answer. The dissent was delivered by Alito J, joined by Roberts CJ, Kennedy and Breyer JJ.
The facts invite consideration of a variety of issues:
- What was the significance of the presence of the dog?
- Do the police have common law powers that ordinary members of the public do not?
- Should lawfulness here be determined by considerations of trespass or of privacy?
Alito J denied that the implied licence that qualifies trespass had ever been held to have prevented an officer bringing a dog onto the property. Obviously that point is not particularly significant because the law hasn't yet anticipated every possible occurrence. Absence of authority for a proposition is not authority against the proposition, although it can suggest that the conduct has previously been thought reasonable.
Alito J pointed out that the law has never attempted to distinguish categories of visitors as being welcome and therefore within the implied licence or unwelcome and therefore outside the licence. Any visitor with a lawful purpose may enter at a reasonable time of day and walk on the path that typically approaches the front door and, without lingering, knock on the door in an attempt to speak to an occupant. The police may do this too, and they do not search by simply approaching the door to knock and talk, even where the intention is to talk with a view to obtaining evidence against an occupier.
And if, continued Alito J, the officer in approaching the door with that intention, happened to smell evidence of drug offending, that information is not obtained outside the scope of the implied licence. So too for things seen and heard from a lawful vantage point. The officer is permitted to smell, hear and see what any person might detect on a lawful approach to the front door (citing State v Cada, 129 Idaho 224, at 232, 923 P. 2d 469 at 477).
Given that the officer could use his own nose, continued Alito J, what was wrong with him using the dog? There was no authority prohibiting the officer from having the dog with him, and indeed there has been no case in 800 years in which a tracking dog has been held to create a trespass. So, concluded the dissent, trespass is not a proper basis for holding the present conduct unlawful.
Nor, continued Alito J, could the occupiers have any reasonable expectation of privacy in relation to odours emanating from unlawful activities and reaching places where members of the public may lawfully stand. This is not the same as the use of new technology to enhance the sensing of information. It would hamper legitimate law enforcement activity if the dog's nose were to be equated with new technology.
However the dissent must now be regarded as incorrect in the jurisdictions in which Jardines applies. This is not to say that elsewhere the dissent's view of the law should not be accepted. Although the Court was concerned with constitutional interpretation, the origins of the law against unreasonable search and seizure are in the common law of England. While originating in the customs of England, the common law can develop differently according to social needs in different places. And a change in the common law brought about by decisions of the European Court of Human Rights in relation to judicial decisions made in Britain (for example as occurred in Malone v United Kingdom  ECHR 10, overturning Malone v Metropolitan Police Commissioner  Ch 344) does not necessarily affect the common law of another country. So although Jardines is not a "common law" decision in the narrow sense that the term "common law" is used in the United States, it is of interest wherever the meaning of search and the scope of police powers in relation to private property have to be decided.
The opinion of the Court in Jardines therefore is not binding but is "of interest" to courts outside the jurisdiction in which it applies. Scalia J, after deciding that the investigation took place in a constitutionally protected area, turned to consider whether the intrusion was authorised. Inevitably the relevant common law decision, known to the Founders and repeating an ancient custom of the realm, is Entick v Carrington, 2 Wils. K.B. 275, 95 ER 807 (K.B. 1765). As every lawyer knows, or once knew, this case reminds us that "our law holds the property of every man so sacred, that no man can set his foot upon his neighbour's close without his leave."
This rule, underlying the Fourth Amendment, raised the question whether a licence to enter could be implied in the circumstances of this case. Scalia J held that introducing a trained police dog to explore the area around the home was not customarily recognised as being within an implied licence to enter. The scope of the licence to enter and knock on the front door was limited both to a particular area and to a particular purpose. There was no invitation to the officer to enter and conduct a search. It was not the dog that was the problem, so much as the purpose of the entry. The common law would not licence a person who, remaining on the path to the door, used binoculars to peer through a window.
The Fourth Amendment has a property-based interpretation, supplemented in appropriate cases with a privacy based interpretation. Where a case can be decided on property-based grounds there is no need to add an inquiry about whether the defendant had a reasonable expectation of privacy. Here, reasoned Scalia J, the use of the dog and questions about privacy interests in respect of odours emanating from illegal activities on the property, were privacy issues and did not need to be considered because the case turned on property interests. The point was that the officer entered to conduct a search and that was outside the implied licence. Since there had been an unauthorised search, the Court upheld the Supreme Court of Florida's decision that the trial judge had correctly excluded the evidence obtained through entry with the dog and execution of the improperly obtained search warrant.
It is not inevitable that issues concerning searches have to be analysed in terms of first property rights, then if necessary, privacy rights. The reverse can also work, as is illustrated by the concurring opinion in Jardines, and, for an example from further afield, in Hamed v R  NZSC 101, at . Hamed also contains some controversial remarks from the Chief Justice about whether the police have common law powers that ordinary people do not have (she held that they don't), and although the other members of the Court did not directly address that point the Court of Appeal has subsequently decided – although in my view by a bit of a stretch - that Hamed is consistent with the view that the police do have additional common law powers: Lorigan v R  NZCA 264. The consequences of illegality may also differ between jurisdictions, and may be determined by legislation. The interpretation in Hamed of the relevant statute was discussed here on 19 September 2011. Some attempt has been made in New Zealand to codify the law of search: Search and Surveillance Act 2012. In circumstances like those in Jardines the relevant section would be s 20, but this does not specify the bounds of an implied licence. The consequences of a breach of an implied licence are left to be determined in the same way as before the Act (which is due to come fully into force by 1 April 2014, if not earlier by Order in Council). The position is summarised in Adams on Criminal Law – Rights and Powers, para SS20.05:
Where the constable's reasonable suspicion as to the commission of an offence has been derived from the unlawful actions of the police, the exercise of the warrantless search power may be unreasonable in terms of s 21 of the New Zealand Bill of Rights Act 1990: see, for example, R v Hjelmstrom (2003) 20 CRNZ 208 (CA) (consent to presence on property obtained through misleading the occupant). See also Lord v Police (1998) 5 HRNZ 92 (HC). However, even where the police presence at a place is without lawful authority, drugs seized in the course of the exercise of the search power on reasonable grounds may be admissible under s 30 of the Evidence Act 2006: see, for example, Eruera v R  NZCA 288 (cannabis seizure in course of executing invalid search warrant for stolen property). For an example of evidential material discovered in the course of an unlawful search being held to be inadmissible, see R v Yeh  NZCA 580.
This new legislation gives no guidance to the police about what they may do when they enter private property subject to an implied licence.
Your own jurisdiction may well have the same uncertainties as mine. To what extent do common law powers exist in the context of legislation? Do the police have greater common law powers than ordinary members of the public regarding entry onto private property? What are the terms of any implied licence to enter that apply to police officers? Does the characterisation of an entry as a search depend on privacy or on property rights? What sort of detection devices may be used in relation to private property pursuant to the common law?
People unfamiliar with the law's delays might be surprised that these questions can remain after 800 years. Good legal advice would be to set aside a further 800 years for the answers to emerge.