Eugene Volokh has this post at the Volokh Conspiracy highlighting the recent case of State v. Davis in the New Mexico Supreme Court. In that case, police officers observed property by flying over it at a height of fifty feet in a helicopter. The Court held that the intrusiveness of this surveillance, which apparently included broken beams and solar panels, rendered the flyover a Fourth Amendment search.
The Court also criticized the New Mexico Court of Appeals ruling on the case, which noted that intrusiveness should not be the metric for determining whether a search has occurred because officers may use drones to conduct equally low flyovers without the noise, dust, and damage of a helicopter flyover. The New Mexico Supreme Court pointed out that the Court of Appeals' discussion was unnecessary speculation.
This approach is consistent with the United States Supreme Court's approach in United States v. Jones, in which the majority held that officers had conducted a Fourth Amendment search when they attached a GPS device to a car and tracked it for a prolonged period of time. Rather than hold that the prolonged gathering of information rose to the level of a search, the majority concluded that the act of attaching the GPS device was a physical trespass and therefore violated the Fourth Amendment.
While the Davis court only makes a passing reference to Jones, the Court is correct to conclude its analysis with its discussion of intrusion, as such an intrusion is sufficient to establish a Fourth Amendment violation. Going beyond the intrusiveness discussion is therefore unnecessary to resolve the question presented.
But one day, the question will be presented as to whether a low-flying police drone constitutes a Fourth Amendment search. When that question arises, the drones involved likely will not kick up the dust, incite the panic, or cause the damage that is the central focus of the Davis Court's decision. When that day comes, courts may find themselves constrained by the precedents cited in Davis which uphold the constitutionality of aerial observations. This will be especially true if state and federal laws are drafted in a manner that gives ordinary drone users a wide range of freedom in flying their drones, as common drone use will form the foundation of people's reasonable expectations of privacy.
Courts can be rescued from these difficult decisions, however, if states draft rules regulating the use of evidence obtained by police drones. State legislation can be drafted in a manner that balances law enforcement interests with privacy interests -- and this balance can be reached through debate and public input, rather than through speculation and generalizations that may arise from a single case before a deliberating court.
For those readers interested in hearing more on what I have to say on state drone laws, check out my article on the subject which was just published by the Harvard Journal on Legislation. You can find that updated version on SSRN as well.