Question: My neighbor got a small drone recently and he's been flying it around the area. I think there's a camera attached to it. The thing is, I grow some marijuana plants in a greenhouse in my backyard. Although the backyard is surrounded by a solid ten-foot fence, I'm worried about the drone. I live in a state where growing marijuana for personal use (let alone sale) is illegal. If my neighbor's drone takes photos through the glass panes of the greenhouse, could the photos be used by the cops to bust me?
Answer: Yes, on the facts you've presented. But your neighbor himself may be breaking the law or inviting a lawsuit. In general, it is legal to fly a drone, but there are some restrictions.
Your neighbor is snooping by drone on your greenhouse in a way that is similar to surveillance sometimes carried out by law enforcement agencies. Under the U.S. Constitution, police usually must obtain a search warrant, based on probable cause, to search your property. But because the drone owner is a private citizen and not a police officer, you don't have the constitutional protections against unreasonable searches that you would have against a cop. For this reason, if the neighbor brings the photos to the cops, they could use them to support their request for a warrant to search your property. The reason is that they didn't participate in the search—they were just the innocent recipients of the neighbor's snooping.
Contrast this conclusion with the following scenario: Your neighbor, suspecting that you're growing pot in your backyard, goes to the police and tells them the basis for his suspicions (lots of comings and goings by various people at odd hours; an unusually large greenhouse in an otherwise barren backyard; grow lights that are on constantly and are visible from the neighbor's property). The police suspect a "grow" operation, but tell the neighbor that this is not enough evidence to support a warrant. Challenged, the neighbor fires up his drone, sends it over your yard, and takes clear pictures of your pot plants. He cheerfully takes them to the police, who attach them to their request for a warrant, which a judge issues.
In this scenario, your defense attorney might argue that the neighbor is acting as an agent of the police, and because of that, the search he carried out must be evaluated as if the police themselves conducted it. Your lawyer would look for evidence that the police encouraged the neighbor to keep working at getting enough evidence to support a warrant. In short, if the defendant could show that the neighbor was being directed by the police, he may be able to get the evidence suppressed, or tossed out, as the fruit of an illegal search. (In this scenario, both the evidence uncovered by the neighbor while acting at the police's direction and the evidence acquired by the police in executing the search warrant would be subject to suppression.)
Alas, there's one possible glitch to even this happy result. No one has a right to suppression of evidence from a search that occurs from a public place, involving a situation in which there is no reasonable expectation of privacy from drone or human alike. For example, if your greenhouse and its clear windows can be seen and photographed from a helicopter, or seen clearly by a utility repairperson high up on a telephone pole, you have no grounds to object when people in those positions take pictures. Arguably, the drone is no different than the helicopter.
If you see the drone venturing below 500 feet (1,000, if you live in a city), your neighbor may himself be breaking the law. Although drones are not presently regulated by the Federal Aviation Association, if the drone drops below "navigable airspace" (the altitudes mentioned above), it may be trespassing on your property. In that event, a garden-variety complaint to the police, alleging trespass, might be possible. Additionally, the drone may be venturing into space that is regulated by local laws.
Though you might consider destroying the invasive drone, there are other ways to strike back. A complaint to local authorities concerning the drone's trespass or by threatening or filing a civil lawsuit is possible, but think twice before going on the offensive. Doing so might inspire your neighbor to do just what you fear—send the photos to the police. It may be better to just ask him nicely not to fly his drone over your yard because it disturbs your daily meditation. And you might want to think about quitting—or at least relocating—your growing endeavors.
You may want to run all of this by a seasoned criminal defense attorney familiar with the law in your state. Even search-and-seizure law can vary somewhat from one state to another. And a knowledgeable lawyer can advise you of your options—and their risks. Although you may be worrying for nothing (because my guess is your neighbor is just hoping to get shots of people sunbathing naked on their patios), a bit of counsel may help you sleep at night.