What does it really mean to say that you “possess” property? Generally, it means that no one else can say that they possess that same property. It’s exclusively yours.
If someone is hoping to gain title to a piece of property through the legal concept known as adverse possession, the possession of the property in question must be exclusive. This means that the trespasser cannot share control with other users, such as the property's true owner, neighbors, other trespassers, or the general public.
Let’s say you yourself plan to pursue a claim for adverse possession over a piece of property that you’ve been using for a long time, although on paper, it is owned by someone else. You’ll need to be able to establish that, during a certain number of years (the “statutory period” set by your state’s law on adverse possession), the disputed land was not freely open to the use of others, nor jointly possessed by others.
Like the legal requirement that a trespasser’s conduct must be “open and notorious” in order to support a claim of adverse possession, your exclusive possession of the land must be in a manner similar to the typical conduct of a true owner. Your use of the land must not only exclude the true owner, but also other trespassers, in the same way that the owner himself would be expected to exclude trespassers.
A trespasser cannot be said to occupy land exclusively if anyone thinks that they can freely use it. Imagine that a would-be adverse possessor seeks to establish title over a vacant lot in a neighborhood, which is technically owned by a neighbor. If everyone else in the neighborhood regularly uses that lot for block parties and baseball games, the would-be adverse possessor has a problem. He cannot establish that his use of the vacant lot is exclusive, since apparently, the general public believes that the land is open for their use as well.
A trespasser can show exclusive control over a piece of land in any number of ways. Erecting physical improvements on the property, such as houses, sheds, decks or furniture, is most common. Hanging “Keep Out” signs, or putting fences around the land are also strong indicators.
In the absence of these tangible pieces of evidence, a trespasser’s substantial activity or physical presence on the property can establish exclusivity. All of these things – whether “Keep Out” signs or pieces of furniture – put everyone on notice that this piece of property belongs to the trespasser and the trespasser alone.
Remember, the trespasser must use the land as a true owner would. If the land in question is a backyard, for example, this might mean sometimes bringing friends onto the lawn area to have a barbecue. It might mean playing football there with one's son. Or it might mean hiring handymen to come onto the lawn and install a deck.
All of these examples bring other people onto the land that the trespasser is required to be exclusively holding. Courts generally hold that this is legally acceptable, however. Allowing others to use the property does not necessarily negate the exclusivity requirement for adverse possession, since the true owners of that property would also likely have friends or workers or family members join them there at times.
As long as those people don’t also exercise possession over the land – and they know it’s “yours” – you are still adversely possessing it. A mere casual intrusion by others onto property occupied by an adverse claimant does not deprive his or her possession of its exclusive character.