A trespasser can sometimes gain legal ownership of land just by occupying it. Here's how.

Homeowners have the right to keep unwanted intruders off their property. People may do this with fences or with signs, or just by asking trespassers to stay away. In cases of serious, repeated annoyance or threatened harm, a land owner can call the police, who will usually warn the person to stay away and, if necessary, make an arrest.

Another kind of trespass is more permanent: using another’s property as an owner would use it. If someone drives across your land every day, it is a trespass unless you have granted permission or the driver has a legal right, called an easement, to use that part of your property. A neighbor who puts up a fence two feet over the boundary line is trespassing, as is one whose garage has been on your property for several years.

Definition of Adverse Possession

You may be surprised to learn, that under certain circumstances, a trespasser can come onto your land, occupy it, and gain legal ownership of it. The legal term for this is "adverse possession."

Through adverse possession, a trespasser can gain ownership of just a few feet of property or hundreds of acres. And the trespasser doesn’t need to intend to take the land by adverse possession. Sometimes it happens through an honest mistake—for example, a neighbor may have relied upon a faulty property description in a deed when building a fence on your property.

How Adverse Possession Claims End Up in Court

Questions about legal ownership of property may arise in various situations, such as in the sale of a house. For example, a title insurance company may refuse to issue insurance when a property is sold because the neighbor’s garage is found to be standing squarely on the property.

If questions about ownership of land arise in this type of situation, and the people involved cannot work something out, then the issue may end up in court. The property owner may sue the trespasser (for example, the neighbor whose garage is encroaching), or the trespasser may bring a lawsuit to “quiet title”—a request for the court to settle who owns what.

Legal Requirements for an Adverse Possession Claim to Land

When courts look at adverse possession claims, they apply a four-factor test. To qualify as adverse possession, the trespasser’s occupation of the land must be:

hostile

actual

open and notorious, and

exclusive and continuous for a certain period of time.

This article discusses each of these elements. See your state law on adverse possession for details on your state rules. In addition to the legal requirements discussed below, some states also require the trespasser to have paid the local property taxes on the land during a specified time period.

Hostile Claim

The word "hostile" doesn’t mean that the trespasser rides in on a horse with six-guns blazing. Instead, courts follow one of three legal definitions of "hostile" when it comes to adverse possession.

Simple occupation. This rule (followed by most states today) defines "hostile" as the mere occupation of the land. The trespasser doesn’t have to know that the land belongs to someone else.

Awareness of trespassing. This rule requires that the trespasser be aware that his or her use of the property amounts to trespassing (meaning the trespasser has no legal right to be on the property).

Good faith mistake. A few states follow this rule, which requires the trespasser to have made an innocent good faith mistake in occupying the property in the first place, such as by relying on an invalid or incorrect deed.

Actual Possession of the Land

The second prong of the test that courts apply requires that the trespasser actually possess the property (be physically present) and treat it as if he or she were an owner. This can be established by documenting the trespasser's efforts to maintain and make improvements to the property.

Open and Notorious Possession

"Open and notorious" means that it must be obvious to anyone -- including a property owner who makes a reasonable effort to investigate -- that a trespasser is on the land. Examples would be a neighbor who puts a fence up slightly on the next-door property or who poured a concreted driveway two feet over the boundary line.

Exclusive and Continuous Possession

The trespasser must possess the land exclusively (that means the trespasser cannot share possession with strangers or the owner) and without interruption for a certain period of time. (That means the trespasser cannot give up use of the property, return to it later, and try to count the time that the property was abandoned as part of the "continuous" possession time period.) The time period that's required varies by state.

Also see What "Continuous" Possession of Property Means in Adverse Possession Claim.

How to Prevent Adverse Possession

If you are a landowner, keep an eye on your property. If you suspect that someone has a possible adverse possession claim, check property tax records to see if this person (or anyone else) has made tax payments on the property. To prevent a trespasser from gaining property ownership, you can take the following steps:

Post "no trespassing" signs and block entrances with gates. Keep in mind that this is a good way to deter trespassers, but in many states the fact that you have signs or gates won’t protect against a claim by a trespasser who takes possession of the land anyway.

Give written permission to someone to use your land, and get their written acknowledgement. For example, you could give someone permission to park on your land, use a shortcut across your property, or to garden or grow crops. This can not only defeat adverse possession claims, but also a claim to an easement (use permit) across your property.

Offer to rent the property to the trespasser.

Call the police.

Hire a lawyer. You may need to file a lawsuit to eject the trespasser from the landlord. Or you may want a court to order a structure removed from your property. You must act before the trespasser has been on your land long enough, under your state’s law, to make a successful adverse possession claim.

Getting Help With Trespassers

To learn more about adverse possession, how to prevent it, and other issues involving your land, get Neighbor Law: Fences, Trees, Boundaries & Noise, by Emily Doskow and Lina Guillen (Nolo). If you suspect that someone is trespassing on your land and you want to consult with a lawyer, Nolo ’ s Lawyer Directory can help you find a lawyer near you.

Some states require the trespasser to have paid taxes on the property for the designated time period. Some states require that the trespasser have some kind of document that would indicate ownership of the property--such as a deed or title--even if the document is legally invalid. See your state law on adverse possession for details.