Q: When we bought our house in D.C. two years ago, we were told by the former owner that a boundary problem existed between our lot and our neighbor's. When the house was rehabilitated by the former owner, a fence was constructed, which is four feet inside of our boundary line. I am not sure how long our neighbors have been using the space, and since we are paying taxes on the property, we would like to reclaim it.

How do we go about recapturing that space?

A: There is a very old doctrine in the law known as "adverse possession." If we go back to our history books, this is also known as "squatter's rights."

The theory of the doctrine of adverse possession is that the person who hold or uses property adversely against the rightful owner should ultimately be entitled to clear title. But not every possession of land will turn into fee-simple ownership. The possession must be hostile, actual, notorious, exclusive, continuous, and under claim of right.

Needless to say, these sound like highly complex legal concepts, and to some extent they are. However, in the words of one judge, "The person claiming property by adverse possession must unfurl his flag on the land and keep it flying so that the owner may see, if he wishes, that an enemy has invaded his domain and planted the flag of conquest."

Thus, the stranger on the land (the person claiming by adverse possession) must do something to alert the true owner that the stranger has taken occupancy.

Turning to your specific question, the law in the District of Columbia is that a person obtains valid title to land if the adverse possession is for a period of 15 years. Since you have stated that your do not know how long your neighbors have been using the space, it is incumbent upon you to immediately attempt to regain the land. I would suggest that you obtain a survey of your property, tear down the fence, and put the fence back on the proper boundary line.

Bear in mind that the burden of proof is on the claimant to meet the tests for adverse possession. In order to actually get title to this land in question, your neighbor will have to file a complaint in court in what is known as "an action to quiet title." Needless to say, this is both time-consuming and expensive, and your neighbor may not be inclined to go ahead with this action.

In the District and in Virginia, the claimant of property under the doctrine of adverse possession must meet all of the various elements for a period of at least 15 years. In Maryland, the law requires 20 years for a successful claim.

Benny L. Kass is a Washington attorney. Write him in care of the real estate section, The Washington Post 1150 15th St. NW, Washington 20071.