Trespass
Trespass is a physical invasion of a property owner's land. A person may be liable to the owner if he causes a trespass, even if he did not know that it was the owner's land.
Ways to commit trespass
A trespasser may be liable for trespass if he personally enters the owner's land, causes another person to enter the owner's land, causes an object to enter the owner's land, or remains on the land after his legal right to do so ends.
Intent
A trespasser may be liable if he intended to enter the owner's land with the knowledge that it was the owner's land. He may also be liable if he entered the owner's land by mistake and without knowledge that it was the owner's land, as long as he intended to enter that particular land.
What is land?
A trespasser may be liable if he causes a trespass on the land itself, in the air above the land, or in the ground under the land. For example, if a neighbor's tree hangs over an owner's land, the neighbor may be liable for trespass.
Damage
An owner is not required to prove that the trespasser caused any actual damage to the land.
Emergencies
When there is a necessity to do so, a person may enter an owner's land. However, he will be liable for any actual damages that he causes. For example, if a pilot of a plane in distress lands the plane on an owner's farm, he will not be liable for the tort of trespass, but he will be liable for any damage caused to the crops.