The Shulhan Aruch (Hoshen Mishpat 378), in his discussion of liability for damages, rules that a person must pay for damages he causes even if he causes them unintentionally. A person is held liable despite the fact that he had no intention to damage the other party’s property, and did so accidentally.
An important exception to this rule is a case where the damage occurred when the victim entered the person’s property without permission. An example would be a situation where a person is working on his roof, and somebody carrying luggage arrives at the front door. Seeing that nobody answered the door, the visitor goes to the backyard to try to backdoor, and his luggage is damaged by the tiles which the homeowner throws from the roof. The visitor – who was trespassing on the property – cannot claim compensation from the homeowner. Since he entered the property without the homeowner’s permission, the homeowner is not liable for the damages caused to his belongings.
This only applies, however, if the homeowner did not see the visitor. If, however, he sees the visitor, he must be careful not to hurt the visitor or damage his possessions, even though he did not grant him permission to enter his property. Of course, he has the right to demand that the uninvited guest leave his property. However, he is not absolved of liability for damages caused to the visitor.
Summary: If a person enters someone’s property without his knowledge, the homeowner is not liable for damages he inadvertently causes to the visitor’s possessions. Once he knows that the person is on his property, however, then although he is entitled to demand that the person leave, he is responsible for damages he causes to that person’s belongings.
