The origin of the concept comes from the original writ of trespass de bonis asportatis. As in most other forms of trespass, remedy can only be obtained once it is proven that there was direct interference regardless of damage being done, and the infringing party has failed to disprove either negligence or intent.
In some common law countries like the United States and Canada, a remedy for trespass to chattels can only be obtained if the direct interference was sufficiently substantial to amount to dispossession, or alternatively where there had been an injury proximately related to the chattel. (See Restatement (Second) of Torts, 1965.)
The trespass to chattels cause of action, frequently asserted in recent years against Internet advertisers and email spammers, is often included in complaints against spyware companies.
To summarize, the basic elements of a claim of trespass to chattels are: 1) the lack of the plaintiff’s consent to the trespass, 2) interference or intermeddling with possessory interest, and 3) the intentionality of the defendant’s actions. Actual damage is not necessarily a required element of a trespass to chattels claim. See, e.g., Hawkins v. Hawkins, 101 N.C. App. 529, 532, 400 S.E.2d 472, 475 (1999).
a) Lack of consent
A vendor can attempt to dispute a trespass claim on the grounds that the user consented to the terms of the contract. Even if consent was given for certain access, a user may still have a valid trespass to chattels complaint if the vendor has exceeded the contractual terms, if the contract is found to misrepresent the actual functioning of the product, or if the consent has been withdrawn. A vendor can be held liable for “any use exceeding the consent” given.” (Restatement (Second) of Torts § 256)
b) Actual harm
The precise criteria for ascertaining actual harm varies among states, in California, for instance, an electronic message can be deemed a trespass where the message interferes with the target computer’s operation, as long as a plaintiff can demonstrate either actual hardware damage or actual impaired functioning (see: Intel v. Hamidi, 30 Cal.4th 1342 (2003)). But the general concept of requiring impaired computer functioning has been adopted consistently and in showing impaired computer functioning, courts have usually emphasized system unavailability.
In clarifying the meaning of intentionality in the context of a trespass to chattels claim, § 217 of the Restatement (Second) of Torts states that “intention is present when an act is done for the purpose of using or otherwise intermeddling with a chattel or with knowledge that such an intermeddling will, to a substantial certainty, result from the act,” and that, furthermore, “[i]t is not necessary that the actor should know or have reason to know that such intermeddling is a violation of the possessory rights of another.”
Damages from a trespass claim are limited to the actual harm sustained by the plaintiff (which can include economic loss consequent on the trespass - e.g. loss of profit on a damaged chattel). In cases of dispossession, the plaintiff is always entitled to damages if they can prove the dispossession occurred, even if no quantifiable harm can be proven.
A related tort is conversion, which involves an exercise of control over another's chattel justifying restitution of the chattel's full value. Some actions constitute trespass and conversion; in these cases, a plaintiff must choose which claim to make based on what amount of damages they seek to recover.