Diminished Value Law
The measure of damages for trespass is described in Harper & James, The Law of Torts § 2.6 (1956) states as follows:
No recovery can be had for trespass to chattels if no harm is caused thereby. If harm results, the trespasser is liable for all the harm to the chattel and to the person of its possessor proximately caused by the intermeddling. If the chattel is destroyed, its market value is ordinarily the measure of recovery, if the chattel has a market value. If it is damaged but still has value, recovery is limited to the difference between its market value before and after the intermeddling. If the chattel does not have a market value, many courts permit a recovery based on the actual value of the chattel to its owner in consideration of its utility and other matters specially claimed to add value, but excluding mere sentimental value.
“Where a person is entitled to a judgment for harm to chattels not amounting to a total destruction in value, the damages include compensation for:
(a) the difference between the value of the chattel before the harm and the value after the harm, or at the plaintiff’s election, the reasonable cost of repairs or restoration where feasible, with due allowance for any difference between the original value and the value after repairs, and
(b) the loss of use.
Comment on Clause (a)
The full value of a chattel which has been tortiously harmed but which has not been converted or made cempletely worthless, cannot be obtained by the owner; he cannot abandon it and recover its value in damages. He can recover only the difference in its value before and after the harm, except that if, after the harm, it appears to be economical to repair the chattel, he can elect to recover the cost of repairs, together with the value of the loss of use during the repairs, or other losses which may have resulted during such time. * If it does not appear to a reasonable person economical to repair or replace the damaged part, the damages are the full value of the subject matter at the time of the tort, less the junk value of the remains. Ordinarily, where the cost of repairs would be greater than the exchange value of the chattel before the harm, it would not be economical to make the repairs. If, however, the chattel has peculiar value to the owner, as where a family portrait having substantially no exchange value has been harmed or, where, to avoid injury to business, it is feasible to make expensive repairs rather than to delay in obtaining a new chattel, it may be reasonable to make repairs at an expense greater than the cost of a new chattel.