Our story takes place in the (hopefully near) future:
A red calf was born in Yosef’s herd. He raised it with great care, protecting it from injury, and taking care not to work it in any way. As the calf approached two, he began negotiating with the Beis HaMikdash treasurers to sell them the cow for use as a parah adumah.
Yosef also brought it to a vet to make sure it didn’t have two black hairs, which would render it invalid. “Be careful not to lean on the cow,” Yosef warned him. “Even that is considered disqualifying work” (Mishnah Parah 2:3).
The vet began checking the cow. The sun shone strongly and it became hot, so Yosef went to get a drink. Meanwhile, the vet took off his jacket, neatly folded it, and slung it over the cow. When Yosef returned, he threw a fit!
“You used the cow for your jacket!” he screamed. “You caused me immense financial loss!”
The vet removed his jacket. “The cow’s in perfect shape,” he said. “The jacket did nothing to it. Look!”
“Halachically, though, any work done with the cow disqualifies it,” replied Yosef, “even placing clothing on it for one’s benefit!”
After leaving the vet, Yosef approached Rabbi Dayan and asked him if he could demand money from the vet for the loss he caused him.
Rabbi Dayan considered the question and said, “The Mishnah [Gittin 52b] discusses halachic damage that isn’t noticeable (hezek she’eino nikar). And it rules, for example, that if a person ritually defiled the tahor food of another, he is only liable if he defiled it intentionally [Choshen Mishpat 385:1].
“Although a person is usually liable even for accidental damage, Rabban Yochanan explains that, in this case, he is really completely exempt, but the Sages fined people who purposely damage property so that they won’t do so wantonly.
“Some compare hezek she’eino nikar to grama (incidental damage), which also does not carry legal liability” [Aruch HaShulchan 385:1].
“The Gemara cites a baraisa, which states that one who works with another’s red cow is legally exempt but will be punished by heaven. The Gemara’s discussion seems to indicate that he is exempt even if he worked the cow intentionally. However, the Rambam rules that he is only exempt if he worked the cow accidentally” [Chovel Umazik 7:4].
“The Raavad disagrees and explains that since, in principle, one is not liable for hezek she’eino nikar, the Sages fined an offender only when he causes damage maliciously to harm his fellow, not when he does so for his own benefit. The Rambam doesn’t make this distinction since the offender is aware of the harmful consequences of his action” [Meiri, Gittin 53a; see also Raavad on Rif, Kesubos 44b].
“The Ramban also exempts even an intentional damager from paying – but for a different reason. He follows the opinion that the Sages only imposed a fine in the particular, common cases of halachic damage listed in the mishnah.
“The Rambam [Chovel Umazik 7:2], though, follows the opinion that the fine of intentional hezek she’eino nikar applies to any case that’s similar to one of those in the mishnah. The Shulchan Aruch seems to follow this opinion as well” [Mishneh Lamelech, ibid.; Shach 385:1].
“The Acharonim debate,” concluded Rabbi Dayan, “whether accidental hezek she’eino nikar carries at least a heavenly punishment” [Pischei Choshen, Nezikin 1:53].