Bava Kamma, Chapter 4, Mishnah 7. We continue discussing the obligation to conduct a formal trial and execute an animal that intentionally killed a Jew. The section we learned previously repeatedly refers to a "baal" or "bealav" - the owner of the ox that killed. This raises the question: what is the law when the animal does not have an owner in the standard, accepted sense? Is it still liable to the same death penalty? The Tanna Kamma, and the halachah follows this, holds that it is liable.
In the Torah portion dealing with an ox that killed, the word "ox" appears seven times. The first time is necessary in its own right, while the six additional times come to include cases where we might have thought the ox would be exempt - because it has no owner, or because the law is contingent on the existence of an owner - and nevertheless, it is also liable to the death penalty.
The six cases the Torah includes:
"Shor ha'ishah" - An ox owned by a woman. Since the word "baal" (owner/husband) might imply specifically a man, the Mishnah teaches that there is no difference: even a woman's ox is sentenced to the same death penalty.
"Shor hayesomim" - An ox owned by orphans. We might have thought that since they are minors, they are not subject to the same requirements.
"Shor ha'apotropos" - Even when a trustee is appointed to oversee the children's assets, guard them, and care for their affairs. The financial losers from executing the ox are its owners, meaning the orphans themselves, and we might have exempted it for this reason. But this is not so: their ox, if it killed intentionally, is liable to the death penalty.
"Shor hamidbar" - An ox that became wild and ownerless, running around in the hills. It has no formal owner, and nevertheless, it is subject to the same laws.
"Shor hekdesh" - An ox owned by the Temple. There is no owner here in the accepted sense, since as it were, the Holy One, Blessed is He, and the Temple are the owners; and nevertheless, it is subject to the law.
"Shor hager shemes ve'ein lo yorshim" - A convert who died and left no heirs behind, and his ox reverts to being ownerless. It too is liable to the death penalty.
In this last case, we must understand: every Jew in the world has heirs, since someone will certainly be found in the family tree to be his heir, distant as they may be. However, a convert is like a newborn child, like a reborn person, and halachically his parents are no longer his parents. Therefore, there is a real possibility that this person will be left without heirs - if he had no children, or if he converted after having children who are not his heirs, and certainly not on a Torah level. Because of this, we might have thought that this ox was left without an owner, became ownerless, and is exempt - but this is not so.
And if you will ask: how is the "shor hamidbar" different from the ox of the convert who died?
Indeed, there is no essential difference between them, but rather they are two separate levels of novelty. One level: an ox that had an owner - the convert - but by the time it was brought to judgment in court its owner had already died, and the Torah teaches that it is liable to the death penalty. The second level, which is an even greater novelty: an ox that never had an owner at all, and nevertheless, it is liable, despite the term "baal". And we derive both of them, because six separate cases are required corresponding to the six additional times the word "ox" appears seemingly unnecessarily.
The view of Rabbi Yehudah:
"Rabbi Yehudah omer" - Rabbi Yehudah disagrees and holds that we do not expound anything from the extra uses of the word "ox" in the verses. Therefore, we take the verses simply, and animals that have no owners are not subject to the possibility of the death penalty. And because of this, "shor hamidbar" - the wild, ownerless ox, "shor hekdesh" - the ox belonging to the Temple, and "shor hager shemes" - an ox that belonged to a convert who died without heirs, all of these have no owners, and therefore, "patur min hamisah, lefi she'ein lahen bealim" - it is exempt from death, because they have no owners, as established in the verse that Rabbi Yehudah expounds.
The halachah: The halachah does not follow Rabbi Yehudah, but rather the Tanna Kamma. Indeed, in all six of these cases it makes no difference: if a cow, or any other animal or beast - and even a chicken - intentionally strikes a Jew and he dies, a formal trial is conducted. And following that trial, assuming the animal is "convicted" based on witnesses and the like, it is put to death.