Recent unfortunate events - the killing of a zoo worker in Jerusalem by a leopard, and the decision to kill all the crocodiles at the Petzael farm - raise the question:
Is there a basis in halacha to execute an animal that killed a person? And is there any authority to do so in our times?
Obligation of Execution for an Animal That Killed a Person
The halacha stipulates that an animal that killed a person is liable for death, even if it's the first time it harmed a person (i.e., even if it is considered "a tame ox"). This is ruled by Maimonides in the Laws of Monetary Damage (Chapter 10).
In the Mishnah in Tractate Sanhedrin (Chapter 1, Mishnah 4), two opinions are brought regarding the method of execution:
According to Rabbi Eliezer: "The sooner it is killed the better", and anyone has the right to kill it immediately.
According to the Sages: The animal must be brought to trial before a court of 23 judges, similar to the capital cases of humans.
The opinion of the Sages is the one ruled in halacha by Maimonides (Sanhedrin, Chapter 5, Halacha 2):
"Capital cases are not judged with less than twenty-three, which is a small Sanhedrin - whether the capital cases of a person or of an animal... even a lion, bear, and cheetah that killed - their execution is by twenty-three. But a snake that killed - anyone kills it."
In other words, only animals that are not naturally dangerous and are owned require a trial before an authorized court. In contrast, a snake that killed can be killed immediately.
Additionally, Maimonides explains (Monetary Damage, Chapter 10, Halacha 6) that the method of execution is stoning.
Authority to Execute an Animal in Our Time
Is there halachic authority nowadays to order the execution of an animal that killed a person?
Since capital cases require a court of twenty-three ordained judges (ordination "man from man" going all the way back to Moses), and in our generation there are no ordained judges, it seems there is no regular halachic authority to judge the animal to death.
However, several later authorities have suggested possibilities for action even now:
The commandment "and you shall clear out the evil from your midst" - some see it as a basis for temporary measures even in our time, without an ordained court (Responsa Yad Eliyahu, Siman 35; Chacham Tzvi, Siman 4; although Maharil Diskin, Kuntrus Acharon, Siman 5, letter 143 - disagrees).
The authority of a court to act according to necessity is ruled in Shulchan Aruch (Choshen Mishpat, Siman 2) that "any court, even if not ordained... if they see the people commit transgressions... they would judge by death or money... even if there is no complete evidence."
Accordingly, if there is a specific and reasonable reason for the court to execute the animal, it might be seen as a justified step within the framework of "temporary necessity."
Conclusion
Based on reports about the real danger posed by the crocodiles at the Petzael farm, and on previous cases of attacks by them, there is halachic room to order their killing, even today.
Similarly, in the case of the leopard that killed the zoo worker, there is a halachic basis supporting this decision, out of consideration for public welfare and the need to protect human life.
This article is written as an exercise in Torah study, intended for halachic clarification and public education, and is not meant as a practical ruling.