Sanhedrin, Chapter One, Mishnah Four
Mishnah four deals with the number of judges in cases involving capital crimes.
1) Cases concerning offenses punishable by death [are decided] by twenty three.
2) A beast that has sexual relations with a woman or with a man is [judged] by twenty three, as it says, You shall execute the woman and the beast (Lev. 20:16) and it says, You shall execute the beast.
3) The ox that is stoned [is judged] by twenty three., as it says, The ox shall be stoned and also its owner shall be put to death (Exodus 21:29), as is the death of the owner, so too is the death of the ox.
4) The wolf, the lion, the bear, the leopard, the panther, or serpent [that have killed a human being] their death is [adjudicated] by twenty three.
a) Rabbi Eliezer says: Anyone who kills them before they come to court merits.
b) But Rabbi Akiva says: Their death must be [adjudicated] by twenty three.
Section one: Capital crimes are adjudicated by a court of twenty three. This is certainly due to the gravity of the punishment, which is of course irrevocable.
Section two: According to Lev. 2O:15-16 when a man or woman has sexual relations with an animal, not only are the human beings to be executed but the animal as well. Our mishnah teaches that just as the human beings are judged by twenty three so too are the animals.
Section three: According to Exodus 21:28-29 if an ox kills a man or woman the ox must be stoned. If the ox was a warned ox, that is one that had previously gored, the owner of the ox is to be stoned as well. Our mishnah teaches, just as the human being would be judged by twenty three, so too the animal.
Section four: Not only are oxen who kill humans to be executed but any animal that kills a human. According to the first opinion in the mishnah, these animals are also to be judged by a court of twenty three. Rabbi Eliezer disagrees and says that the first person who sees them should kill them. After all, these animals which are wild and cannot be guarded as an ox can be guarded, present a hazard to the safety of the public. Rabbi Akiva disagrees with Rabbi Eliezer and states that they must be judged in front of a court of twenty three and only then can they be executed.