Adam Clarke on Exodus 22:13

If it be torn in pieces - let him bring it for witness - Rather, Let him bring עד הטרפה ed hatterephah, a testimony or evidence of the torn thing, such as the horns, hoofs, etc. This is still a law in some countries among graziers: if a horse, cow, sheep, or goat, entrusted to them, be lost, and the keeper asserts it was devoured by dogs, etc., the law obliges him to produce the horns and hoofs, because on these the owner's mark is generally found. If these can be produced, the keeper is acquitted by the law. The ear is often the place marked, but this is not absolutely required, because a ravenous beast may eat the ear as well as any other part, but he cannot eat the horns or the hoofs. It seems however that in after times two of the legs and the ear were required as evidences to acquit the shepherd of all guilt. See Amo 3:12.