More on Rabbi Hiya and the kal va-chomer of agreeing to part of a claim - with an actual case! (including a partial agreement to a claim as established by testimony, which would require him to swear... unless he's a thief, and therefore exempt from swearing). Plus, "shevuat heseit." Also, the potential of shepherds to steal, tacitly, while the flocks graze elsewhere (but that's a private shepherd, not a public shepherd). Also, the fact that one who is suspected of thievery is trusted to take an oath (or maybe not).