[If] a bechor was pursuing him, and he kicked it and inflicted a blemish upon it, he may slaughter on account of it. [For] all blemishes that can be inflicted by man, shepherds [who are] Yisraelim are believed, but shepherds [who are] Kohanim are not believed. Rabban Shimon ben Gamliel says: He is believed concerning his friend’s [bechor], but he is not believed concerning his own. R’ Meir says: One who is suspected concerning a thing may neither judge nor testify about it.