Related for Bekhorot 70:14
בכור בי כהן צריך שנים מן השוק להעיד עליו
Rabbi says: Even the evidence of ten people is not accepted if they are members of his household.<span class="x" onmousemove="('comment',' Whereas even one independent person is trustworthy in these matters, or according to R. Joshua, two independent persons. Now the first Tanna mentioned above is in agreement with the view of R. Joshua. for the first Tanna holds that shepherds who are priests, whether with Israelite or priestly employers, are not trustworthy, but independent priests are trustworthy, even as regards firstlings of priests. R. Meir says that even an independent priest is suspected, a view which is opposed to that of R. Joshua. Rabbenu Gershom interprets this as follows: The first Tanna who says that Israelite shepherds even in the employ of priests are trustworthy does not agree with R. Joshua's view, for according to the latter only independent priests are trustworthy. But R. Meir agrees with R. Joshua that we only suspect the priest's testimony where there is dependence on others, but the evidence of two independent priests is accepted.');"><sup>7</sup></span>