Reference for Chullin 36:13
שמע רב יוסף איקפד אמר
As in the following statement: "Rab Judah said in the name of R'Jeremiah B'Abba (and I am in doubt whether he reported it in the name of Rab or in the name of Samuel) : Three ordinary persons may declare a firstling permitted for use where there is no specialist available"'.<span class="x" onmousemove="('comment',' The first born male of cattle was sacred and had to be offered as a sacrifice; if, however, it had a permanent defect it could then be slaughtered and eaten by Priests. It was for an expert to decide whether a particular defect was or was not permanent. If, however, the defect was obviously permanent and no expert was available, it is ruled that three lay men could come together and declare the first born animal permitted for use.');"><sup>8</sup></span>