Reference for Bava Kamma 82:14

And behold, on the week of the holy Shabbat of Parashat Toldot that year, two letters reached me speaking and advocating on behalf of the same man. And this is what I responded to them both at once: That which you wrote to excuse why you didn’t accept testimony, writing first on the basis of the statement of Maharam Mintz in Responsum 75, that testimony may not be collected for slanderous purposes, the response is self-evident: the present case is different, because the purpose is to keep him from sinning. I add that this is evident also from the case of a single witness, where we maintain that “Tuvia sins but Zigod [the lone witness] gets lashes,” yet Shulhan Arukh, Hoshen Mishpat 28 explains that to prevent someone from sinning, it is permitted [to hear a lone witness]. As to your honor’s contention that the content of the witnesses’ testimony is null since they are minors, I wrote the same in my responsum, so I do not understand [the contention]. Similarly, your honor’s contention that the testimonies are separate [i.e., they are not reporting on the same event], and to disqualify someone there must be a single testimony [by multiple witnesses to the same event], as it is like a capital case, I do not understand [the contention], for I said something even stronger – there is not even separate testimony, as he is like a hunter.