Halakhah su Deuteronomio 19:16

Not to have a sinner testify: That we not accept the testimony of a man who sins, and we not do anything on account of his testimony, as it is stated (Exodus 23:1), "do not place your hand with an evildoer to be a violent witness." And the explanation comes about this (Sanhedrin 27a), "Do not place an evildoer as a witness, do not place a violent one as a witness," meaning a violent person - to exclude violent people and thieves who are disqualified from testimony, as it is stated (Deuteronomy 19:16), "If a violent witness comes upon a man."

He prohibited the judge - that he not accept testimony of a sinner and not do anything based on his testimony. And that is His saying, "Do not place your hand with an evildoer to be a violent witness" (Exodus 23:1). And the explanation appeared (Mekhilta d'Rabbi Yishmael 23:1:2) - "Do not make a violent one a witness; to exclude thugs and robbers from being witnesses - as it is stated, 'If a violent witness rise up' (Deuteronomy 19:16)." And the regulations of this commandment have been explained in Chapter 3 of Sanhedrin. (See Parashat Mishpatim; Mishneh Torah, Testimony 10.)