DEUT957 Do not judge on the basis of testimony from only one witness. Each of us has an element of baseness in him-- the yetzer hara (evil inclination). Sometimes, this baseness stirs up hatred in our heart for a fellow Jew. It can happen even to someone who is known for his righteousness. Suddenly, his whole state of mind changes, and he wants to harm a fellow Jew. For this reason, it is not fitting to accept the testimony if it comes from only one witness. We are forbidden to use such testimony to punish anyone, physically or otherwise, even if the witness is a noted Torah scholar and the accused is a lowlife with a criminal record. Only testimony of two witnesses can be accepted, for it is very unlikely that two Jews would conspire together and lie in court to harm someone.