Sefer Chofetz Chaim hilchos rechilus chapter 6 halachos 8,9

Halacha 9: Even if someone speaks rechilus mesiach lifi tumo, meaning it just came out in a story that someone did or said something to someone else, and there was clearly no intention of the speaker maliciously wanting to tell on the guy, then even though there is more reason to believe the story still one cannot conclude it’s the truth and accept words of rechilus.

Halacha 10: If there is circumstantial evidence for the rechilus there are 5 rules that must be met to be able to accept it as truth.

1. The circumstantial evidence must lead us to believe that the rechilus is true and there can’t be any possible way to judge the suspect favorably.

 2. The evidence for what the suspect did or said has to be absolutely recognizable not just slightly recognizable.

3. The person speaking the rechilus would have had to have seen the evidence firsthand, not heard through other people.

4. Only if knowing this evidence will be useful for the listener or others in the future can it be used to allow rechilus to be said. If there is no use for anyone to listen to this, then people anyways can’t listen to rechilus even if it has circumstantial evidence backing it up.

5. Circumstantial evidence only allows one to believe in one’s heart that what he heard is true but that does not mean he can now go tell it to someone else unless of course it will be helpful for people to know for the future. He certainly can’t take matters into his own hands and monetarily or physically hurt the suspect. If a court cannot act on circumstantial evidence to execute someone or hold them monetarily responsible for damages, unless there are two witnesses that testified then certainly one may not act on his own accord. He must go through the courts to take action. This only help to take proper precautions for one’s safety, monetarily, physically, and psychologically.

A proof that circumstantial evidence doesn’t work to take action is a case in Bava Basra 93a where a known to be goring ox was seen chasing another ox and then it ran into a meadow, and they were both found later with the goring ox standing over the other ox with bloody horns and the other ox lying there with fresh blood spurting out. It seems obvious that the goring ox gored the other ox still in all the peak is in Choshen Mishpat 408:1,2 that if there isn’t completely clear evidence of the incident, like two witnesses seeing the actual goring then the owner of the goring cow isn’t even liable in court, certainly action can’t be taken outside of court.

Another case quoted in the name if the Mahari”k from gemara Sanhedrin 37b which proves the point is of a person seen running after another with a sword and they turn the corner into an alley and afterwards the chaser is found with a bloody sword in hand standing over a dead body,, but he is not sentenced to death since there were not 2 witnesses that actually saw him kill. The Mahari”k says this also applies to monetary damages no matter how apparent it might seem the court can’t just make the suspect guilty if it’s not absolutely clearly what happened, like with 2 witnesses testifying, so certainly people can’t take matters into their own hands.