I saw recently a story about the Gra that two witnesses came to him about a certain case. I forget the case but it was about something sexual. And it must have been significant enough for the Gra to agree to listen. He told one witness to stand outside while he listened to the other. Then they brought in the other witness. He said the exact same testimony. As soon as he finished speaking the Gra said "They are liars."
The people that had brought them did not understand how he was so sure. Afterwards he explained.
The Mishna says when two witness come you examine them and if their testimony is found to correspond then they are believed. The Gra asked why does the mishna add that about being found to correspond?Why not just say the testimony corresponded? He said because it has to be "found." It can not be the same exact thing. No two people seeing the same event or hearing the same person talk will report the same details.