Apparently, I know who murdered my friend's sister-in-law (my friend's name would be Pam). There's no evidence of it, but the killer would have told Pam's mother-in-law that he killed her daughter. And Pam told me, not sure why. The reason why it's a secret is that it's 100% sure that Pam's s/o is gonna kill the murderer and he knows for sure who it is. So I'm not even really sure about it, but I feel very weird that I can't tell Pam's s/o. Also, Pam's mother-in-law is now deceased (a few years ago). It was such a long time ago and they already investigated, so I don't really see myself going to the police, I think it would just cause problems...