I have been down into the sewers and got harphs diary. I then talked to tinthan about him going down there i have also got the other testimony and the arrest warrent. But when i go to arrest Harph he says something about tinthan and attacks me. It will not let me arrest him idk if this is a bug or i am missing something along the way. Also i am playing as a paladin not sure if this matters. Thanks in advance

I arrested him before I talked with Tinthan, so he was pretty sure that I cannot prove him guilty since he claimed he's illiterate to write a diary. May be that's the difference. Also I had high authority skill, I don't know if it matters.