When the Chosen One is talking to Jo to receive the "investigate the ghost farm" quest, they can ask him to cut off his right pinky finger. Should he go ahead bad Karma along with the the mutilated finger will be received, it is also possible to stop Jo by realizing he is serious about the situation, allowing the poor man to keep his appendage. If told to "saute the finger in a butter sauce", after he cuts it off however, he will pull out a shotgun on the Chosen in response to the bad joke.
This option is only available with positive Karma, and only still if you don't have too much of it. 346 Karma suffice, which you can have if you did every quest until now and helped Tyler against Lara. But if you helped Lara (ca. 360 Karma), Jo outright rejects cutting off his finger, saying he's desperate, but not dumb.
If Jo dies, Bo takes his place as Justice of the Peace.