When Carl is presented with the letters Kimmie has written to Ditlev, proving her to be an unreliable witness, he has a marked subconjunctival hemorrhage (a bleed onto the white of the eye) on his right eye, consistent with him having been whacked on the head with a metal pipe by Kimmie. When he interviews her in the cells minutes later, it is gone. They normally take a week or so to clear up.