Peter Foley: Did you know, Helen, that more books have been written about Jack the Ripper than Abraham Lincoln? It's a sick world, isn't it, Helen?
M.J. Monahan: Nobody in this department has ever worked a serial case before.
Lt. Quinn: Whoa, whoa, whoa, whoa, whoa. I have.
M.J. Monahan: The Zodiac, right?
Lt. Quinn: That's right.
M.J. Monahan: Did anyone ever catch the Zodiac, sir, or did he die of old age?
Daryll Lee Cullum: I'm death and life to you, doc... death and life.
Helen Hudson: He really wants us to think what he's doing is art.
Daryll Lee Cullum: Why don't you say a you and me have a little bit of fun?
Answer: I thought that it was Peter Kurten (Foley) that broke in and left the book. However if it was Conrad, then he does not appear in the flesh in the film.
Alan Keddie
You are correct. I just rewatched this tonight on Tubi.