The only reason why the victim of the murder investigation happened was because someone else fucked up, she wasn't directly involved with it. She has the power, connections and mentality to just make people disappear without leaving any body, and this is also why I think that if it was her, FAR more violence would have been used. After all, Jade tends to move very independantly so her disappearing would only really alert Viv as no one else knows what Jade is investigating.
Wouldn't be surprised if it was the dude from the hospital, or the mayor for that matter. He's appearing far too "clean" for the setting and his position.