Copycat for some reason wants to be some sort of intelligent, analytical thesis on what makes a killer, but, it fails miserably. For starters, the ending is idiotic; heavily placed so that the message the movie is providing tries to be truthful and convincing. The rest of the movie basically revolves around vignettes (or flashbacks) from the lives of Gein, Dahmer, and Ramirez, and the "relationship" between the journalist with the cop who helps her, and the serial killer who she wants to kill. Everything is kept at a nice pace, but the clichéd, redundant script and weak acting f*ck everything up to the extent that you don't care for any nice pace; you just want the damn movie to end.
The cinematography and editing are adequately done, the main score is effective, and the gore is bland for the most part.
Either way you look at this movie, be it from a critical or gore-fix (?) point of view, you should skip it. Hell, you shouldn't even read the plot synopsis on the back of the DVD box. Ignore this crap fest.