According to article posted on CSI Files...
Mendelsohn revealed that fans can expect to see a familiar nemesis during the new season. “[Season 12] will be focused a lot on the comeback of that slick, elusive and all dressed-in-latex serial killer called Sqweegel,” she said, echoing statements from fellow executive producer Don McGill. Mendelsohn added, “This character was created by Anthony Zuiker, the creator of the show, for his book Level 26.” Fans first saw the forensic-proof killer in the episode named after him,“Sqweegel”.
Okay, now I liked "Sqweegel" but must we have another serial killer arc again? Can they not come up with a season without a serial killer anymore? I can stand Sqweegel for one, maybe even two more episode, but please, please do not overdo it and pull another Haskell, where they had it too much and made us bored with him after awhile.