EXCLUSIVE: Naren Shankar is stepping down as executive producer/co-showrunner of CBS’ long-running crime drama CSI: Crime Scene Investigation. He has been on the show for eight years, serving as co-showrunner alongside Carol Mendelsohn for the past five seasons.

Shankar has one more year left on his overall deal with CSI producer CBS Studios and sources say the intention always was for him to focus on development towards the end of his pact. “It was time for him to flex another creative muscle,” an insider said.

Exec producer Mendelsohn, who has been on CSI since the beginning, building the CSI franchise with creator Anthony Zuicker and CSI: Miami showrunner Ann Donahue, is staying at the helm of the mothership series. The veteran forensic drama, now in its 10th season, has been showing significant ratings wear and tear, especially after the departure of star William Petersen last year, but it still does the job as CBS’ centerpiece series on Thursday night.