Dexter, Showtime's popular series about a cop, played by Michael C. Hall, who "channels" his compulsive killer instincts into a secret life as a vigilante, will make its debut on CBS Television on Feb. 17. The corporate parent of both CBS TV and Showtime is CBS Corp. The cable TV series, which employs graphic sex and violence, will require heavy editing to comply with FCC rules for broadcast network television. It will mark the first time that an entire season of a cable TV series will be rerun on a broadcast network. On Monday Writers Guild of America officials observed that the show's writers will not be able to contribute to the editing and that the episodes will therefore have to be edited by production personnel who have little understanding of story development and exposition.