He ceded the role of head writer to fellow executive producer Clyde Phillips after the pilot episode was produced, and had very little involvement in writing the remainder of the season. After the season ended, Manos left the show altogether.
He was credited as executive producer for all of Season One.
Prior to working on Dexter he acted as a writer and producer on various shows, including The Sopranos and The Shield. Since working on DEXTER, all his subsequent work has been as a producer, with only two further writing credits.