On the US TV series "Dexter", which of these characters was not a police officer?

Dexter Morgan is a Miami-based blood splatter expert; he is not an official and certified police officer. He however doesn't just assist police authorities in solving murders; he commits them too. In fact, he's a serial killer -- but he only murders the guilty, so he feels justified with his lifestyle choices. His policewoman sister (Debra Morgan) and his cop co-workers have no idea Dexter lives a double life. His adoptive father however Harry Morgan(a police officer) knows his secret, and does, in fact, help Dexter hone his "skills". It's a unique brand of justice for which charming Dexter feeds a psychological hunger.

The TV series "Dexter" is an American crime drama series that aired on Showtime from October 2006—September 2013. Set in Miami, the series centers on Dexter (Michael C. Hall). He is a very skilled forensic technician specializing in bloodstain pattern analysis for the fictional Miami Metro Police Department. He has a real secret parallel life as a vigilante serial killer, hunting down murderers who have not been adequately punished by the American justice system due to corruption or legal technicalities.

Dexter lives by a strict code of honor that is both his saving grace and lifelong burden. He is truly torn between his deadly compulsion and his desire for true justice.