Greggs is a tenacious investigator and a rookie homicide detective. Postdoctoral researchers typically work under the supervision of a principal investigator. An early recorded professional criminal investigator was the English constable. He played Tom Buckley, the assistant to Weaver's character who is a paranormal investigator. Coco (David Dastmalchian) is a police forensics investigator. He played Frank Gaad, an FBI counterintelligence investigator. Enrico Colantoni played Veronica's father Keith Mars, a private investigator and former Balboa County Sheriff. Puthoff worked as the principal investigator of the project. In earlier stories, he is identified as the "World's Greatest Paranormal Investigator". Nifong hired Linwood E. Wilson as his chief investigator. Zaffis has over forty years of experience as a paranormal investigator. He was a principal investigator on 14 OSRD contracts. Corman initially planned to develop a story involving a private investigator. William F. King was the chief investigator for the case. The principal investigator was Paolo D'Arrigo.