He was a psychiatrist who wrote a psych evaluation on Travis Marshall.
During the investigation of Santa Maria de Laredo, Dexter finds two empty prescription bottles being used for paint thinner. One of them is for Chlorpromazine that had been prescribed for Travis Marshall in 2006 by Dr. Carlson, a Miami doctor. Two refills are still left five years later.
Detective Mike Anderson researches Dr. Carlson and the medicine. He learns that Carlson died two years ago of unknown causes, though Mike did obtain his file on Travis. According to Carlson, Travis suffers from "breaks from reality," "violent tendencies since childhood," and a "lack of empathy." He's also a "master manipulator" and has "delusions of grandeur." Carlson believed that Travis, during his childhood, was responsible for the deaths of both his parents, having grabbed the steering wheel to force their car into a tree. Carlson prescribed Chlorpromazine for Travis which is used to treat psychotic disorders such as schizophrenia or manic-depression, and can help decrease hallucinations.
The medicine was either not effective, not taken properly, or discontinued by Travis, as he killed Professor James Gellar while under the belief that he and Gellar were chosen by God to bring on the End of Days.
- 2006 - Dr. Carlson prescribes anti-psychotic meds for Travis
- 2008 - Professor James Gellar is murdered by Travis
- 2009 - Dr. Carlson dies
- 2011 - Doomsday Tableaus are carried out by Travis