In Storm Front, Carmichael is described as being short, overweight and balding, with a rather light, nasal voice, beady, bloodshot eyes and a weak chin, which all served to conceal a razor intellect. He is a sharp cop, and absolutely ruthless at tracking down killers. He is Karrin Murphy's partner, and a skeptic, convinced that Harry Dresden is a charlatan, scamming the city for his consulting fees.
In the series
"Welcome to the Jungle"
In "Welcome to the Jungle", Carmichael is of the opinion that the best course to solve Maurice Sandbourne's murder is to pin it on Moe the gorilla. Karrin Murphy, however, disagrees, and hires Dresden to investigate the case.
In Storm Front, Carmichael is at Jennifer Stanton's murder scene and is again dead set against Harry Dresden. Later, Murphy uses him as a witness when talking to Dresden; he wants to arrest the wizard.
In Fool Moon, Carmichael is less hostile to Dresden than before, even though he still thinks Dresden's not on the level. Carmichael pulls Dresden away from the loup-garou. Soon after he is killed, when the loup-garou tears through the station. He lost his life protecting Karrin Murphy. His funeral was attended both by Murphy and Dresden.
In Ghost Story, Carmichael made a return as his 30 year old self working in Between. He yelled at Harry Dresden to get off the track before the train came and when Dresden belligerently poked his chin at the train, Carmicahel hauled him up on the platform. He said the Southbound Train came pretty quickly lately and that he didn't think Dresden wanted that train. Then he took Dresden to meet with Jack Murphy in the Office. Later, when Uriel was giving Dresden the choice to go work in the Office of Chicago Between, Dresden saw Carmichael through the glass door. He was reading his notes and fishing for his keys.