The plastic "blue bag" that Tony Hill is often seen with was gleaned from Robson Green's research for Wire in the Blood, which involved spending time with revered criminal psychologist Julian Boon, who Green describes in part as an "extraordinary, intelligent, nice guy who carried his life in a blue bag and travelled on a double-decker bus. No-one looked at him twice."
The title "Wire in the Blood" is a phrase that comes from T.S. Eliot's "Four Quartets": "The trilling wire in the blood / sings below inveterate scars / appeasing long-forgotten wars." As for the meaning, in an interview Robson Green said the phrase was taken to mean a genetic kink, something impure and unusual in the blood, that leads to the kind of psychosis Dr. Tony Hill might deal with. Series writer Val McDermid says: "Who knows what Eliot really meant by that line? Robson's explanation is as good as any. For myself, I've always taken it to be a metaphor for the thrill of adrenaline surging through the bloodstream. But we'll never know for sure".