Dix is a former homicide Detective of the Gotham City Police Department, as well as being the former partner and mentor of Harvey Bullock.
Ten years previous, Dix was on duty with Bullock when the two of them got a tip about the hideout of Randall Milkie, a psycho terrorizing Gotham's elite as the killer known as the "Spirit of the Goat". Dix called for, and wanted to wait for, back-up since his personal mantra was "Gotham's Golden Rule - No heroes." Harvey, however, was unwilling to lose another victim to this fruitcake, and the two men headed in. Milkie had his stage set for his would-be captors and the young woman was already long dead. Trying to take down the killer, who reiterated that he was the Goat and no longer Milkie, Dix was left up on the stage when Milkie opened a trap-door and sent him plummeting to the ground, leaving him paralyzed from the waist down.
Helping Bullock and Gordon
A decade later, the Spirit of the Goat found a new "host" and the killings were once again in the headlines. Captain Sarah Essen ordered Bullock, and his partner James Gordon, to 'consult' with Dix, to find out if he told anyone about a suppressed detail of the original killings, or had any leads. Bullock wanted to leave his old partner out of it, but could not ignore a direct order. When they visited the older man in his nursing home, Dix reminded Harvey of the "no heroes" rule and warned Gordon that his partner had a white knight complex, always trying to make everything right. This was not Gordon's view or experience of Bullock and gave him clear food for thought. Dix was convinced that he and Harvey had been wrong the first time out and that Milkie was part of a larger conspiracy, hence the details of the killings being known to others.