Dr. Haile O'Connor was a coroner who worked at a morgue near the 23rd Precinct. He often examined bodies associated with cases detectives at that precinct were working on.
He's also been known to fantasize about getting into Elisa Maza's pants while discussing mutilated corpses with her.
Elisa seemed to have a small crush on him too, and was a little jealous when she saw him "getting busy" with his stepsister, Colleen at the Greasy Spoon. Haile corrected her saying that the "chick" was his stepsister. He did not deny that he was "getting busy with her" though.