Who is Sgt. Duffy in the story, "SORRY WRONG NUMBER"?

Sergeant Duffy heads up the night shift at Precinct 43. He communicates with Mrs. Stevenson by telephone, and he doesn't seem to be overly concerned with her report. He is, however, responsible for planting the idea in Mrs. Stevenson's head that she might be the murder victim. Sergeant Duffy is described as disinterested and apathetic.