He is the comatose father of A.J. Yates, a serial killer of women.
Dexter Morgan attempts to lure A.J. to him by phone. He pretends to be a doctor and tells A.J. that his father's condition has worsened and that he should hurry to say his goodbyes. When A.J. does so, Dexter corners him in his father's hospital room. A.J. then pulls the plug on his father's life support in order to create a diversion, allowing him to escape as several nurses rush to Mr. Yates's aid. It's unknown if he survives the incident.