The Streets of San Francisco Season 4 Episode 16

After being shot by robbers who were holding up a store, a young police officer is treated by a doctor who was on the scene. Unfortunately, the officer later dies, and the doctor becomes the only one who can identify the robbers. But when Stone and Keller try to call him, they find that he had to be using a phony name. The man has been practicing using the name of several different doctors.