Why does Dr. Armstrong decide to talk about their situation with Lombard instead of Wargrave?

From the text:

As before, the doctor hesitated for a moment His eye rested speculatively on Mr. Justice Wargrave. He wanted to consult with some one. He was conscious of the judge’s acute logical brain. But nevertheless he wavered. Mr. Justice Wargrave might have a good brain but he was an elderly man. At this juncture, Armstrong felt what was needed was a man of action.