Howard Green is credited with the screenplay, and Hecht and MacArthur are uncredited as helping on it. I suspect the latter two responsible for one interesting moment in the film. Martin Kosleck has just killed one of the other characters in the New York Subway. He has just left the subway station when he runs into an old acquaintance from Europe. It turns out this old acquaintance is still a policeman. Kosleck, realizing his past misdeeds are about to catch up with him, flees but is killed by the cop.
Would you believe this almost happened?
Hecht and MacArthur had contacts with the police and newspapermen in Chicago (remember "THE FRONT PAGE") and New York. They probably heard of this incident from their contacts. In 1918 during the closing days of World War I, the story came out of Austria of a serial killer (or women) named Bela Kiss. He was being sought for his murders, but was believed to have joined the army and been killed in battle. Subsequently it turned out that Kiss was smart enough to change his identity cards with a dead man, so he was still alive. But he was not caught. Then in 1930 a Detective on the New York City Police Force saw Kiss leaving a subway station in Times Square. The Detective tried to catch him, but the crowd enabled Kiss to escape. Kiss (as it turned out) had immigrated under a fake name to the U.S., and settled as a janitor in an apartment house in the Yorkville area of Manhattan! He died about 1957 (in bed!). I wonder if he ever saw THE MAD DOCTOR and Kosleck's last scene.