Rollin uses a lamp, turntable and statuette to simulate the shadow of a man walking past a window. However, the shadow clearly moves like a real person, briefly pausing with each step.
The books on Lisa Goren's shelf, and the letters in her safe, are in English.
The guards in the courtroom wield Thompson submachine guns. Since the trial takes place in the Soviet Union, they should be wielding a Soviet weapon like the SKS-1945 rifle or the PPSh-41 submachine gun.
At the end when "Rollin" takes the stand and reveals he is Kushov, that gives the whole plot away as to how Briggs can be at two places at the same time.