Ignatz Theodor Griebl: The Nazi Spy Who Escaped Thanks to the Polygraph
The FBI’s first documented use of the polygraph in an espionage investigation came in 1938 in connection with a Nazi German spy ring operating in the United States. The most important suspect interrogated with the polygraph was Dr. Ignatz Theodor Griebl, a medical officer in the U.S. army reserve who is believed to have been …