In reality, a witness in a federal court trial would be under the protection of the U.S. Marshals service.
The story was inspired by Senator Estes Kefauver's tactics in coercing Virginia Hill to testify in the Bugsy Siegel prosecution.
The characters Ginger Rogers and Brian Keith portrayed were supposed to be around the same age. In real-life, Ginger Rogers was over a decade older than Brian Keith.