The comic relief added from the constant nagging between Miss Plimsoll and Sir Wilfred is much needed in the ever tense scene in the courtroom. One can feel the pressure building by the look on Leonard Vole's face. .
Leonard Vole, although the main character in both the short story and the movie, plays somewhat different roles in each version. In the short story, Vole denies knowing anything about the money left to him in Miss Emily French's will. And in the movie, he is totally overjoyed at hearing the news. Overall, Leonard Vole plays the same role in the movie and the short story.
Leonard Vole's wife, Romaine in the short story and Christine in the movie, has varying roles. Romaine is from Austria. It is not told how she and Vole met, however we do find out the Romaine has a husband. He is in an insane asylum in Austria, which is why she never mentioned him to Vole. Her marriage to Vole is not legal. Christine is from Germany. It is told that she and Vole met in Germany during WWII. Christine was a cabaret dancer in a local bar where Vole came to have a drink one night. The rest is history. Christine never told Vole about her husband though. He was in East Germany fighting the war at the time. She felt it was not a big deal and wanted desperately to leave .
Germany. A marriage license is brought to court as proof of her marriage, signifying her marriage to Vole is not legal.
In both versions of "Witness for the Prosecution", Romaine/Christine ends up testifying against Vole. At first she had told Sir Wilfred/ Mr. Mayherne that she would testify for Vole. She backed up what he said as far as being home at the time of the murder and not leaving at all that night. Then in court she changes her story. She tells the court that Vole was not home at the time of the murder. This took the court by surprise. Something unexpected happened during the course of the investigation. Mr. Mayherne gets a call from an elderly woman.