Everything you need to understand or teach The Case of the Grinning Gorilla by Erle Stanley Gardner.
Gardner's fiction is not thematically sophisticated, because he strove to write novels that would be enjoyable and quick reading. Part of the appeal of the Perry Mason novels is the theme of the underdog overcoming adversity.
Another significant theme is that of the law as something that often works against unsophisticated people. The agents of the law, such as police lieutenant Tragg and district attorney Hamilton Burger, are usually more interested in convictions...