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 than in untangling the complicated legal webs that have ensnared the innocent. The hostility between the district attorney and police on one side and Perry Mason and the private detective Paul Drake on the other is a common theme in the Perry Mason mysteries.
Another theme that recurs in Gardner's novels is that of altered states of consciousness. Gardner seems interested in the legal ramifications of crimes committed by people who are not in control...