William Wellman's "Public Enemy" is a tour-de-force performance by James Cagney, wrapped within some elegant direction, a solid supporting cast and a simple but effective screenplay.
The Public Enemy, along with two other films released in the early 1930s - Little Caesar and Scarface, set the standard for gangster genre. This was the film that made James Cagney a star. Ironically Cagney was originally cast to star as the Matt Doyle, the sidekick to Tom Powers, portrayed by Edward Woods. When Director William A. Wellman saw Cagney in rehearsals, he realized that Cagney would be far more effective in the star role than Woods, so he switched them and the rest is cinematic history.
Very good supporting cast formed by actresses who subsequently would have an important starring roles of their own: Jean Harlow and Joan Blondell. Mae Clarke became known for her scene with Cagney, in his striped pajama, sat opposite Mae Clarke at breakfast and decided he had had enough of her nagging and pressed half a grapefruit into Clarke's face.
Donald Cook was well cast as Powers' brother Mike who returns from World War I shell shocked, but able to discern the gangster that his brother has become. Beryl Mercer is equally good as Powers' mother who does not have the foresight to see that her son's path will lead to his impending demise.
One thing that is not clear is why Powers, in a hospital after being wounded in a gun-fight, is not under police arrest. In the end he is kidnapped from the hospital and, in a scene that could only be allowed in a time before the studios' production Code, is dumped dead on his doorstep.