Anatomy of a Murder is a court room drama that draws out the many ways in which the law is compromised by the human beings upon which it relies and who rely upon it (e.g. whether or not a witness' testimony is truthful, whether an expert's testimony is indeed factual, etc). Whether an individual is judged as guilty or not seems to have less to do with actual guilt and more to do with a lawyer's ability to harness and manipulate the law and those called to testify, the judge's inclinations and predispositions, the degree of the jury's sympathy, etc. In the end, the audience becomes more interested in who will win than if the man accused of committing murder is guilty or not, which proves the point of the movie.
Jimmy Stewart gives a fantastic performance, acting the part of a charismatic and intelligent lawyer who plays the room by chopping the prosecutor's case off at the knees using small town rhetoric. He continually draws their attention away from the facts through dramatic outbursts. In contrast, the prosecution seems boring, uncharismatic, and even sinister.
Summary from IMDb:
In a murder trial, the defendant says he suffered temporary insanity after the victim raped his wife. What is the truth, and will he win his case?