Right away, there is a conflict of interest. Probably the District Attorney's Office handling the investigation at all would be a conflict, especially in a smaller office like the one depicted in the movie. Normally, such a case would be handled by the state Attorney General's Office. Rusty has an even greater conflict than Carolyn's other colleagues because he had an illicit affair with her. Rusty does not disclose his affair to his boss (even when the boss confides his own affair to Rusty), which creates a greater appearance of impropriety.
The movie does a good job of showing the different roles and obligations of prosecutors and defense attorneys. The main character is a prosecutor who is charged with a crime. The movie shows his interactions with his hired defense attorney, played by Raul Julia. It shows advice given by the defense attorney to his client, like pleading the Fifth in the grand jury, even though his client may not want to take it. It also explains why he should do so even though it will make him look guilty - you don't want to give the prosecution pre-trial statements to use against you. The movie also shows strategic decisions made by the defense attorney along the way.
There is a part in the movie where the prosecutor wants to put in evidence statements that Rusty made to him. The judge correctly rules that the the prosecutor will not be permitted to testify in the case unless he steps down as prosecutor and lets someone else take over the case. This points to a key mistake that many books, TV shows, and movies make, which is having the attorney investigate crimes and question witnesses alone. That's what investigators are for. (Learn more about this in my free ebook revealing the Top 7 Mistakes Made by Writers of Crime, Mystery and Legal Drama.)
"Presumed Innocent" also shows the practical reality that sometimes things outside the courtroom can make all the difference in the outcome of a case. (SPOILER ALERT) In that case it was the defense attorney's knowledge of the trial judge's past unethical behavior that gave the defense an edge.
The movie can be used as a good example of how to show probable cause to get a search warrant. In the movie, the police had Rusty's fingerprints on a glass in Carolyn's apartment, phone records showed many calls between Rusty and Carolyn, including one call the night of the murder, Rusty's blood type matched semen found inside the victim (the book and movie were pre-DNA), and unknown carpet fibers were found in the victim's apartment.
NOTE, however, that the police in the movie choose not to search for a murder weapon. In reality, the police will always search for a murder weapon at the home of their primary suspect. (The reason this is done in the movie is because a twist at the end revolves around discovery of the murder weapon.)
Finally, there are two incidents in the movie where Rusty destroys evidence. That is obviously a big no-no -- for an attorney or anyone else.
This is one of the few examples of a movie that gets most of the legal stuff right. (It would probably be my second choice of an accurate legal film after My Cousin Vinny.) It is also a compelling story that stands up to the test of time. The book upon which the movie is based, also called "Presumed Innocent" by Scott Turrow, is excellent as well. (Click below to check out the movies or book.)
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