Sportswriter Bill James wrote an interesting book called Popular Crime that covers most of the murder stories that gripped the American imagination from George Washington's time till the present. In the book, James makes an interesting point about the difference between how we used to investigate murders centuries ago versus how we investigate them now.
Before police regularly began taking forensic evidence, their main method for solving murders was figuring out who had a good motive to commit the crime and then throwing that person on the witness stand to see if they could make the charges stick. Unfortunately, being able to prove that someone wanted to commit a crime is a far cry from proving that they actually did it. As a result, there used to be a lot of trials but few convictions.
In contrast, now that we have forensic evidence there's a much higher conviction rate. However, it's also much, much more expensive to have a trial because of all the work that goes into gathering and testing that evidence. Furthermore, procedural crime shows have given people unrealistic expectations about how much evidence the police will be able to provide, so even a strong case might fail to persuade a jury that has no idea about what a strong case actually looks like. As a result, only a small number of slam dunk cases ever go to trial, because prosecutors generally don't want to waste the time and money that would be involved in taking an iffy case to trial.
Add those up and you get a clear picture: a lot of people have gotten away with murder over the years. Which is why Double Indemnity's insistence that murderers are doomed to pay for their crimes feels pretty silly.
Double Indemnity is a classic noir from 1944, directed by the versatile Billy Wilder. It's about an insurance man named Walter Neff who tries to sell a car insurance policy to a house wife named Phyllis only to find himself getting sold on a more dubious proposition: Phyllis convinces Neff to help her take a big insurance policy out on her husband and then bump him off. At first Walter wants no part of it, because he knows that the man who will investigate her claim has an incredible nose for sniffing out fraud, but eventually Neff's greed gets the better of him. The two conspirators plan the crime down to the smallest detail and it goes off without a hitch... but still the bloodhound smells something fishy.
It's a classic story of a man brought low by his own hubris, and the overall plot is dependable, if predictable. The problem is the way the story is told. To start with, the film's absolute insistence that the investigator is infallible is pretty ridiculous. Apparently, in this world insurance companies hire Sherlock Holmeses to be their fraud investigators, then they only ask them to work one case at a time and they allow their detectives to put as many hours and as much money behind an inquiry as the want. Well, of course if you have an investigator who is infallible, determined, unhurried and never overworked, they might always catch their man, but how often does that really happen?
It's also a little silly how much emphasis they put on the investigator's brilliance when Walter's real undoing is that he's an idiot. He concocts this elaborate plan, and he goes through all of this effort to be sneaky, but then the story he invents to explain how the husband broke his neck is "he tripped and fell off a train that was going 15 miles an hour." Fifteen miles an hour? Really? You were willing to go to all the trouble of never being seen in public with his wife during the entire time you were planning this crime, but you couldn't go to the trouble of waiting till the train built up some steam? Maybe the investigator smelled something fishy not because he's a genius but because your cover story stinks?
Mind you, I'm not objecting to the fact that their criminal plot comes undone. I understand that murderers do get caught, and I also understand that because of the censorship codes of the time the guilty had to get their just desserts in the end. I'm mostly annoyed by the smugness of the way the film shows the plot coming undone. Double Indemnity acts as if Neff's fate was sealed the moment he met Phyllis, when in fact, anything could have happened, because there are a lot of ways someone could get away with murder. If the film had been less heavy on the foreshadowing it might have felt more exciting, but instead, it wanted to emphasize Neffs doom, and that gave the film a clockwork feel that was kind of a drag.
Walter's mistake wasn't thinking that he could game the system with his insider knowledge, his mistake was being a character in a movie where the system always wins. Unfortunately, that system doesn't really work in the real world. Just ask Lizzie Borden and O.J. Simpson, two people who were accused of murder in very high profile cases - and both of whom left their murder trials with their freedom intact.